WO2004009433A1 - Motorcycle engine - Google Patents

Abstract

A motorcycle engine (20) is disclosed for mounting in a motorcycle (10) such that cylinders (80) in the engine are all inclined towards the rear of the motorcycle. This configuration can allow the engine to be mounted further forwards in the motorcycle, giving rise to advantages in the design of the motorcycle, including allowing a more compact engine. Further aspects include features of a powertrain of such a motorcycle, including components of the engine, and further components of such a motorcycle or engine.

Description

MOTORCYCLE ENGINE

Aspects of the invention relate to an engine, and further examples relate in particular to an engine suitable for a production (or road) motorcycle. Yet further aspects relate to features of a powertrain of such a motorcycle, including components of the engine, and to further components of such a motorcycle or engine.

Engines for motorcycles are known which provide generally reliable performance when used in road vehicles, and in competitions such as the Britisb-or World Superbike Championship . -In such applications, it-is-advantageous-for-the engine to be small and light and to have a weight distribution allowing the centre of gravity of the whole motorcycle to be situated precisely. It is an aim of the present invention to provide improvements in some of these characteristics.

In accordance with a first aspect of the invention, there is provided a motorcycle having a single- or inline multi-cylinder engine mounted to a chassis thereof, said engine having an air inlet aperture, wherein the inlet aperture faces the front of the motorcycle.

In particular examples, such an engine is provided in a "production" motorcycle or a "road" motorcycle.

In accordance with a second aspect, there is provided a motorcycle having a single- or inline multi-cylinder engine mounted to a chassis thereof, wherein the or each cylinder of the engine is inclined towards the rear of the motorcycle.

In accordance with a further aspect, there is provided a system for supplying air to a motorcycle engine, said system comprising an air intake and means for conveying air from the air intake to an engine, wherein the conveying means has a length less than twice the direct distance between the engine and the air intake.- In accordance with a further aspect, there is provided a system for exhausting gas from a motorcycle engine, said system comprising an exhaust canister and means for conveying gas from an engine to the exhaust canister, wherein the conveying means has a length less than twice the direct distance between the engine and the exhaust canister.

In accordance with a further aspect, there is provided an engine comprising a crankshaft and a gearbox having an output sprocket, comprising means for causing the crankshaft and the output sprocket to rotate in opposing directions.

In accordance with a further aspect, there is provided a motorcycle having an engine mounted to a chassis thereof, said engine comprising a crankshaft and a balancing shaft, wherein the balancing shaft is disposed between the crankshaft and the rear of the motorcycle.

In accordance with a further aspect, there is provided an engine comprising a clutch primary and a balancing shaft having means for driving the clutch primary.

In accordance with a further aspect, there is provided an engine comprising an idler shaft having driven means for driving the idler shaft and driving means for driving a clutch primary, a gearing ratio between the driven means and the driving means being greater than 1..

In accordance with a further aspect, there is provided a balancing shaft comprising a driven gear for driving the balancing shaft and a driving gear for driving a clutch primary.

In accordance with a further aspect, there is provided an engine comprising a cylinder having an inlet port and an outlet portrwherein theinlet port and/or the outlet port is disposed at an angle ofgreater than 25° to-a -longitudinal ax-is-øf-the-eylinder-r- In accordance with a further aspect, there is provided an engine comprising a cylinder having an inlet port and an outlet port, wherein the inlet port and/or the outlet port is disposed at an angle of greater than 30° to a longitudinal axis of the cylinder.

In accordance with a further aspect, there is provided an engine comprising a cylinder having an inlet port and an outlet port, wherein the inlet port and/or the outlet port is disposed at an angle of greater than 35° to a longitudinal axis of the cylinder.

In accordance with a further aspect, there is provided an engine comprising a cylinder having an inlet port and-an-outiet port,- wherein the inleLpbr rand ox_me^utlet_portis disposed at an angle of greater than 40° to a longitudinal axis of the cylinder.

In accordance with a further aspect, there is provided an engine comprising a cylinder having an inlet port and an outlet port, wherein the inlet port and/or the outlet port is disposed at an angle of greater than 45° to a longitudinal axis of the cylinder.

In accordance with a further aspect, there is provided an engine comprising a cylinder having an inlet port and an outlet port, wherein the inlet port and/or the outlet port is disposed at an angle of greater than 50° to a longitudinal axis of the cylinder.

In accordance with a further aspect, there is provided an engine comprising a cylinder having an inlet port and an outlet port, wherein the inlet port and/or the outlet port is disposed at an angle of greater than 55° to a longitudinal axis of the cylinder.

In accordance with a further aspect, there is provided an engine comprising a cylinder having an inlet port and an outlet port, wherein the inlet port and/or the outlet port is disposed at an angle of greater than 60° to a longitudinal axis of the cylinder.

In accordance with a further aspect, there is provided an engine comprising a cylinder and an inlet valve and an exhaust valve, -wherein the inlet-valve and/or the exhaust valve is disposed at an angle of greater than 5° to a longitudinal axis of the cylinder. In accordance with a further aspect, there is provided an engine comprising a cylinder and an inlet valve and an exhaust valve, wherein the inlet valve and/or the exhaust valve is disposed at an angle of greater than 7° to a longitudinal axis of the cylinder.

In accordance with a further aspect, there is provided an engine comprising a cylinder and an inlet valve and an exhaust valve, wherein the inlet valve and/or the exhaust valve is disposed at an angle of greater than 11° to a longitudinal axis of the cylinder.

In accordance with a further aspect, there is provided an engine comprising a cylinder and an inlet valve and an exhaust valve, wherein the inlet valve and/or the exhaust valve is disposed at an angle of greater than 13° to a longitudinal axis of the cylinder.

having a stroke and a connecting rod, wherein the connecting rod has a length of substantially twice the stroke.

In accordance with a further aspect, there is provided an engine comprising a coolant pump, wherein the coolant pump is mounted on a cylinder block of the engine.

In accordance with a further aspect, there is provided an engine comprising a coolant pϋrnpTwherein tlre^™pumpts^~driven by gears^~from^~a crankshaft of the engine.

An aspect of the invention provides a motorcycle engine comprising at least one cylinder, wherein^" the engine is adapted to be mounted in a motorcycle such that the cylinders are all inclined towards the rear of the motorcycle.

According to this aspect, in a single cylinder engine, the cylinder is inclined towards the rear of the motorcycle; for a multicylinder engine, all of the cylinders are inclined towards the rear of the motorcycle. This^" configuration may allow the engine to¹ be mounted furtherforwards iirthe motorcycle which-cairgive-rise-to-advantages in the design of the motorcycle. In some cases, this may also give rise to a more compact engine.

It will be understood that preferably the angle of the engine in the motorcycle relates to the angle when the motorcycle is standing upright at rest on a horizontal surface.

Preferably the angle of inclination of a cylinder is between 12 degrees and 18 degrees to the vertical. Preferably the angle is measured between the vertical and the longitudinal axis of the cylinder. In preferred examples, the angle is between 13.5 degrees and 16.5 degrees. Preferably the angle of inclination is about 15 degrees.

Preferably in a multicy Under engine, all of the cylinders are inclined at the same angle to the vertical.

Preferably each cylinder -is associated with a respective inlet aperture, the engine being adapted to be mounted in a motorcycle such that the inlet apertures face generally forwards.

A further aspect of the invention provides a motorcycle engine comprising a plurality of cylinders, each cylinder being associated with a respective inlet aperture, the engine being adapted to be mounted in a motorcycle such that the inlet apertures face ^"genefally forwards:

Where reference is made to the inlet apertures facing generally forwards, it is preferably to be understood that the apertures do not face towards the rear of the motorcycle as is the usual configuration.

Such a configuration may confer the advantage that the intake of air into the engine is more direct, potentially giving rise to improved combustion efficiency and greater power output.

Preferably each cylinder being associated with a respective exhaust aperture, the engine being adapted to be mounted in a motorcycle such that the exhaust apertures face generally rearwards.

A further aspect of the invention provides a motorcycle engine comprising a plurality of cylinders, each cylinder being associated with a respective exhaust aperture, the engine being adapted to be mounted in a motorcycle such that the exhaust apertures face generally rearwards.

Such a configuration may give rise to the advantage that the exhaust system, which will become heated, is disposed away from the airbox of the motorcycleT

Preferably the engine comprises an inlet aperture and an inlet passage in flow

further 'comprising means for varying- the length of the inlet passage.

A further aspect of the invention provides a motorcycle engine, comprising an inlet aperture and an inlet passage in flow communication with the inlet aperture, the engine further comprising means for varying the length of the inlet passageT

Variable inlet length may give rise to the advantage that the engine may be dynamically tuned^"during^"operation rat various speeds. ^'

Preferably the inlet passage comprises a throttle body mounted adjacent the inlet aperture and a trumpet movable mounted on the throttle body.

Preferably the trumpet is slidably mounted on a guide shaft having a longitudinal axis disposed parallel to a longitudinal axis of the throttle body.

Preferably the length adjusting means comprises an actuator for sliding the trumpet- in a longitudinal direction on the guide-shaft. - A further aspect of the invention provides a motorcycle engine comprising a cooling system including a plurality of coolant passages for passing coolant through portions of the engine, wherein a first set of coolant passages having a first cross-sectional area and a second set of coolant passages having a second larger cross-sectional area.

Such a system may give rise to the advantage that the flow of coolant in the first set of passages is faster than in the second set of passages, thus giving greater cooling in the region of the first set of passages. Preferably, the first set of passages are arranged adjacent areas requiring particular cooling, for example areas closer to the combustion chamber and the exhaust system such as the valve seats, the upper end of the cylinder block, the valve guides and so on.

A set of passages preferably comprises one passage or a plurality of linked passages.

Preferably the engine further comprises a third set of coolant passages.

In a particular example, the engine may comprise a first set of passages adjacent the valve guides, a second set of passages adjacent the valve seats and a^"mird^~set^~δF passages adjacent the upper end of the cylinder block (that is, adjacent the combustion chamber). This may allow different coolant flow rates in these areas. In particular, ^{" "} it may allow the level of cooling to be tailored to the level of cooling required in these areas.

Preferably the engine comprises a coolant passage for passing coolant adjacent valve guides of the engine. Preferably the engine comprises a coolant passage for passing coolant adjacent valve seats of the engine. Preferably the engine comprises a coolant passage for passing coolant adjacent a portion of a cylinder housing of the engine adjacent a combustion chamber.

Preferably the engine comprises a cooling system, wherein the cooling system is adapted to be pressurised. Such a cooling system may give rise to enhanced flow and cooling characteristics.

Preferably the engine has a fuel injector arranged upstream of a throttle valve. Injecting fuel upstream of the throttle valve may confer the advantage of enhanced power/torque output. Further flexibility may be achieved by providing additionally an injector downstream of the throttle valve.

Preferably the engine comprises a pneumatic valve. Pneumatic valves may allow for higher speed operation^" of the engine. This feature is particularly important and may be provided independently.-

Preferably all of the exhaust and inlet valves comprise pneumatic valves. :It ι tiv^~ely7^"aτ^m^{^}^ mechanisms (for example coil- springs) may be used. For example, where the inlet valves are of different weights to the exhaust valves, pneumatic valves are preferably used on the heavier valves.

A cylinder may have two inlet valves and two exhaust valves associated therewith. Alternatively, a cylinder has three inlet valves and two exhaust valves associated therewith.

Other arrangements might be used. For a multicylinder engine, generally all of the cylinders will have the same inlet valve arrangement and the same exhaust valve arrangement;

A further aspect of the invention provides an engine comprising a plurality of cylinders, each cylinder having a cylinder liner, wherein the cylinder liners are joined together.

This ma giveTiseHra more ompact eτιgine"structure. It may further allow the liners to be extracted together, which may also be advantageous. In a particularly preferred arrangement, the liners of all of the cylinders are joined together in a single unit. However, in other arrangements, fewer than all of the liners may be joined together. The liner may, for example, be formed of a light Aluminium alloy such as A7075.

A further aspect of the invention provides an engine comprising a connecting rod having a coating at at least one end.

Such a coating ^"may confer the" advantage that the region to which it is applied may have properties other than the bulk properties of the connecting rod. In particularit may serve to reduce friction. Preferably, the connecting rod has a coating in a region in which it may contact another surface.

Preferably the coating is at the small end of the connecting rod.

This is particularly advantageous where the thrust is carried at the small end of the connecting rod.

Preferably the connecting rod comprises titanium.

Inaparticύlar preferred emb'odiment the connec^"ting^~rodϊs formed largely of titanium and preferably further has a coating of, for example, molybdenum or CrN, preferably at the small end. This may be particularly advantageous in an engine having a piston formed of aluminium. This may reduce the likelihood of undesirable interaction- between the surfaces of the connecting rod and the piston. Preferably, the piston comprises forged aluminium.

Preferably the connecting has a length of less than 100mm. Preferably the connecting rod has a length of less than 95mm. Such short connecting rods may give rise to a more compact and lighter engine. Preferably the engine comprises a connecting rod and arranged such that lateral thrust of the connecting rod is born at the small end thereof. This important feature may also be provided independently.

A further aspect of the invention provides a motorcycle engine according to any of the preceding claims, comprising a clutch having a clutch plate comprising a carbon fibre material.

Preferably the clutch is adapted to allow some backslip. Thus, the clutch can reduce the effect of engine braking transmitted to the rear wheel of the motorcycle, resulting in a reduced likelihood of the rear wheel locking in extreme conditions. Preferably, the clutch is adapted to allow backslip when the load on the clutch reaches a

activate the.backslip. This may confer the further advantage that the characteristics of a motorcycle may be tailored to the requirement or preferences of a particular rider.

Preferably the engine comprises a crankshaft having an axis of rotation, and means for introducing oil into an inlet of a bore in the crankshaft, wherein the inlet is located in^" the region of the axis of rotation of the crankshaft.

Introducing oil into the crankshaft in the region of the axis of rotation may confer the advantage thatitisjiot necessaryjo^overcome cjentrifugaliorces in order to introduce the oil. This important feature is also provided independently.

Preferably the engine comprises a seal associated with the inlet, wherein the seal comprises a magnetic seal.

The use of a magnetic seal may confer the advantage that the integrity of the oil feed through the crankshaft is maintained even at high rotational speeds of the crankshaft.

Preferably the engine includes a plurality of cylinders. A further aspect of the invention provides a motorcycle including a motorcycle engine as described herein.

A further aspect of the invention provides a connecting rod having a coating at at least one end. Preferably the coating is at the small end of the connecting rod. Preferably the connecting rod comprises titanium. Preferably the connecting rod has a length of less than 100mm, preferably a length of less than 95mm.

A further aspect of the invention provides a ^"clutch for a motorcycle, wherein the clutch is adapted to allow some backslipv -

A further aspect of the invention provides a crankshaft for a motorcycle engine, the crankshafthaving an axis of rotation, and including means for introducing oil into an inlet of a bore in the crankshaft, wherein the inlet is located in the region of the axis of rotation of the crankshaft.

A further aspect of the invention provides a crankshaft arrangement for a motorcycle having an oil inlet and a seal associated with the inlet, wherein the seal comprises a magnetic seal.

^{~ ~}furthΕr^~asp^~e^ an engine for a motorcycle,—

A further aspect of the invention provides a motorcycle comprising an intake having an elongate mouth feeding an intake duct which passes through a headstock of the motorcycle. The intake mouth is preferably generally horizontal.

The invention extends to methods and/or apparatus substantially as herein described with reference to the accompanying drawings.

While the examples herein have been described in the context of motorcycles, it will be appreciated that aspects of the invention are equally applicable to engines for other applications.

Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied to apparatus aspects, and vice versa.

Preferred features of the invention will now be described, by way of example only, with reference to the; accompanying drawings, in which:

Figure 1 is a sketch illustrating the side elevation of a motorcycle, showing the general position and attitude of an engine;

Figure.2B is a-left side elevation-of the engine shown in Figure 2A; Figure 2C is a front elevation of the engine shown in the Figures 2 A and 2B;

Figure 2D is a rear elevation of the engine shown in Figures 2 A to 2C;

Figure 2E is a plan view of the engine shown in Figures 2 A to 2D;

Figure 3A is an underside view cross-section of a cylinder liner;

Figure 3B is a side view cross-section of the cylinder liner shown in Figure 3A; Figure 4A is a plan view of a cylinder head of an engine;

^"figure^" 4B^"ls a"cros^^ heatTaTong the line A- A shown in Figure

4A; .

Figure 4C is a cross-section of the cylinder head along the line B-B shown in Figure

4A; Figure 5 is a cross-section of a fuel rail with injectors;

Figure 6A is a dimensioned plan view of a cylinder head;

Figure 6B is a dimensioned cross-section of the cylinder head along the line A-A shown in Figure 6A;

Figure 6C is a dimensioned cross-section of the cylinder head along the line B-B shown in Figure 6A;

Figure 6D is a dimensioned cross-section of the cylinder head along the line M-M shown in Figure 6 A;

Figure 6E is a dimensioned cross-section of the cylinder head along the line C-C shown in Figure 6 A;

Figure 6F is the inlet aperture of the cylinder head shown in Figure 6A; Figure 6G is the exhaust aperture of the cylinder head shown in Figure 6A;

Figure 7 is a crankshaft of an engine;

Figure 8 is a balancing shaft of an engine;

Figure 9 shows the gears by which the crankshaft drives the balancing shaft, which in turn drives the clutch primary gear; Figure 10 is a schematic diagram-o -a- connecting rod between a piston and a crankshaft;

Figure 11 A is a front elevation of a connecting rod of an engine;

Figure^~l^"lB^"ϊs^~a: side^"el v iurrof^" me^θ^'mιe ntn^rod^"ΕhOwπ^"in^_Fιgure 11 A; - -Figure 11C is a cross=section-.of-the-connecting-rod-along the line A-A shown in Figure 11 A;

Figure 1 ID is a detailed view of the big end of the connecting rod shown in Figures

HA to llC;

Figure 12A shows the underside of a piston, highlighting indented regions in the surface; Figure 12B shows the underside of the piston shown in Figure 12 A, in which dimensions are^'iή licated'^™

Figure 13 A- is a plan view of a piston of an engine;

Figure 13B is a side elevation of the piston shown in Figure 13 A, viewed in the direction of arrow "Z" shown in Figure 13A; Figure 13C is a cross-section of the piston shown in Figures 13A and 13B, viewed along the line A-A shown in Figure 13 A;

Figure 13D is a cross-section of the piston shown in Figures 13 A to 13C, viewed along the line B-B shown in Figure 13C;

Figure 13E is a cross-section of the piston shown in Figures 13A to 13D, viewed along the line C-C shown in Figure 13C;

Figure 13F is a side elevation of the piston shown in Figures 13 A to 13E, viewed in the direction of arrow "Y" shown in Figure 13 A;

Figure 14A is a plan view of a piston of an engine, together with two side elevations in the directions indicated on the diagram;

Figure 14B is a cross-section of the piston shown in Figure 14A, viewed along the line A-A shown in Figure 14A;

Figure 15 A is a plan view of a piston of an engine, together with two side elevations in the directions indicated on the diagram and two cross-sectional views along the lines L-L and M-M indicated on the diagram;

Figure 15B is a cross-section ofthe piston shown in Figure 15A, viewed along the line A-A shown in Figure 15A;

Figure 15C is a cross-section ofthe piston shown in Figure 15A, viewed along the line

A-A shown in Figure 15 A, showing details ofthe piston ring groove and oil groove;

Fϊgure^~l^"6 is a scheTn^u^dia^Hm^^"irfronrelevation of a motorcycle;

-Figure 17 is a schematic cross-sectional-view of a motorcycle air intake; Figure 18 A is a front elevation of an engine, indicating features of the variable intake trumpets;

Figure 18B is a right side elevation of the engine of Figure 18 A, indicating features of the variable intake trumpets;

Figure 19 is a schematic diagram of the lubrication system of an engine; Figure 20 shows the central oil feed to the crankshaft;

Figure 21 is a^" schematic liagranϊof system;

Figure 22 is a schematic diagram of a drive-by- wire throttle control system;

Figure 23 A is a left side elevation of an engine;

Figure 23B is a front elevation ofthe engine shown in Figure 23A; Figure 23C is a plan view of the engine shown in Figures 23 A and 23B;

Figure 24A shows two pneumatic valve spring assemblies;

Figure 24B is a cross-section through the line A-A shown on Figure 24A;

Figure 25 is a sketch of a cross-sectional side elevation of a cylinder head and combustion chamber of an engine; Figure 26A is a front elevation of a connecting rod of an engine;

Figure 26B is a side elevation of the connecting rod shown in Figure 26 A; Figure 26C is a cross-section of the connecting rod along the line A-A shown in

Figure 26A;

Figure 26D is a detailed view of the big end of the connecting rod shown in Figures

26A to 26C; Figure 27 is a side elevation of a motorcycle, showing the position and attitude of the engine;

Figure 28A is right side elevation of the engine;

Figure 28B is a left side elevation of the engine shown in Figure 28 A;

Figure 28C is a front elevation of the engine shown in the Figures 28 A and 28B; Figure 28D is a rear elevation of the engine- shown in Figures -28 A to 28G;--—

Figure 28E is a plan view of the engine shown in Figures 28 A to 28D;

Figure 29A is a rear-right perspective view of the engine shown in Figures 28A to

28E; -

Figure 29B is a rearJeft perspective view ofthe engine shown in Figures 28A to 28E; Figure 29C is a further front elevation of the engine shown in Figures 28 A to 28E;

Figure 30 is a schematic view of a cylinder head of an engine, including a throttle body, an inlet trumpet, injectors and an exhaust port;

Figures 31 A and 3 IB are schematics of cylinder heads of an engine showing varying^" amounts of detail; Figures 32A is a schematic view of a cylinder head of an engine, and Figures 32B and

^"32C show the shape of inlet and exhaust apertures of the cylinder head;

Figure 33 shows the profile of inlejLpassages in a_cylinder head of an engine;

Figure 34 shows the profile of exhaust passages in a cylinder head of an engine;

Figure 35 shows a crankshaft and a balancing shaft of an engine; Figure 36 shows the gears by which the crankshaft of an engine drives the balancing shaft;

Figure 37A is an elevation of the driven end of the balancing shaft of an engine, showing the gear by which the balancing shaft is driven;

Figure 37B is a longitudinal cross-section of the balancing shaft of an engine; Figure 37C is a perspective view of the balancing shaft shown in Figure 37B;

Figure 38 is a schematic representation of the power train of a motorcycle; Figure 39 is a schematic representation of a cooling system of an engine; Figure 40 is a schematic representation of another cooling system of an engine; Figures 41 A to 41G show various views of a radiator of a cooling system; Figures 42A and 42B are side elevations of a motorcycle showing the position of the radiator and the coolant conduits between the engine and the radiator; Figure 43 is a schematic representation of the valve train of an engine; Figures 44A and 44B are perspective views of a motorcycle chassis showing the position of an airbox;

Figure 45 is a view of the underside of the chassis shown in Figures 44A and 44B, showing the aperture in the airbox in which the intake trumpets of the engine sit; Figure 46 is a cross-sectional view of a gearbox of an example; and Figure 47 is a schematic representation of an engine management system of an ^"example-: ^'

Three examples of engines will be described below.

A first example of an engine is now described in detail, with reference to Figures 1 to 22.

Figure 1 shows a motorcycle 10, illustrating the general location and attitude of the

^"engine 20. The^" engine^" 20 is mounted in a chassis, upon which are also mounted fairing components and a seat_and.so on, asis customar^._Atme.frojαtjD the_chassis, there is a headstock 13, to which is mounted the triple tree carrying the front forks and wheel. The swing arm carrying the rear wheel is mounted to the rear of the engine. In an alternative example, the swing arm may be mounted to the chassis.

In particularly preferred examples, the engine is for use in racing motorcycles, including motorcycles suitable for competitions such as the Federation Internationale de Motocyclisme (FIM) Motorcycle Grand Prix (MotoGP). In alternative examples, the engine is for use in production or road motorcycles,4ncluding-motorcycles suitable for Superbike competitions such as the World Superbike competition. Various features relating to the first engine, such as the orientation of the engine and cylinder head configuration; crankshaft and balancing shaft; pistons and connecting rods; cooling system; air intake; lubrication; gearbox, and engine management system will be described, following an overview of the engine.

Engine Overview

Five external views of an example of an engine are shown in Figures 2A to 2E, which are respectively a right side elevation, a left side elevation, a front elevation, a rear elevation and a plan view of the engine.

In overview, the engine is a four-stroke engine 20 comprising three cylinders 80a, 80b, 80c in an in-line configuration as shown in Figure 2C, each having a bore and Stroke of 94 mm and 47.5 mm respectively. This oversquare shape may enable the -engine to be run at higher-speeds. .

As may be seen from Figures 2A to 2E the engine is housed in an engine casing 22 which comprises a cylinder head cover 40 detachably located on a cylinder head 60.

The cylinder head 60 comprises three inlet apertures 70a, 70b, 70c (see Figure 4A) which are disposed (in contrast to known production and road motorcycles) on its forward side 62. Attached to the inlet apertures 70 are respective throttle bodies 100a,

"lOOb lOO r having re^ectiveintake-trumpets 120a, 120b; 120c. Each inlet aperture

70, throttle body 100- and trumpet- 120 feeds a respective cylinder 80 as further described below. In the rear side 64 of the cylinder head 60 are disposed three exhaust apertures 200a, 200b, 200c (see Figure 6G) to which are attached respective exhaust passages (not shown). The exhaust apertures 200 are fed by the combustion chambers via two exhaust ports (not shown) per cylinder as further described below.

Having the inlet apertures on the forward side ofthe engine and the exhaust apertures to the rear may allow the exhaust system and the intake^~system^"to be disposed at a distance from one another which may overcome"^"or allϋvi^"ate^""the^"piOblem in known

^•engines in which the intake air is heated by the exhaust gases due to the proximity of the systems to one another. In addition, the exhaust system is remote from the coolant and lubricant radiators (described below) which may result in less heat transfer from the exhaust system to the radiators. As a further result, the engine may be located further forward than in known motorcycles allowing for more flexibility in the location of the centre of gravity.

The cylinder head 60 houses two camshafts driving three inlet and two exhaust valves per cylinder.

Three cylinders 80 are formed by a single removable-'-'siamese triplet" cylinder liner, as shown in Figures 3 A and 3B. A cross-sectional view of the cylinder liner from below is shown in Figure 3A, while Figure 3B shows a cross-section of the liner

^"through a plane parallel to the longitudinal axes ofthe cylinders 80. The cylinder liner generally has the shape of three closely spaced circles whose centres lie on a common axis of symmetry, where each of these circles corresponds to one of the cylinders 80a, 80b or 80c. The cylinder head 60 contains a cavity ofthe same shape as the external surface of the cylinder liner 92, into which the liner is inserted. An interference fit between the cylinder head 60 and the liner ensures that the liner remains in place during operation ofthe engine. A flange 97 is provided around the external perimeter of the upper edge of the liner. The internal surfaces of the cylinder liner 96 have a circular internal ^"cross-section ^"which is honed to the precise bore ofthe cylinder. The cylinder liners are preferably- manufactured from-an-aluminium-allo-y-_^such-as-A7O-75_ which has a high tensile strength. The separation between cylinders is minimised by forming the three cylinders from liners located within a single cavity in the engine block, thus contributing to the overall compactness of the engine. Furthermore, worn cylinders may be replaced simply by replacing the cylinder liner, allowing the engine block to be reused.

Going back to, for example, Figure 2A, mounted on the right side of the cylinder block 24 is a water pump 300 for pumping "coolant around the^'eπgiπe. The cσoling system is also described in further detail below. An alternator specialised for use with engines operating at speeds in the order of 15,000 to 16,000 revolutions per minute is used to provide a supply of direct current to the electrical components of the motorcycle. Such an alternator may be obtained, for example, from Magneti Marelli.

Orientation of engine and cylinder head configuration

As indicated above, the engine comprises three cylinders 80 in an in-line configuration. The cylinders are arranged such that when the engine is mounted on the bike the cylinders are angled back from the vertical by 15°. In further examples this angle might be between 13.5° and 16.5°, and in still further examples, it might be between 12° and 18°. In yet further examples the angle may be up to 20° or 25^°. As a result, the inlet trumpets 120 point upwards to a greater degree. The relative

features ofτte^~engine irra particularly preferred example are described below with reference to Figures 4A to 4C.

Figure 4A shows a plan view o the cylinder head 60 of an example, illustrating the location of the three inlet valves 86, 87, 89 and two exhaust valves 91, 93, for each cylinder. Figures 4B and 4C show cross-sections of the cylinder head 60 along the lines A-A and B-B respectively, as indicated on Figure 4A. The cross-section shown in Figure 4B is taken through the centre of -the central inlet valve 87- and directly ^"ISeTwΕerrthe exhaust v^"aιves 90791^".

Figure 5 shows a cross-section of the fuel rail 506, upon which are mounted three injectors 502a, 502b and 502c. There is a single injector 502 for each cylinder 80 of the engine. Both the fuel rail 506 and injectors 502 may be standard components, for example provided by Magneti Marelli. Each injector 502 is disposed axially with respect to its respective throttle body 100 and trumpet 120 upstream of the throttle butterfly.

The axis of the trumpet and the throttle body is disposed"atan angle of 55τ5 ° from the- axis of the respective cylinder. Disposed between those axes, at an angle of 12.4° from the axis of the cylinder, is the inlet valve. The valves may be formed from titanium.

On the exhaust side of the cylinder head, the axis of the exhaust valve is disposed at an angle of 10.6° to the axis of the cylinder. The axis of the exhaust port is disposed at 51° from the axis ofthe cylinder. The two exhaust valves for each cylinder are in a parallel configuration.

The valve guides for each of the valves may be formed of a manganese-copper alloy and/or the valve seats may be formed of a copper-beryllium alloy. -

Naive coil springs are used to close both the intake and exhaust valves.

Incertain examples, such as motorcycles intended for use in races such as those ofthe Motorcycle Grand Prix, the gudgeon pins have zero offset. In other examples, such as motorcycles intended primarily for road use, the gudgeon pins have a non-zero offset.

Note that some examples (such as that shown) comprise three inlet and two exhaust valves per cylinder, and that in the discussion of the position of the valves above, ^""references to e^"axesOf^'te^~vdve p^"refeτably^"shall bejaken tOTffea aprojection of the axes-normally onto-me-plane-defined,-fonexample,_b-y- e-axes_^of_the_respective„ cylinder and the respective throttle body.

The valves (for example 86 and 90 in Figure 4C) are driven via tappets by dual overhead camshafts which are themselves driven by gears from the crankshaft 440 shown in Figure 7.

The faces of the valves 86, 87, 89, 91 and 93, a portion of the cylinder head, the piston crown and the cylinder sleeve 96 together define a combustion" chamber which communicates with the inlet and exhaust ports via the respective valves, when opened. In preferred examples, the combustion chamber is generally hemispherical. In a particularly preferred example, the spark plug is disposed centrally with regard to the roof of the combustion chamber.

The dimensions of an example are shown in Figures 6A to 6G. Figure 6A shows a plan view of a cylinder head. Figures 6B to 6E show cross-sections through the cylinder head along the lines marked in Figure 6A as A-A, B-B, M-M and C-C respectively. Figures 6F and 6G show the inlet apertures 70 and exhaust apertures 200 respectively.

In a particularly preferred example, various dimensions/angles of the cylinder head and associated features are precisely as marked in the figures and/or as described

^""iiereiπr Howeverfln^" further ^"examples;^" some ^~oτ-ali^"Of^" the dtπrensions/angles may

-differfrom those shown/described by plus or minus 25%, plus or minus 20%, plus or minus 15%, plus or minus 10%, plus or minus 5% or plus or minus 2%.

Crankshaft and balancing shaft

The engine 20 further comprises a crankshaft 440 (see Figure 7). The engine has an even firing order and the three crankpins 448a, b, c on the crankshaft 440 are equally spaced such that forces due to acceleration-of reciprocating components are largely fratancedin a known manner, either by each other or by extended webs 442 (which in a preferred example comprise heavy metal inserts) on the crankshaft. However, the outside two cylinders 80a, 80c produce an additional torque on the crankshaft which is not cancelled by the reciprocating masses ofthe pistons and so on or by theτotating masses of the extended webs 442.

To counter this torque, the engine 20 comprises a balancing shaft 460 (see Figure 8). The balancing shaft is driven by engagement of a gear 464 on the balancing shaft 460 and a gear 444 on the crankshaft 440. Gears 444 and 464 have the same size such that the balancing shaft 460 rotates at the-same-speed-as the crankshaft 440.- The balancing shaft comprises two balancing masses: the first mass 466 is a metal insert mounted in the gear 464, and the second mass 468 is near to the end of the balancing shaft remote from the gear 464. In the example shown in which the balancing shaft is used to drive the gearbox input shaft via the clutch, there is a balancing shaft primary gear 472 on the balancing shaft adjacent the balancing shaft driving gear 464. The balancing shaft primary gear 472 is arranged to mesh with a clutch primary gear 482 (as shown in Figure 9).

As can be seen (for example, in Figure 8), the first and second masses 466, 468 are disposed on opposing sides ofthe balancing shaft-460- In addition to-the effect of the first and second masses 466, 468, rotation ofthe balancing shaft 460 may additionally produce a torque as a result of one or more cavities or bores 474 in the gear 464 (or indeed in the further gear 472, although such cavities or bores are not shown).

In a particularly preferred example, the balancing-shaft-mounted balancing shaft driving gear 464 has a radius greater than that ofthe further gear 472. Additionally, the radius of the second mass 468 is greater than the radius of the further gear 472 (and in particular, the radius of the second mass 468 is greater than the radius of the dedendum circle of the balancing shaft primary gear 472). This may be achieved for example by forming the balancing shaft 460 as an assembly. A balancing shaft formed in c3ne piece ma^{^}y^"bepf0dύ ^d^"fήofe^h aply^{^}m^"an ^"a balancing shaft assembly, and it may be-more.stable.man-a-shafLassembled-froni-anumber_o arts.__

As mentioned above, the balancing shaft primary gear 472 on the balancing shaft 460 engages with the clutch primary gear 482. For this reason and since in the preferred example the gearbox 420 is rearward of the crankshaft 440, the balancing shaft 460 is to the rear, and slightly lower than, the crankshaft 440. The engine casing 22 has a single split (not shown) at approximately the level of the shafts to allow for easy manufacture/construction.

In a preferred example the clutch incorporates a back torque limiter, which reduces the effect of engine braking by allowing limited slip ofthe clutch when engine speed decreases during deceleration. It is desirable to reduce the effect of engine braking since it may adversely affect the handling characteristics of the motorcycle, particularly by causing the rear wheel of the motorcycle to lock. In a particular example, the clutch will be fabricated from carbon fibre and may, for example, be a clutch provided by AP Racing.

Pistons and connecting rods

The pistons are coupled to the crankshaft as illustrated in the schematic diagram of Figure 10 (not shown to scale) . The engine comprises a respective connecting rod for each cylinder, mechanically linking the pistons to the crankshaft and converting the linear motion of the pistons into rotational motion of the crankshaft in a known τπaΗner;1n^~a^~preferτed^"exΗmple ώ^"e connecting rodisfabricatedfromrforged titanium, which has low density and high-tensile strength. A material of low density is used in order to minimise the mass and inertia of the connecting rod, which enables high speed operation of the engine at speeds of 15,000 to 16,000 revolutions per minute.

To ensure that the force imparted to the piston by the expansion of gases in the cylinder is efficiently transferred to the crankshaft, it is necessary to eliminate or at least minimise lateral motion of the connecting rod, that is, motion in directions

"perpendicular to^"the^"axis of the^"cylinder. In^~an^~attempt to^'achieve this, the separation between the small end-of the onnecting roiand-me-piston-may-be-rm^imised, thus„ preventing the connecting rod from sliding along the gudgeon pin. The connecting rod and the piston may comprise, for example, titaniurn and aluminium respectively. The small end of the connecting rod is preferably coated to reduce the risk of bonding between, for example, the titanium and aluminium components. For example, the small end may be coated with a layer 1420 of molybdenum. In an alternative example, the small end ofthe connecting rod is coated with a layer of chromium nitride (CrN).

In a preferred example; the dimensions ofthe connecting rod"are^"as^~shσwn in Figures 11 A to 1 ID. In particular, the length of the connecting rod between the axes of the gudgeon pin and the crankpin is 94.5 millimetres, the width of the small end in the direction of the axis ofthe gudgeon pin is 16 millimetres, the radius ofthe small end is 16 millimetres, the thickness of the big end in the direction of the axis of the crankpin is 18.5 millimetres and the radius ofthe big end is 33.5 millimetres. Figure 1 IB also illustrates the region of the small end which is, for example, coated with chromium nitride.

The pistons are of forged aluminium and the shape of their undersides is shown in Figure 12A. The nine shaded areas highlight regions hr which the piston is indented in order to reduce the mass of each piston. The indented regions could be formed by machining, or may be cast as part ofthe shape ofthe piston. The inertia of each piston is minimised by reducing the mass of the piston in this manner, which assists high speed opeTatiϋfirof me^~ ngirø7^"R^"eτiπcin^"g^~m^"e^~weighrOf the ρistons^_also helps to minimise the total mass of the engine. The shape of these regions significantly reduces the mass of the piston without adversely affect the strength of the piston. A more detailed representation of the underside of the piston is shown in Figure 12B.

The design and dimensions of a preferred example of a piston is illustrated in Figures 13 A to 13G. The piston crown 3000 shown in Figure 13 A comprises five depressions. Three depressions 3002, 3004 and 3006 correspond to the positions of the inlet

^""valves, ^"while^"~the^~ fematning^_two^epressiras^~3008^" and^" 3010^* correspond to the positions ofthe exhaust-valves These-depressions-serve-to control thexombustion of fuel within the combustion chamber, in order to maximise power output from the engine. The side elevation of the piston crown 3000 shown in Figure 13B shows the locations of the piston ring groove 3012, the oil groove 3014 and the gudgeon pin hole 3016. Cross-sectional ofthe piston are shown in Figures 13C to 13E and Figure 13F shows another side elevation of the piston.

An alternative example of a piston is shown in Figures 14A and 14B. Another alternative example of a piston is shown in Figures 15A to 15C. Cooling system

The engine 20 is liquid cooled. The system is driven by a pump mounted on the engine casing 22. The pump pumps coolant, for example a water/antifreeze mixture, around a cooling circuit. The cooling system may be pressurised.

In general, the system is preferably configured such that the rate of flow of coolant is fastest past elements of the engine for which cooling is most critical (for example, the exhaust aperture and valves). The coolant itself is cooled by passing through a radiator, an example of which (and the mounting thereof) is discussed later.

Air intake

With reference now to Figures 16 and 17, the air intake ofthe motorcycle 10 is now — αx^crib^ifffurt er^ Oϊnchϊdes a front air -intake, generally-indicated by- reference numeral 2000, located forward of the steering head 2004, and below the front screen 2002. The air intake 2000 passes through a front fairing 2001 and opens into a flow passage 2006 which passes directly through the front head- stock and into an airbox 2008 (shown in Figure 17).

The air intake 2000 includes a mouth portion which tapers off as it extends into the flow passage 2006. The steering head 2004 passes through a column 2010 which ^" eΕtendsiongitudinally through thecentre of theflθw^"passage 2006. A transverse web 2011 extends across-me-flow_passage-2006_ancLarQuncL^

The airbox 2008 is provided with an air filter 2012 and is connected to the forward facing intake trumpets of the engine.

As mentioned, the air intake 2000 is located right at the front end of the motorcycle 10. Thus, when the motorcycle 10 is travelling at high speed, air is forced through the mouth of the air intake 2000 and into the airbox 2008.

The variable intake trumpet system will now be described with reference to Figures 18A and 18B. In these figures, the variable trumpet system, generally referred to by 1600, is shown installed on the engine 20.

In this particular example there are three trumpets: one for each cylinder of the engine. Each intake trumpet 1602 (shown here in its uppermost position) may be formed by a carbon fibre composite material comprising carbon fibres woven into shape and impregnated with resin. Each trumpet is formed around at least part ofthe throttle body 1603 of the engine. The body of each trumpet 1602 flares out at the upper extremity such that a lip 1604 is formed. The trumpets are variable in that their position may vary relative to the throttle body along-the axis 1614 (as shown-in Figure 18B). The trumpet position may vary continuously from the uppermost position at 1602 to the lowermost position at 1606, effectively varying the tuning of the engine.

- In Figure 18A, reference is made to the fuel injection system; the fuel injectors 1608 are shown in position above the valve trumpets 1602. Air is mixed with fuel from the fuel injectors 1608 in the region ofthe mouth ofthe intake trumpet 1602 before being passed to the cylinder where the fuel-air mix is ignited with a spark from a spark plug timed by the Engine Management System (described elsewhere). The fuel injectors are supported in place by the fuel rail 1610 which also distributes fuel to the fuel injectors. The fuel injectors are omitted from Figure 18B for the sake of clarity.

In a preferred example, the threeindiyiduaLtrumpets_1602.are mechanicaUy_c_Qupled_ together through the linkage 1612 in order that all the trumpets may be maintained at substantially the same position relative to each respective cylinder intake at any one time.

With particular reference to Figure 18B, the means for varying the position of the trumpets along the direction 1614 are now discussed. The mechanical linkage 1612 provides a means of simplifying the action of varying the position of the trumpet. In a preferred example, two guide rods 1616 are provided and the mechanical linkage 1612 is extended to couple with each guide rod 1616 at 1618. The two guide rods are diametrically opposed. In a preferred example, the coupling at 1618 provides a point of actuation for the variable trumpet system; that is, the linear position of the trumpets along the axis denoted by 1614 may be controlled by applying action to the coupling at 1618. The means for providing this action to the point 1618 are omitted for the sake of clarity. However, suitable hydraulic, pneumatic, electric, gear driven or cam assemblies may be provided to effect this action.

In one example such as that shown in Figure 18B, the control of the trumpets is effected through the rod 1620, shown at two positions 1620A and 1620Bv-The rod 1620 is connected through a gear assembly 1622 to the guide rod 1616 such that, when the rod 1620 is moved from 1620 A to 1620B and vice versa, the guide rod applies force to the coupling point 1618, and the trumpet positions are varied

-cam drive, rack and pinion, or any other suitable drive system-may be used.

Whereas in the present example, the fuel injectors are disposed to inject fuel axially with respect to the throttle body and in the vicinity of the mouth of the trumpets, in a further example, the injectors are mounted in a wall of the throttle body below the throttle butterfly valve.

ijCrtnτca ioϊr

The lubrication system, will now_be described with reference to Figure 19.

Oil is pumped from an oil sump 380 into the lubrication circuit inside the engine by- an oil pump 622 (for example a volumetric pump). The oil pump 622 comprises a drive shaft (not shown) carrying a gear which is driven by the clutch primary gear. Before entering the oil pump 622, oil from the sump 380 first passes through a strainer 382 to remove contaminants. Oil flows from the pump into a heat exchanger or radiator 604 mounted near the engine on the motorcycle, which reduces the oil temperature. After exiting the heat exchanger, oil passes through an oil filter 400 and into the lubrication circuit. Oil within the lubrication circuit may flow to the gearbox, the crankshaft, the cylinder block lubrication subcircuit 608 and/or the cylinder head lubrication subcircuit 606. The cylinder block lubrication subcircuit 608 lubricates components including the pistons 1412 and the balancing shaft 460 (described earlier). In a preferred example, oil jets are used to lubricate the pistons. The cylinder head lubrication subcircuit 606 lubricates components including the camshafts 240. Following the lubrication ofthe aforementioned engine components, oil is returned to the sump.

The oil feed to the crankshaft will now be described with reference to Figure 20.

An oil inlet conduit 6002 is connected through a magnetic oil seal 6004 to a nose 6006 of the crankshaft 440, specifically to a longitudinal bore 6020 extending from crankshaft nose 6006 through a section 6010 of the crankshaft into a main journal 601-2. A- diagonal bore 6024 extends from the -longitudinal bore 6020 in the main journal 6012 through a first crankweb 6030 into a first crankpin 6032 where it communicates with a crankpin bore 6022 which is open to the surface ofthe crankpin 6032. The diagonal bore 6024 continues into a second crankweb 6034, from where further bores (not shown) continue the oil circuit into the remainder ofthe crankshaft (including journal 6040) in a similar fashion. A portion ofthe engine casing is shown as 6050.

In use, oil is fed under pressure through the oil inlet conduit 6002 and the magnetic oil seal 6004 into the longitudinal bore 6020. The magnetic oil seal 6004 prevents oil from escaping from the interior of the engine, even at high crankshaft speeds.

The oil then flows under pressure into the diagonal bore 6024, which feeds the crankpin bore 6022 from where oil escapes onto the surface of crankpin 6032. The rotation of the crankpin 6032 with respect to the connecting rod (not shown here) ensures that the crankpin surface is sufficiently lubricated.

The diagonal bore 6024 also feeds further bores in the second crankweb 6034 and the remainder ofthe crankshaft (not shown further). In some examples, a further bore (not shown) is provided in each main journal, in the example of journal 6012 providing oil flow into a circumferential groove 6016 in the bearing 6014, thus lubricating the journal bearing. In other examples, oil is fed to the further journal bearings separately.

In a preferred example, the lubrication system also contains a pressure relief valve (not shown), through which oil may pass after exiting the oil pump. Excess oil pressure may occur due to thermal expansion or due to abnormally high pressure at the exit of the oil pump, which may be caused by a high pump speed wliich is in turn caused by high engine speed since the pump is mechanically driven. byLthe-engiheZ The pressure relief valve reduces pressure in the lubrication circuit to normal operating levels by allowing some oil to pass into the sump directly after leaving the praπpr^"

In a preferred example, an additional pathway is provided which allows oil to bypass the heat exchanger. This bypass pathway may be useful when oil is at a low temperature, such as shortly after the engine has started.

Gearbox The gearbox is a six-speed extractable gearbox, for example a racing gearbox of the type provided by ADM. In a preferred example, the gear ratios of the gearbox may be changed. A gearbox of the general type is described later.

In the engine shown in Figure 2, the gearbox is inserted into an aperture on the left side of the engine casing. A removable cover is provided for enclosing the engine.

Engine management system

The engine management system will now be described with reference to Figure 21.

Figure 21 shows an engine management system (EMS) 1200 comprising engine control unit (ECU) 1240, for example the MF4 ECU manufactured by Magneti Marelli. ECU 1240 receives inputs from a number of sensors. The main sensors comprise crankshaft sensor 1202, camshaft sensor 1204 and throttle sensor 1206. Auxiliary sensors include air temperature sensor 1208, air pressure sensor 1210, water temperature sensor 1212, fuel pressure sensor 1214 and universal exhaust gas oxygen (UEGO) sensor 1216. Each of these sensors is appropriately mounted on the engine 20 or in the exhaust pipe. ECU 1240 comprises a battery voltage sensor 1218.

Sensor readings may be recorded for later analysis using data recorder 1242. In preferred examples, data recorder 1242 comprises random access or flash memory. Communication with other systems (for example a personal computer or laptop) • occurs via I/O interface 1244. I/O interface 1244 may, for example, be used to configure the EMS, to modify the engine control maps, or to transfer recorded sensor readin^^roin clataTreϋoTder 1242r^~

Using the readings from the sensors, the ECU calculates ignition time (when to ignite), injection duration (how long to inject fuel for) and injection phase (injection end time), and uses the results to control ignition coils 1220 and fuel injectorsl222.

The crankshaft sensor 1202 comprises an inductive sensor triggered by teeth on a wheel (not shown) mounted on the crankshaft 440. In a preferred example, the crankshaft-mounted wheel has ten such teeth spaced 36 degrees apart, positioned such that the first tooth is aligned ..with the_sensor after the, crankshaft has rotated six degrees past top dead centre for the ignition cycle of the first cylinder. The crank signal provided by the crankshaft sensor therefore divides the crankshaft rotation into ten parts and the engine cycle (two crankshaft rotations) into twenty parts. From the crank signal the ECU calculates the engine speed (n).

The camshaft sensor 1204 comprises an inductive sensor triggered by a single tooth

(not shown) which is mounted on one of the camshafts 240a, 240b. The tooth is positioned such that it is aligned with the sensor when the crankshaft, and thus the camshaft, has rotated through 350 degrees after top dead centre for the ignition cycle of the first cylinder. Since the camshafts rotate only once per engine cycle, the ECU uses the signal from the camshaft sensor to identify the start of an engine cycle. With the start of the engine cycle known, the ECU then determines the position of the crankshaft, and hence the position within the engine cycle, from the crank signal.

The throttle sensor comprises a potentiometer connected to the throttle linkage. This gives the throttle opening as a voltage (for example between 0.5 V for a closed throttle and 3.5 V for a wide open throttle) from which the ECU calculates the throttle position

Using the engine speed and the throttle position, the ECU calculates three control parameters: injection duration, injection phase and ignition time. Since under normal conditions the injectors supply fuel at a constant rate, the amount of fuel injected is determined by the injection duration. The injection phase is the injection end time, that is to say the time at which injection should end. The injection start time can be determined by subtracting the desired injection duration from the injection phase.

The ECU calculates these control parameters using a number of engine control maps.

Specifically, the EMS comprises an injection phase map, an injection duration map and an ignition time map. These maps are provided in the form of two-dimensional

^~lbc .-up tablesln lexerd by^"thrOttle^"pO itiόn (α)^~arfd engine^'speed (n). Such systems are generally, referred to as α-n systems.

In a second step, the injection duration and ignition time parameters thus calculated are corrected based on the auxiliary sensor readings. To this end, correction maps are provided for each of the auxiliary sensors. From the correction maps, correction multipliers for the injection duration and correction offsets for the ignition time parameters are determined and applied to the respective parameters. In a particular example, a correction map is provided for the injection time in dependence upon the exhaust gas sensor 1216. For the air temperature, air pressure, and watertemperature- sensors, correction maps are provided for both injection time and ignition timing. Further correction factors for both injection time and ignition timing are calculated based upon atmospheric pressure, which is measured by the air pressure sensor when the engine is not running. There is an additional correction factor for injection time, based upon battery voltage sensor 1218 measurements.

For example, the water temperature correction map may in part define the firing up strategy for the engine by specifying an increase in the amount of fuel injected at low water temperatures, that is to say, when the engine is cold.

Final correction maps are associated with each of the three pylinderslto allow fo ^" small variances in air flow to the cylinders due to mechanical considerations such as positioning of the cylinders, arrangement of the intakes and so on.

The mapping data for the various engine control maps can be adjusted for different purposes, conditions and rider preferences. For example, one or more of the maps may be adapted to enable the injection of fuel during slowing/braking in order to alter engine braking characteristics. Furthermore, the maps may be optimised for particular requirements. For example, the maps may be adjusted to maximise fuel efficiency or to maximise engine performance, and may in particular be modified for different tracks/conditions.

Additional features ofthe engine management system include: assisting upwards gear shifts by cutting ignition and/or injection and reducing power; emergency fuel cut, in order to stop the engine for safety reasons; the ability to adjust the air/fuel mixture when the engine is idling; and Delta Engine speed (Delta Ne) controlling, in which the engine speed is smoothly varied during acceleration by reference to a series of correction maps, which are look-up tables containing optimum values for engine speed for a given current engine speed, change in engine speed and gear position.

Further sensors are provided as part of the engine management system-whieh-dø nøt- directly influence control of the engine. These include an oil pressure sensor, an oil temperature sensor, a gear position sensor and a rear wheel speed sensor. Readings from these sensors are stored by the data recorder for later analysis.

The engine management system also makes provision for varying the position ofthe intake trumpets in order to implement the variable intake system which is described elsewhere.

Additionally, provision is made for drive-by-wire (DBW) throttle control, in which engine torque is optimised by means of a feedback loop controlling throttle position as shown in Figure 22. The drive-by-wire subsystem takes inputs from the throttle position sensor 1206, the camshaft sensor 1204 (in the form of a value of engine speed), the rear wheel speed sensor and the gear position sensor, together with an

the optimum throttle-position -the ECU refers to a series of maps, which are provided in the form of two-dimensional look-up tables indexed by throttle position and engine speed. There is one map for each gear position. The throttle valve is adjusted by a hydraulic actuator to a position, determined from the map, that will give optimum engine torque for any given engine speed and gear selection.

In an alternative example, certain functions of the ECU may be provided by a ^~secOnc!ary^™e gine^^^^ throttle control, data logging, control of a.semi-automatic gear shift and control of variable trumpets.

The ECU and associated components of the engine management system can be positioned at a convenient location on the motorcycle, for example behind the dashboard, or can be attached to the outside of the engine, for example below the sump.

An alternative, second, example of an engine will-now-be described-with- reference to Figures 23 to 26. The engine of this example is also intended primarily for use in racing motorcycles, particularly those for use in Motorcycle Grand Prix.

Three external views ofthe present example are shown in Figures 23 A to 23C, which are respectively a left side elevation, a front elevation and a plan view.

This example is substantially similar to the previous preferred example described in respect of Figure 2, but with the following main differences:

• In contrast to the previous example, in which the cylinders were angled back from the vertical by 15°, the cylinders in the present example are angled"- vertically. As may be expected, the dimensions of engine components that were previously described differ from those of the present example.

• - In contrast to the previous example, which comprised three inlet valves per cylinder, the present example comprises two inlet valves per cylinder.

• In contrast to the previous example, in wliich the closure of the inlet and exhaust valves was achieved by means of a coil spring, the valves of the^" present example are closed using a pneumatic mechanism.

Since the present example uses just two inlet valves for each cylinder, in comparison to the threeinlet valves for each cylinder of the previous example, the area of each valve is made larger to ensure that an adequate volume of air/fuel mixture enters the combustion chamberin each inlet cycle. Increasing the area of each valve causes a corresponding increase in the mass, and thus the inertia, of each valve. To allow high speed operation of the engine, inlet valves are preferably closed using pneumatic valve springs which are capable of faster valve closure than coil springs.

— Figure 24A shows the valve spring-meehanism eønsisting-øf four-similar- pneumatic valve spring assemblies 1500 (that is, two inlet and two exhaust assemblies). The assemblies are disposed to each other at an angle determined by the placement of valves in the combustion chamber. Each pneumatic assembly 1500 comprises a hollow cylindrical body 1502, a hollow cylindrical cap 1504, a valve 1506 and a pushrod 1508. The internal diameter ofthe cap is greater than the external diameter of the body, allowing relative motion between the cap and body along the axis ofthe pneumatic assembly. The valve 1506 is attached to one end of a pushrod 1506 which is aligned along the axis of the pneumatic assembly. The other end of the pushrod terminates on the inside surface of the cap 1504.

Figure 24B shows a cross section, through the line A-A indicated in Figure

24A, of six of the twelve pneumatic valve spring assembles required for the

-Ihre^cylincleTm^ a cavity 1512

— which-is filled with a compressible gas. Thegas is contained within the cavity by seals 1514, 1516.

The assembly body 1502 is rigidly mounted between the inlet camshaft and the combustion chamber, such that the top surface ofthe cap 1510 is in contact with the cam lobes and the valve 1506 occludes the inlet aperture of the combustion chamber. During operation of the engine, rotation of the inlet

upon the cap

1504. The uneven profile of the cam lobes causes the force exerted upon the cap to vary during the combustion cycle.

During the intake cycle, the cap is depressed by the cam lobe which causes motion of the valve, which is rigidly connected to the cap via the pushrod. Thus, the valve moves into the combustion chamber, allowing the influx of air/fuel mixture through the inlet aperture. Additionally, depression ofthe cap by the pushrod causes compression of the gas contained within the cavity 1512τ During the latter half of e ntake-eycle,- e-profile-of-me-eain4obe causes the force exerted upon the cap by the cam lobe to decrease. As the force from the cam lobe decreases, expansion ofthe gas within the cavity 1512 causes the cap to move upwards (towards the camshaft), which in turn causes motion of the valve and the closure of the inlet aperture.

Note that closure of the exhaust valves may in a further example be achieved using a coil spring arrangement as in the previous example, or using further pneumatic valve spring assemblies as described.

In the present example, the cross-sections of the intake trumpets are more circular than for the previous example.

The present example has a cooling system as described in the following paragraphs.

With reference now to Figure 25 of the drawings, particular aspects of a cooling arrangement for an engine cylinder head and combustion chamber are now described in further detail. The combustion chamber 2100 ofthe engine shown in Figure 25 is defined between the upper surface 2112 of a piston head^" 2114 and the lower surfaces of each of a pair of intake 2116 and exhaust 2118 valves respectively. In Figure 25 the combustion chamber 2100 is shown with

^~fh^"e pϊsfόTrin^"the^~top^"cead cehtfe^"(TDC) ^"or highesrpbsition, just prior to ignition by a sparking plug (not shown).. .

The piston head 2114 has a plurality of pistonrings 2111, and is connected via a connecting rod (described elsewhere) to a crank shaft (described elsewhere) such that it can reciprocate in a cylinder 2120. The cylinder 2120 is sealed via a gasket (not shown) to a cylinder head, generally indicated by reference numeral 2122. The cylinder head 2122 is provided with a plurality of intake and exhaust ports. In the drawing a single intake port 2124 and a single exhaust port 2126 are shown. The cylinder head 2122 also includes valve guides 2128, 2130 for guiding displacement of push rods 2132, 2134 connected to the valves 2116, 2118. The cylinder head 2120 also includes circumferential valve seats 2136, 2138 provided at respective combustion chamber ends of each of the intake 2124 and exhaust 2126 ports.

During combustion, the cylinder 2120 and the entire cylinder head 2122 are subject to tremendous heat. Hence the cylinder 2120, cylinder head 2122 and associated intake 2124 and exhaust 2126 ports, valve guides 2128, 2130 and valve seats 2136, 2138 all require cooling. Thus, a web of cooling ducts are provided, which feed liquid coolant around the cylinder 2120 and in and around the various components mounted within the cylinder head 2122.

- -The web ofcooling-ducts are all interconnected and-thus, flow rate through these ducts is interrelated. Thus, for example, flow rates are higher through ducts having a relatively smaller cross-sectional flow path than flow rates through ducts having a relatively larger cross-sectional flow path.

In particular, the cylinder head 2122 includes a first set of ducts 2140, having a relatively smaller- cross-sectional flow path, which allows liquid coolant to

^""flow at a relativeljThigh ra e adjacenrthe^'valve ^"seats 2136, 2138. The valve seats are subject to tremendous heating andthe small cross-sectional flow.path of these cooling ducts 2140 causes a high flow rate of liquid coolant through these ducts thereby facilitating faster cooling of the valve seats 2136, 2138, and surrounding area.

A second set of cooling ducts 2142 are provided above the first set of cooling ducts 2140 in the cylinder head 2122. This second set or "deck" of cooling ducts 2142 have a relatively larger cross-sectional flow path than the first set of cooling ducts 2140 ^~Heating in this area of he cylinder head- ire; adjacent— the valve guides 2128, 2130, is not as significant as in the lower portion ofthe cylinder head 2122. Thus, the flow rate of liquid coolant in the second set of cooling ducts 2142 may be lower than in the fist set of cooling ducts 2140.

The cylinder 2120 itself is also provided with a set of cooling ducts 2144 which cool down the top of the cylinder adj acent the piston head 2114. These cooling ducts 2144 also have relatively small cross-sectional flow paths.

In an alternative arrangement, the cooling ducts 2140,2142 in the cylinder head 2122 may be independent from the cooling ducts 2144 provided in the cylinder 2120 itself.

In contrast to the previous example, in which lateral motion ofthe connecting ^"Tϋd^"was reduced by enlarging the small end ofthe connecting rod, and further coating the short end, lateral motion of the connecting rod in the present example is reduced by enlarging the big end of the connecting rod. The width ofthe big end in the direction ofthe axis ofthe crankpin is comparable to the separation between the crankwebs, such that the big end makes contact with both adjacent crankwebs.

To reduce the risk of bonding between the big end and the crankwebs, the big end ^"of ^"the ^"connecting^" rod may^""be^~coafed^'"with a layer of, for example, molybdenum or chromiuπLnitride.

• The connecting rods in the present example have a greater length than in the previous example. The length of the connecting rods between the axes of the gudgeon pin and the crankpin of the present example is 118.84 millimetres, in contrast to 94.50 millimetres for the previous example. Other dimensions ofthe connecting rods ofthe present example are as indicated in Figures 26 A to 26D.

A further, third, example of an engine is now described with reference to Figures 27 to 47; features corresponding with features of the preceding examples are generally denoted using the same reference numbers.

Figure 27 shows motorcycle 10, emphasising the location and attitude ofthe engine 20. The engine 20 is mounted in a chassis 12, upon which is also mounted fairing components and a seat and so on, as is customary. At the front ofthe chassis, there is a headstock 13, to which is mounted the triple tree carrying the front forks and wheel. The swing arm carrying the rear wheel is mounted to the rear of the chassis as described further below.

In particularly preferred examples, the engine is for use in production or road motorcycles, including motorcycles suitable for Superbike competitions such as the World Superbike competition.

Various features relating to the third engine, such as the orientation ofthe engine and cylinder head configuration; crankshaft and balancing shaft; cooling system; valve train; air intake; gearbox; engine tuning; engine management system; compactness of the engine, and weight transfer will be described, following an overview of the engine.

Engine^~Overview^~~

Five external views of a preferred example are shown in Figures 28A to 28E, which are respectively a right side elevation, a left side elevation, a front elevation, a rear elevation and a plan view of the engine. The same example is also shown in perspective views 29A to 29C.

In overview, the engine is a four-stroke engine 20 comprising three cylinders 80a, 80b, 80c in an in-line configuration, each having a bore and stroke of 88mm and 49.3mm respectively. This oversquare shape may enable the engine to be run at higher speeds. In an example intended primarily for road use, the combustion chamber of each cylinder (defined by the shape of the cylinder head and the piston crown, and preferably substantially hemispherical) has a size giving rise to a compression ratio of 12 : 1 to 13 : 1 or higher. In a further example intended for racing, for example in the World Superbikes Competition, the compression ratio is 13:1 to 14:1 or higher.

As may be seen from Figures 28 and 29 the engine is housed in an engine casing 22 which comprises a cylinder head cover 40 detachably located on a cylinder head 60. The cylinder head 60 comprises three inlet apertures 70a, 70b 70c which are disposed (in contrast to known production and road motorcycles) on its forward side 62. Attached to the inlet apertures 70 (in an elastic manner, in a preferred example) are respective throttle bodies 100a, 100b, 100c having respective intake trumpets 120a, 120bf42Ucr-^"EΕrctrτnt^ 120 ^"feeds a respective cylinder 80 as further described below. In the rear side 64 ofthe cylinder head 60 are disposed three exhaust apertures 200a, 200b, 200c to which are attached respective exhaust passages (not shown). The exhaust apertures 200 are fed by the combustion chambers 82 via two exhaust ports (not shown) per cylinder as further described below.

Having the inlet apertures on the forward side of the engine and the exhaust apertures to the^'rear may allow ^"the exhaust system^~and^" the intake system to be disposed at a distance from one^another which_may_ove_rcome or alleviate the problem in known engines in which the intake air is heated by the exhaust gases due to the proximity of the systems to one another. In addition, the exhaust system is remote from the coolant and lubricant radiators (described below) which may result in less heat transfer from the exhaust system to the radiators. As a further result, the engine may be located further forward than in known motorcycles allowing for more flexibility in the location of the centre of gravity.

The cylinder head 60 houses two camshafts 240a, 240b driving two inlet and two exhaust valves per cylinder. The valve train is described in further detail below. The cylinders are each lined by a respective removeable cylinder liner. The use of separate liners may reduce the likelihood of distortion, and such liners may be manufactured, removed and replaced independently of one another and ofthe cylinder head/engine block and may provide a more reliable solution. Furthermore, the liners may be removed and the engine block reused.

Mounted on the right side ofthe cylinder block 24 is a water pump 300 for pumping coolant around the engine. The cooling system is also described in further detail below.

The engine casing 22 comprises a removable crankshaft casing 320, a removable clutch casing 340 and an aperture for a removable sealed gearbox magazine 420.

An oil pump is mounted within a portion 360 of the engine casing. The oil pump draws oil from a sump 380. An oil filter 400 is provided. The lubrication is also further described below.

Orientation of engine and cylinder head configuration

As indicated above, the engine comprises three cylinders 80 in an in-line configuration. The cylinders are angled back from the vertical by 15°. In further examples this angle is between 13.5° and 16.5°, and in still further examples, it is between 12° and 18°. In yet further examplesJhe angle is up_tQ_20° or 25°. As a. result, the inlet trumpets 120 point upwards to a greater degree. The relative positions of the other features of the engine in a particularly preferred example are described below with reference to Figure 30.

Figure 30 shows the cylinder head 60 of an example. The example shown comprises two injectors 502, 504 (for example, standard injectors provided by Magnetti Marelli) per cylinder 80; the first (or top) injector 502 is disposed axially witfrrespect to the throttle body 100 and trumpet 120 upstream of the throttle butterfly 102, and the second (or bottom) injector 504 is disposed in a wall of the throttle body 100 downstream of the butterfly 102 and angled such that it directs fuel in a generally downstream direction. Each ofthe six injectors is fed by a fuel rail 506, for example as also provided by Magnetti Marelli. Further examples (for example, motorcycles intended primarily for road use) comprise a single injector (below the butterfly) per cylinder.

The axis of the trumpet and the throttle body is disposed at an angle of 49° from the_ axis ofthe respective cylinder. Disposed between those axes, at an angle of 9^° from the axis of the cylinder, is the inlet valve (for example, a standard inlet valve as provided by Dell West - a particularly preferred example further uses ^"valve plates made by Dell West and/or valve springs - preferably coil valve springs - made by Kurt Kauffmann GmbH). In a particularly preferred example, intended for racing, the ^"~vπlves^~are^~fϋrnτeτl^~1roτ-^^^ The^~twσ^"inlervalve^"s for each^" cylinder are in a

-parallel configuration.

On the exhaust side of the cylinder head, the axis of the exhaust valve is disposed at an angle of 12° to the axis ofthe cylinder. The axis of the cylinder is disposed at 61^° from the axis of the exhaust port. The two exhaust valves for each cylinder are in a parallel configuration.

^~In^~~a^"preferred example ^"the valve ^"guides^~for each^" of ^~e ^"valves ^"are formed of a manganese-copper alloy and/or the valve seats are formed, of a copper-ber llium alloy.

Other dimensions of this specific example, which is asymmetric, are shown in Figure 30: for example, the radial distances ofthe axes ofthe inlet and outlet camshafts from the axis ofthe cylinder (31.8mm and 45.4mm respectively), the distances parallel to the axis of the cylinder of the centre of the inlet apertures and the outlet apertures from the lowest point ofthe closed valves 86, 90 (73.42mm and 48mm respectively), the radial distances between the gudgeon pin (when the-piston-is-at-top dead centre) and the axes of the inlet and exhaust valves 86, 90 (9.83mm and 15.72mm respectively).

In certain preferred examples, such as motorcycles intended for use in races such as those of the superbikes tournaments, the gudgeon pins have zero offset. In other preferred examples, such as motorcycles intended primarily for road use, the gudgeon pins have a non-zero offset.

Note that preferred examples (such as that shown) comprise two inlet and two exhaust valves per cylinder, and that in the discussion of the position of the valves above, references to the axes of the valves shall be taken to mean a projection of the axes normally onto the plane defined, for example, by the axes of the respective cylinder and the respective throttle body.

The valves 86, 90 are driven via tappets by dual overhead camshafts 240a, 240b which are themselves driven by gears from the crankshaft 440 as described below.

The faces of the valves 86, 90, a portion of the cylinder head, the piston crown and the cylinder sleeve together cefine a generally combustion chamber which communicates with the inlet and exhaust ports via the respective valves, when opened. In a preferred example, the combustion chamber is generally hemispherical. In furtheTexamples, e cc^~>mbus form of a part of a cylinder. In a particularly preferredexample,ihe spark.plug.is disposed centrally with regard to the roof of the combustion chamber.

Figures 31A and 3 IB show further views of a cylinder head in accordance with an example. In each of the examples shown, the cylinder head has been designed with the compactness of the engine in mind. In particular, the angle between valves and intake ports is optimised to reduce the size of the cylinder head. This is in contrast to known systems in which this angle is made as small as possible in order to limit reduction in flow rate. Similar considerations have been- made-in- designing-the- exhaust port/valve angle. As is known, the base diameter of cams on the cam shaft determines the size of the tappets and so on. In the examples shown, the base circle has been defined to be large enough just to allow sufficient cam radius to give acceptable wear ofthe cam profile.

5 Figure 32 shows (in Figure 32A) a cylinder head 60 of an example showing in addition the location and the shape of the inlet apertures 70 (Figure 32B) and the exhaust apertures 200 (Figure 32C).

Figure 33 shows the profile of inlet passages 72 in a cylinder head of an example. 0 The passage shown begins at the butterfly 102 of the throttle body^"ΪOO^~"(fowards^~the^~" top ofthe figure) and descends to the inlet port 84 (towards the bottom ofthe figure).

As may be seen in the figure, in this example, the axis of rotation ofthe butterfly 102 ^" r t-a irs πc^ )f ^5^"mπrfrom the^~inlet ports- 84; land the throttle^" body 100 at the butterfly 102 has a cross-sectional area of 2370mm². The inlet apertures 100 in the 5 front face 62 of the cylinder head 60 are 108mm from the inlet ports 84, and have a width of 52mm, a height of 33mm and a cross-sectional area of 1479mm².

Downstream of the inlet aperture 70 each inlet passage 72 separates into two subpassages 73a, 73b, each of which feeds one ofthe combustion chambers X2 via a respective inlet valve 86. Between distances of 54mm and 34mm from their 0 respective inlet valve, the subpassages have a substantial uniform shape and cross-

^{" ""}sectiόhΕlafea of 1315mm².^"

throttie bodies 100 and the inlet apertures 70 are marginally closer together (98mm) than Λe axes c-f the cylinders (101.5mm).

5 In a particularly preferred example, various dimensions/angles of the cylinder head and associated features are precisely as marked in the figure and/or as described herein. However, in further examples, some or all of the dimensions/angles differ from those shown/described by plus or minus 25%, plus or minus 20%, plus or minus 15%, plus or minus 10%, plus or minus 5% or plus or minus 2%. 0 Crankshaft and balancing shaft

The engine 20 further comprises a crankshaft 440 (see Figures 35, 36 and 37A to C). The engine has an even firing order and the three crank pins 448a, b, c on the crankshaft 440 are equally spaced such that forces due to acceleration of reciprocating components are largely balanced in a known manner, either by each other or by extended webs 442 (which in a preferred example comprise heavy metal inserts) on the crankshaft. However, the outside two cylinders 80a, 80c produce an additional torque on the crankshaft which is not cancelled by the reciprocating masses of the pistons and so on or by the rotating masses of the extended webs 442.

To counter this torque, the engine 20 comprises a balancing shaft 460. The balancing shaft is driven by engagement of a gear 464 on the balancing shaft 460 and a gear 444 on the crankshaft 440. The balancing shaft driving gears 444, 464 have the same size

-such that-the balancing-shaft-4-60 rotates at the-same speed as the crankshaft 440.

The balancing shaft comprises two balancing masses: the first mass 466 is adjacent the gear 464, and the second mass 468 (which may contain inserts 470 of denser material) is adjacent the end of the balancing shaft remote from the gear^~ 64.^~ In a particularly preferred example in which the balancing shaft is used to drive the gearbox input shaft via the clutch, the second mass 468 is adjacent a balancing shaft

^■primary^~ge^"ar 472 on^~fe^"~baTan^"cing sh^"af "The^""bal^"anclng shaft primary gear 472 is arranged mesh with_a_clutch_primary. geArL_(.as_de.s.cribed_belQw with reference to Figure 38).

As can be seen (for example, in Figure 37B), the first and second masses 466, 468 are disposed on opposing sides ofthe balancing shaft 460. In addition to the effect of the first and second masses 466, 468, rotation ofthe balancing shaft 460 may additionally produce a torque as a result of one or more cavities or bores 474 in the gear 464 (or indeed in the further gear 472, although such cavities or bores are not shown).

In a preferred example, the webs on the crankshaft have a mass designed to balance the centrifugal forces on the crankshaft to an extent of 50%. This may allow for the use of a small, light crankshaft which is cheap to produce and which has low inertia. In preferred refinements of this example, the crankshaft has at least two non- symmetric crankshafts. In a further preferred example, the webs have a mass such that they balance 100% of the centrifugal forces.

In a particularly preferred example (such as that shown in the Figures), the balancing shaft 460 is located above the sump, in contrast to known system using a balancing shaft in which the shaft is located forward ofthe crankshaft and in which the oil pump is located-above the sump. -Such a configuration-may-give rise to a shorter engine length and to the ability to use the balancing shaft as part of the power train as described elsewhere.

In a particularly preferred example, the balancing-shaft-mounted balancing shaft driving gear 464 has a radius greater than that of the further gear 472. Additionally, the radius of the second mass 468 is greater than the radius of the further gear 472

(and in particular, the radius of the second mass 468 is greater than the radius of the dedendum circle ofthe balancing shaft primary gear 472). This may be ach eved^'fδF example by forming the balancing shaft 460 as an assembly. A balancing shaft formed in one piece may be produced more cheaply than a balancing shaft assembly, and ^"it ^"may be^"more stable than a shaft a^"s^"sembl^"ed^~from a number ""όf pairts^".

As mentioned above, the balancing shaft primary gear 472 on the balancing shaft 460 engages with the clutch primary gear 482. For this reason and since in the preferred example the gearbox 420 is rearward of the crankshaft 440, the balancing shaft 460 is to the rear, and slightly lower than, the crankshaft 440. The engine casing 22 has a single split (not shown) at approximately the level of the shafts to allow for easy manufacture/construction.

Figure 38 is a schematic diagram of the power train beginning at the engine 20. The cylinders 80 turn the crankshaft 440, which in turn drives the balancing shaft via meshing gears 444, 464. The balancing shaft drives the primary drive which comprises the balancing shaft primary 472 and the clutch primary 482. This arrangement means that, in order for the sprocket 422 to turn in the correct sense, the crankshaft must turn in the opposite sense to the rotation of the wheels of the motorcycle, in contrast to known motorcycles in which the crankshaft and the gearbox output shaft rotate in the same sense. Such an arrangement may confer the advantage that the rotation ofthe crankshaft against its inertia serves to increase the downward force on the front wheel of the motorcycle (rather than reducing it as in known motorcycles) resulting in an ability to accelerate a faster rate before the front tyre of the motorcycle leaves the ground. In a particularly preferred example having a weight distribution of approximately 50% on each wheel, the effect is such that an effective mass of approximately 1.5kg is added to the load on the front wheel, which

-increase- in the acceleration, possible before-the front wheel leaves-the ground.

Cooling system

As indicated above, the engine 20 is liquid cooled. The cooling system in an example is represented schematically in Figure 39. The system is driven^~by a purhrT300 (preferably a radial flow pump) mounted on the engine casing 22. The pump 300 pumps coolant (which in a preferred example is a water/antifreeze mixture) around ^"~π όliffg c^" cuit:^"In^ passes coolant inside a water jackeLdisposedaround the engine, the system targets the flow of coolant to areas of the engine which require cooling. Hence, the cooling circuit comprises three subcircuits 314a, 314b, 314c, each of which cools a respective cylinder 80. The subcircuits 314 comprise two main branches: a first to provide coolant to the inlet and exhaust apertures and valves, and a second to provide coolant to the cylinder block 24. The flow rate and/or pressure of coolant in the second branch is restricted by a restrictor 312.

An alternative example is represented schematically in Figure 40. In this example, the cooling circuit is also separated into three subcircuits, which are further separated into two branches. However, in this example, a first branch serves to cool the cylinder block 24 and the exhaust apertures and valves, and a second branch, in which flow is restricted by a restrictor 312, provides coolant to the cylinder block and the inlet apertures and valves.

In general, the systems are configured such that the rate of flow of coolant is fastest past elements of the engine for which cooling is most critical (for example, the exhaust aperture and valves).

Figures 41 A to 41G show a number of views of the -coolant radiator of an-example.

The location ofthe radiator on the motorcycle may be seen in Figures 42 A and 42B.

As shown in the Figures, the radiator is mounted in front of the engine, and it is formed such that it is concave forwards so that it traps air and funnels it past the

— adiator.- A-radiator inlet 306is-fed with hot coolant, via conduit 305 which passes under the airbox 130, by an engine coolant outlet 304 which is positioned adj acent the highest point of the engine to receive coolant, such that air bubbles exit the portion of the cooling circuit within the engine itself and pass into the conduit 305. The coolant passes through the radiator 310 and out via radiator outlet 308, via cohduif 303 to the cooling pump inlet 302. The coolant conduits 303, 305 pass directly between the front face of the engine and the rear of the radiator with the minimum o ible contWsiϋnT

In a particularly preferred example, the coolant conduits 303, 305 are the only external conduits in the cooling system, all other conduits being integral to (for example, by being cast in) the engine block/cylinder head/radiator.

In a further particularly preferred example, the cooling system contains less than one litre of coolant. In other examples, the system may contain less than 1.1 litres, 1.2 litres or 1.5 litres. The valve train

As indicated above, the valves are driven by gears from the crankshaft 440. The valve train is represented schematically in Figure 43.

5 The crankshaft 440 carries a valve train driving gear 446, which meshes with a large gear 286 on a compound idler shaft 282. The compound idler shaft 282 also carries a small gear 284, which meshes with a head idler gear 260 mounted on a head idler- shaft 262. The head idler gear 260 also meshes with gears 242a, 242b on the camshafts 240a, 240b. The valve train operates such that rotation of the crankshaft 0 440 in a first direction causes rotation of both camshafts 240 in the opposed direction. The camshafts 240 carry cams which drive the valves 86, 90 via respective tappets 292, in a known way.

-In~ a preferred example,- the-position ..of the compound-idler shaft 282 is adjustable 5 whereby the free play in the gears ofthe above-described valve train may be adjusted.

Air intake

As may be seen from Figures 28 and 29, the intake trumpets 120a, l2Ob7120c andlhe^" throttle bodies 100a, 100b, 100c are situated to the fore ofthe engine 20. The intake trumpets 120a, 120b, 120c are fed directly by an airbox (not shown). Given the short ^•~~~tttsTaTϊcτe^~'^^ motorcycle^"and the intake trumpets 120, the airbox and the. passage for

is of simplified construction as described below.

Figures 44A and 44B show perspective views of the chassis 12 of a motorcycle 10 into which the engine 20 is to be mounted. An air intake 14 extends from the front of the chassis 12 to the headstock 13. A passage is formed in the headstock 13 via which air from the intake 14 passes to an airbox 130. The cross section o the airbox 130 expands downstream ofthe headstock 13 in order to slow the air drawn into the airbox 130. The airbox is provided with-an-air^lter which is not shown-explieitly-, although its position 16 is marked in Figure 44B. Providing air directly to the airbox 130 in this way may allow for a more targeted flow of air into the airbox without a drop in pressure. In addition, less material is used in such a construction which provides for cheaper and simpler manufacture, and for a lighter construction in which it is easier to locate the centre of gravity where desired.

The intake trumpets 120a, b and c mounted to the cylinder head 60 of the engine 20 sit in an aperture 17 (see Figure 45) in the airbox 130. A seal (not shown) prevents- air from exiting the airbox 130 via the aperture 17 except through one ofthe trumpets 120.

Gearbox

As indicated above, the gearbox (preferably a six-speed gearbox) is an extractable mΗg^"a_iπeτ^" lτe^~g^"e^"a^ _an input shaft484 (or mainshaft) and an outputshaft 485 (or countershaft). A portion 484a of the input shaft is adapted to receive a clutch (not shown), for example as manufactured by Suter Racing Technology, for driving the input shaft.

The gearbox comprises a pair of gears for each speed of the transmissionTone of each- pair being mounted on the input shaft and the other on the output shaft, the pairs being in a constant mesh arrangement. The gears 1310, 1315 corresponding to first gear are ^" closest to the clutch mounting portion end of the gearbox 420; moving from that end ofthe gearbox (the right side of Figure 46), the gears for the particular speeds of the gearbox are found in the following order: first, sixth, fourth, third, fifth, second.

The input shaft mounted gears 1310, 1320, 1330, 1340 relating to first, second, third and fourth gears are interference fitted to the input shaft 484 such that rotation of those gears causes rotation of the input shaft. The remaining input shaft mounted gears are allowed to freewheel on the input shaft.

The output shaft mounted gears 1355, 1365 relating to fifth and sixth gears are interference fitted to the output shaft 485. The remaining output shaft mounted gears are allowed to freewheel on the output shaft.

The output shaft mounted sixth gear 1365 is a sliding gear splined to the output shaft such that it may be slid in a known manner (for example using a cam plate gear selector or, in a particularly preferred embodient, a drum gear selector arrangement) towards the clutch end of the output shaft (that is, away from the sprocket). Engagement dogs 1366 on the sliding gear engage with the Output shaft mounted first^" gear 1315 such that rotation of the output shaft mounted first gear causes rotation of the output shaft (that is, first gear is engaged).

Similarly, second gear is engaged by sliding the output shaft mounted fifth gear towards the output shaft mounted second gear; third gear is engaged by sliding the output shaft mounted fifth gear towards the output shaft mounted third gear; fourth gear is -engaged by sliding the output shaft-mounted sixth gear towards the output shaft mounted fourth gear; fifth gear is engaged by sliding an input shaft mounted fourth/fifth gear assembly towards the input shaft mounted fifth gear; and sixth gear is engaged by sliding the input shaft mounted fourth/fifth gear assembly towards the input shaft mounted sixth gear. In each case, engagement dogs^for example^~those having reference numbers 1356, 1366) on the sliding gear/assembly engage with the gear to be selected.

Engine tuning

In a particularly preferred example, the engine is tuned to provide a torque peak of 90 to lOONm at a speed of 10000 to 11000 rpm (preferably at 10500 rpm).

The intake ports 100 are formed to minimise pressure loss and to provide air flow of approximately 100ms^"1 when the engine is running at the speed giving maximum power.

The intake ports fit together. The position of the-throttle butterfly in each port-maybe adjusted independently, however when the engine is running, the throttle butterflies are actuated by a single mechanism (preferably a cable attached to a wheel mounted on one of the ports).

Engine management system The engine management system of the present example will now be described with reference to Figure 47.

Engine management system (EMS) 1200 comprises engine control unit (ECU) 1240.

ECU 1240 receives inputs from a number of sensors. The main sensors comprise crankshaft sensor 1202, camshaft sensor 1204 and throttle sensor 1206. Auxiliary sensors include air temperature sensor 1208, air pressure sensor 1210, water temperature sensor 1212, fuel pressure sensor 1214, and oil temperature sensor 1216.

^~~~l- ϋlruf ^"e^"seπ_^n r^^ engine^""2θ. ECU 1240

—comprise&a battery voltage sensor 1218.

Sensor readings may be recorded for later analysis using data recorder 1242. In preferred examples, data recorder 1242 comprises random access or flash memory. Communication with other systems (for example a personal computer or laptop)^"" occurs via I/O interface 1244. I/O interface 1244 may, for example, be used to configure the EMS, to modify the engine control maps, or to transfer recorded sensor nre^"ading from^~data^"re^"cϋrd^"erl2427

Using the readings from the sensors, the ECU calculates ignition time (when to ignite), injection duration (how long to inject fuel for) and injection phase (injection end time), and uses the results to control ignition coils 1220 and fuel injectors 1222.

The crankshaft sensor 1202 comprises a Hall-effect sensor triggered by teeth on a wheel (not shown) mounted on the crankshaft 440. In a preferred example, the crankshaft-mounted wheel has six such teeth spaced 60 degrees apart, at positions corresponding to top dead centre and bottom dead centre of eaeh of the three-pistons_^ The crank signal provided by the crankshaft sensor therefore divides the crankshaft rotation into six parts and the engine cycle (two crankshaft rotations) into twelve parts. From the crank signal the ECU calculates the engine speed (n).

One ofthe camshafts 240a, 240b comprises a single tooth (not shown) which triggers the camshaft sensor. Since the camshafts rotate only once per engine cycle, the ECU uses the signal from the camshaft sensor to identify the start of an engine cycle. With the start of the engine cycle known, the ECU then determines the position of the crankshaft, and hence the position within the engine cycle, from the crank signal.

The throttle sensor comprises a potentiometer connected to the throttle linkage. This gives the throttle opening as a voltage (for example between 0.5 V for a closed throttle and 3.5 V for a wide open throttle) from which the ECU calculates the throttle position

Using the engine speed and the throttle position, the ECU calculates three control parameters: injection duration, injection phase and ignition time. Since under normal conditions the injectors supply fuel at a constant rate, the amount of fuel injected is determined by the injection duration. The injection phase is the injection end time, that is to say the time at which injection should end. The injection start time can be determined by subtracting the desired injection duration from the injection phase.

The-ECUcalculates these control parameters using a number of engine control maps.

Specifically, the EMS comprises an injection phase map, an injection duration map and an ignition time map. These maps are provided in the form of two-dimensional look-up tables indexed by throttle position ( ) and engine speed (n). Such systems are generally referred to as α-n systems.

In a second step, the injection duration and ignition time parameters thus calculated are corrected based on the auxiliary sensor readings. To this end, correction maps are provided for each of e"^uxiliary"sensors. Fromihe-correctiOn maps~correctrøn- multipliers for the injection duration and correction offsets for the ignition time parameters are determined and applied to the respective parameters. For the fuel pressure sensor, a correction map is provided for the ignition time only. For the air temperature, air pressure, water temperature and oil temperature sensors, correction maps are provided for both injection duration and ignition time.

For example, the water temperature correction map may in part define the firing up strategy for the engine by specifying an increase in the amount of fuel injected at low water temperatures, that is to say, when the engine is cold.

The ECU also calculates the rate of change of the engine-speed and the rate of change^" ofthe throttle position. Further correction maps are provided to correct the injection duration and ignition time based on these parameters.

-Final-correction maps are associated with each of the three cylinders to allow for small variances in air flow to the cylinders due to mechanical considerations such as positioning of the cylinders, arrangement of the intakes and so on.

In examples where two injectors are provided per cylinder, an injector distribution map indexed by throttle position ( ) and engine speed (n) is provided which defines the distribution of fuel for injection between the upper and lower injector banks. This distribution is defined as the percentage ofthe total fuel to be injected which is to be injected by the upper (or lower) injector. The ECU adjusts the injector durations for the upper and lower injectors according to this distribution.

Typically, the distribution map will define a distribution whereby the upper injector provides most or all of the fuel injection for open throttle positions, for example, between 50% open and wide open throttle. This can have the effect of cooling the intake which in turn can increase fuel density. At less open throttle positions, for example, below 50% open, the lower injector is typically used predominantly or exclusively to avoid fuel condensation in the intake-above me-throttle-butterfty7- The mapping data for the various engine control maps can be adjusted for different purposes, conditions and rider preferences. For example, one or more of the maps may be adapted to enable the injection of fuel during slowing/braking in order to alter engine braking characteristics. Furthermore, the maps may be optimised for particular requirements. For example, in a road motorcycle, the maps may be adjusted to maximise fuel efficiency, whilst in a racing application, the maps may typically be designed to maximise engine perfomance, and may in particular be modified for different tracks/conditions.

Further sensors are provided as part-of the engine-management system which-db not directly influence control of the engine. These include an oil pressure sensor, a gear position sensor, and a UEGO (Universal Exhaust Gas Oxygen) sensor or lambda sensor for measuring the air fuel ratio in the exhaust. Readings from these sensors are stored by the data recorder for later analysis.

The ECU and associated components of the engine management system can be positioned at a convenient location on the motorcycle, for example behind the dashboard, or can be attached to the outside of the engine, for example^" belόwTHe^" sump.

Compactness of engine

It is desirable for the engine to be compact. The effects of a compact engine include greater ease in the positioning of the centre of gravity of the engine and hence the motorcycle, a lighter engine and hence a lighter motorcycle, greater control over mass transfer in dynamic conditions, and so on. A number of the above-described features give rise to such compactness, either independently or in combination with other features. These features include:

• The incline of the cylinders towards the rear of the motorcycle

• The position of the inlet apertures at the front of the engine and the outlet apertures at the rear

• The valve angles • The angles of inclination of the inlet ports and the exhaust headers with respect to the cylinder head

• The location of the balancing shaft above the sump rather than forward of the crankshaft • Gearing between the crankshaft and the gearbox input shaft allowing the use of a smaller clutch primary gear (the balancing shaft primary gear is not required to be no smaller than the webs of the crankshaft, whereas a primary gear on the crankshaft would be so restricted)

• The use of an end driven clutch • Short connecting rods (having a length of approximately twice the stroke of the engine): for example in an example intended for road use, connecting rods having a length of 99mm, and in an example intended for racing, for example in the World Superbikes Competition, connecting rods having a length of

--102.5mm • The orientation of the gearbox such that one shaft is above the other

A particularly preferred example comprises any one of, or any combination of any number of, these features.

Weight transfer

It Fdesirable^'under acceleration tθ^"have^~a^"transferof weighrtowards the rear, of the motorcycle. A number-of the above-described features-give rise-to such-a-transfer,- either independently or in combination with other features. These features include:

• The incline of the cylinders towards the rear of the motorcycle • The features giving rise to compactness of the engine, which enable the engine to be mounted relatively high up in the chassis.

In a particularly preferred example, ballast may also be used to adjust the overall mass and the mass distribution of the motorcycle.

Examples include motorcycles intended for use on public highways (for example road motorcycles or production motorcycles) and racing motorcycles comprising any one, any combination of any number, or all of the above-described features.

It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Each feature disclosed in the description, and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination.

Claims

1. A motorcycle engine comprising at least one cylinder, wherein the engine is adapted to be mounted in a motorcycle such that the cylinders are all inclined towards the rear of the motorcycle.

2. A motorcycle engine according to Claim 1, wherein the angle of inclination of a cylinder is between 12 degrees and 18 degrees to the vertical.

3. A motorcycle engine according to Claim 2, wherein the angle of inclination is about 15 degrees.

4. A motorcycle engine according to any of the preceding claims, wherein each cylinder is associated with a respective inlet aperture, the engine being adapted to be mounted in a motorcycle such that the inlet apertures face generally forwards.

5. A motorcycle engine comprising a plurality of cylinders, each cylinder being associated with a respective inlet aperture, the engine being adapted to be mδuntecin^'a rrrotorcy cle such that ^"*e^~inleTap^"ertϋres^"f ace^""generally forwards .

6. A motorcycle engine according to any of the preceding claims, each cylinder being associated with a respective exhaust aperture, the engine being adapted to be mounted in a motorcycle such that the exhaust apertures face generally rearwards.

7. A motorcycle engine comprising a plurality of cylinders, each cylinder being associated with a respective exhaust aperture, the engine being adapted to be mounted in a motorcycle such that the exhaust apertures face generally rearwards.

8. A motorcycle engine as claimed in any of the preceding claims, comprising an inlet aperture and an inlet passage in flow communication with the inlet aperture, the engine further comprising means for varying the length of the inlet passage.

9 A motorcycle engine, comprising an inlet aperture and an inlet passage in flow communication with the inlet aperture, the engine further comprising means for varying the length of the inlet passage.

10. A motorcycle engine according to Claim 8 or Claim 9, wherein the inlet passage comprises a throttle body mounted adjacent the inlet aperture and a trumpet movable mounted on the throttie body.

11. A motorcycle engine according to Claim 10, wherein the trumpet is slidably mounted on a guide shaft having a longitudinal axis disposed parallel to a longitudinal axis of the throttle body.

12. A motorcycle engine according to any of Claims 8 to 11, wherein the length adjusting means comprises an actuator for sliding the trumpet in a longitudinal direction on the guide shaft.

13. A motorcycle engine comprising a cooling system including a plurality of coolant passages for passing coolant through portions ofthe engine, wherein a first set of coolant passages having a first cross-sectional area and a second set of coolant passages having a second larger cross-sectional area.

14. A motorcycle engine according to Claim 13, further comprising a third set of coolant passages.

15. A motorcycle engine according to Claim 13 or Claim 14, comprising a coolant passage for passing coolant adjacent valve guides ofthe engine.

16. A motorcycle engine according to any of Claims 13 to 15, comprising a coolant passage for passing coolant adjacent valve seats of the engine.

17. A motorcycle engine according to any of Claims 13 to 16, comprising a coolant passage for passing coolant adjacent a portion of a cylinder housing of the engine adjacent a combustion chamber.

18. A motorcycle engine according to any of the preceding claims, comprising a cooling system, wherein the cooling system is adapted to be pressurised.

19. A motorcycle engine as claimed in any of the preceding claims, having a fuel injector arranged upstream of a throttle valve.

20. --A-motorcycle engine as claimed in any of the preceding claims, comprising a pneumatic valve.

21. A motorcycle engine according to any of the preceding claims, wherein all of the exhaust and inlet valves comprise pneumatic valves.

22. A motorcycle engine according to any of the preceding claims, wherein a cylmderhas^"^

23. A motorcycle engine according to any of claims 1 to 21, wherein a cylinder has three inlet valves and two exhaust valves associated therewith.

24. An motorcycle engine comprising a plurality of cylinders, each cylinder having a cylinder liner, wherein the cylinder liners are joined together.

25. A motorcycle engine comprising a connecting rod having a coating at at least one end.

26. A motorcycle engine according to Claim 25, wherein the coating is at the small end of the connecting rod.

27. A motorcycle engine according to Claim 25 or Claim 26, wherein the connecting rod comprises titanium.

28. A motorcycle engine according to any of Claims 25 to 27, wherein the connecting has a length of less than 100mm.

29. A motorcycle engine according to Claim 28, wherein the connecting rod has a length of less than 95mm.

30. A motorcycle engine according to any of the preceding claims, comprising a connecting rod-and arranged such that lateral thrust of the connecting rod is born at the small end thereof.

31. A motorcycle engine according to any of the preceding claims, comprising a clutch having a clutch plate comprising a carbon fibre material.

32. A motorcycle engine according to any of the preceding claims, wherein the clutch is adapted to allow some backslip.

33. A motorcycle engine according to any of the preceding claims, comprising a crankshaft having an axis of rotation, and means for introducing oil into an inlet of a bore in the crankshaft, wherein the inlet is located in the region of the axis of rotation of the crankshaft.

34. A motorcycle engine according to Claim 33, further comprising a seal associated with the inlet, wherein the seal comprises a magnetic seal.

35. A motorcycle engine according to any of the preceding claims, comprising a plurality of cylinders.

36. A motorcycle including a motorcycle engine according to any of Claims 1 to 35.

37. A connecting rod having a coating at at least one end.

38. A connecting rod according to Claim 37, wherein the coating is at the small end of the connecting rod.

39. A connecting rod according to Claim 37 or Claim 38, comprising titanium.

40. A connecting rod according to any of Claims 37 to 39, having a length of less - -than 100mm. ~

41. A connecting rod according to Claim 40, having a length of less than 95mm.

42. A clutch for a motorcycle, wherein the clutch is adapted to allow some backslip.

43. ^" ^-^ran shaft ^"fOr^"^^~mWorcy^"cle^"engin^"e the crankshaft^" having an axis of rotation, and including means for introducing oil into an inlet of a bore in the crankshaft, wherein the inlet is located in the region of the axis of rotation of the crankshaft.

44. A crankshaft arrangement for a motorcycle having an oil inlet and a seal associated with the inlet, wherein the seal comprises a magnetic seal.

45. Use of a magnetic seal in an engine for a motorcycle.

46. A motorcycle comprising an intake having an elongate mouth feeding an intake duct which passes through a headstock of the motorcycle.

47. A motorcycle having a single- or inline multi-cylinder engine mounted to a chassis thereof, said engine having an air inlet aperture, wherein the inlet aperture faces the front of the motorcycle.

48. A motorcycle according to Claim 47, wherein said engine further comprises an exhaust aperture, said exhaust port facing the rear of the motorcycle.

49. A production motorcycle according to Claim 47 or- Claim 48.-

50. A road motorcycle according to Claim 47 or Claim 48.

51. -A -motorcycle-having a-single--or-inline-multi_^cylinder engine mounted to a chassis thereof, wherein the or each cylinder of the engine is inclined towards the rear of the motorcycle.

52. A motorcycle according to Claim 51 , wherein the or each cylinder is inclined towards the rear of the motorcycle at an angle of less than 30°.

53.^" ATtfotorcyde ax yrding^'to Claim 51 , wherein the or each cylinder is inclined towards the rear of the motorcycle at an angle of between 10° and 20°.

54. A motorcycle according to Claim 51 , wherein the or each cylinder is inclined towards the rear of the motorcycle at an angle of between 12.5° and 17.5°.

55. A motorcycle according to Claim 51 , wherein the or each cylinder is inclined towards the rear of the motorcycle at an angle of 15°.

56. A system for supplying air to a motorcycle engine, said system comprising an air intake and means for conveying air from the air intake to an engine, wherein the conveying means has a length less than twice the direct distance between the engine and the air intake.

57. A system according to Claim 56, wherein the conveying means has length less than 1.5 times the direct distance between the engine and the air intake.

58. A system according to Claim 56 or Claim 57, wherein the conveying means has length substantially equal to the direct distance between the engine and the air intake.

59. A system according to any of Claims 56 to 58, wherein the conveying means conveys air from the air intake to an inlet aperture of the engine, said inlet

60. A system for exhausting gas from a motorcycle engine, said system comprising an exhaust canister and means for conveying gas from an engine to the exhaust canister, wherein the conveying means has a length less than twice the direct distance between the engine and the exhaust canister.

61. A system according to Claim 60, wherein the conveying means has length less ^"thah .5 times^"the direct α ancebetweerrthe en^'ginerand the exhaust canister.

62. A system according to Claim 60 or Claim 61, wherein the conveying means has length substantially equal to the direct distance between the engine and the exhaust canister.

63. A system according to any of Claims 60 to 62, wherein the conveying means conveys gas from exhaust aperture of the engine to the exhaust canister, said exhaust aperture facing the exhaust canister.

64. An engine comprising a crankshaft and a gearbox having an output sprocket, comprising means for causing the crankshaft and the output sprocket to rotate in opposing directions.

65. An engine according to Claim 64, comprising a further shaft between the crankshaft and the gearbox arranged to be driven by the crankshaft and to drive the gearbox.

66. An engine according to Claim 65, wherein the further shaft is a balancing shaft.

67. An engine according to any of Claims 64 to 66, comprising an odd number of cylinders.

68. An engine according -to Claim 67, comprising three cylinders.

69. An engine according to any of Claims 64 to 68, arranged to have an even firing order.

70. A motorcycle having an engine mounted to a chassis thereof, said engine comprising a crankshaft and a balancing shaft, wherein the balancing shaft is

^{^} is ose^"d^~b^"etweenH^^

71. An engine comprising a clutch primary and a balancing shaft having means for driving the clutch primary.

72. An engine comprising an idler shaft having driven means for driving the idler shaft and driving means for driving a clutch primary, a gearing ratio between the driven means and the driving means being greater than 1.

73. An engine according to Claim 72, wherein the-ratio is- greater than-h ;

74. An engine according to Claim 72 or Claim 73, wherein the driven means is a gear adapted to engage with a gear on a crankshaft.

75. An engine according to any of Claims 72 to 74, wherein the driving means is a gear adapted to engage with the clutch primary.

76. An engine according to any of Claims 72 to 75, wherein the engine is a four- stroke engine.

77. An engine according to any of Claims 72 to 76, wherein the engine is a multi- cylinder engine.

78. ^_Aτr^~eτιg_ne according to Claim 77, wherein the engine has an inline configuration.

79. A balancing shaft comprising a driven gear for driving the balancing shaft and a driving gear for driving a clutch primary.

80. A balancing shaft according to Claim 79, wherein the ratio of the driven gear to the driving gear is greater than 1.

81. A balancing shaft according to Claim 79 or Claim 80, comprising at least one balancing mass provided thereon for producing a torque on the shaft when the shaft is rotated.

82. A balancing shaft according to Claim 81, comprising a driven end balancing mass adjacent the driven gear.

83. A balancing shaft according to Claim 81 or Claim 82, comprising a driving end balancing mass adjacent the driving gear.

84. A balancing shaft according to Claim 83 , wherein the radius of the driving end mass is greater than the dedendum circle of the driving gear.

85. An engine balancing mechanism incorporating a balancing shaft as claimed in any of Claims 79 to 84.

86. An engine comprising a balancing mechanism according to Claim 85.

87. An engine according to Claim 86, wherein the engine is a four-stroke engine.

88. An engine according to Claim 86 or 87, wherein the engine is a multi-cylinder engine.

89. An engine- according- to -Claim -88, . wherein the -engine has an inline configuration.

90. An engine comprising a cylinder having an inlet port and an outlet port, wherein the inlet port and/or the outlet port is disposed at an angle of greater than 25° to a longitudinal axis of the cylinder.

91. Aτrengme^" cOmp^"risifrg^""a^" cylinder havin^'g^{^}aπ ^"inlet port and an outlet port, wherein the inlet port and/or the outlet port is disposed at an angle of greater than 30° to a longitudinal axis of the cylinder.

92. An engine comprising a cylinder having an inlet port and an outlet port, wherein the inlet port and/or the outlet port is disposed at an angle of greater than 35° to a longitudinal axis of the cylinder.

93. An engine comprising a cylinder having an inlet port and an outlet port, wherein the inlet port and/orthe outlet port is-disposed at an-angle-of greater than 40° to a longitudinal axis of the cylinder.

94. An engine comprising a cylinder having an inlet port and an outlet port, wherein the inlet port and/or the outlet port is disposed at an angle of greater than 45° to a longitudinal axis of the cylinder.

95. An engine comprising a cylinder having an inlet port and an outlet port, wherein the inlet port and/or the outlet port is disposed at an angle of greater than 50° to a longitudinal axis of the cylinder.

96. An engine comprising a cylinder having an inlet port and an outlet port, wherein the inlet port- and/or the outlet port is disposed at an angle of greater than 55° to a longitudinal axis of the cylinder.

97. ^"~An^""engine comprising a cylinder having ^"an inlet port" and an outlet port, wherein the inlet port and/or the outlet port is disposed at an angle of greater than 60° to a longitudinal axis of the cylinder.

98. An engine according to any of Claims 90 to 97, wherein the inlet port is disposed at a first angle to the longitudinal axis of the cylinder and the outlet port is disposed at a second angle to the longitudinal axis ofthe cylinder, and wherein the first angle is not equal to the second angle.

99. An engine according to any of Claims.9Q.to 58,_ wherein the engine is ajbur__ stroke engine.

100. An engine according to any of Claims 90 to 99, wherein the engine is a multi- cylinder engine.

101. An engine according to Claim 100, wherein the engine has an inline configuration.

102. An engine comprising a cylinder and an inlet valve and an exhaust valve, wherein the inlet valve and/or the exhaust valve is disposed at an angle of greater than 5° to a longitudinal axis of the cylinder.

103. An engine comprising a cylinder and an inlet valve and an exhaust valve, wherein the inlet valve and/or the exhaust valve is disposed at an angle of greater than 7° to a longitudinal axis of the cylinder.

104. An engine comprising a cylinder and an inlet valve and an exhaust valve, wherein the inlet valve and/or the exhaust valve is disposed at an angle of greater than 9° to a longitudinal axis of the cylinder.

105. An engine comprising a cylinder and an inlet valve and an exhaust valve, wherein the inlet valve and/or the exhaust valve is disposed at an angle of

- greater than 11 °-to a longitudinal axis of the cylinder.

106. An engine comprising a cylinder and an inlet valve and an exhaust valve, wherein the inlet valve and/or the exhaust valve is disposed at an angle of greater than 13° to a longitudinal axis of the cylinder.

107. An engine according to any of Claims 102 to 106, wherein the inlet valve is " 3isposed^"at^"a-firsrangl^"e to the lolϊgitudinai axis^" f the cylinder and the exhaust valve is disposed at second.angle to the-longitudinal axis of the cylinder, and wherein the first angle is not equal to the second angle.

108. An engine according to any of Claims 102 to 107, wherein the engine is a four-stroke engine.

109. An engine according to any of Claims 85 to 108, wherein the engine is a multi-cylinder engine.

110. An engine according to Claim 109, wherein the engine has an inline configuration.

111. A motorcycle engine having a stroke and a connecting rod, wherein the connecting rod has a length of substantially twice the stroke.

112. An engine according to Claim 111, wherein the engine is a four-stroke engine.

113. An engine according to Claim 111 or 112, wherein the engine is a multi- cylinder engine.

114. An engine according to Claim 113, wherein the engine has an inline configuration.

115. -An-engine comprising a-coolant pump, wherein the coolant pump is mounted on a cylinder block of the engine.

116. An engine according to Claim 115, being a motorcycle engine.

117. A motorcycle comprising an engine according to Claim 116.

118. An engine comprising a coolant pump, wherein the pump is driven by gears from a crankshaftofthe engine..

119. An engine according to Claim 118, wherein the pump is driven via an idler gear.

120. An engine according to Claim 119, wherein the idler gear forms part of a compound idler.

121. An engine according to any of Claims 118 to 120, being a motorcycle engine.

122. A motorcycle comprising an engine according to Claim 121.

123. An engine having a liquid cooling system including a heat exchanger or radiator mounted adjacent the engine, wherein at least one of an inlet aperture for feeding coolant into the system and an outlet aperture for taking fluid from the system to the heat exchanger or radiator is disposed in a face ofthe engine facing the heat exchanger or radiator.

124. An engine according to Claim 123, wherein the inlet aperture is disposed in a face of a cylinder block of the engine.

125. An engine according to Claim 123 or 124, wherein the outlet aperture is τlτspO^"sed^"in arface^""of the^~cylinder head.

126. An engine according to any of Claims 123 to 125, wherein the engine is a four-stroke engine.

127. An engine according to any of Claims 123 to 126, wherein the engine is a multi-cylinder engine.

128. A^~rT^" engine^"- according to^"^ has an inline configuration.

129. An engine comprising a cooling system for cooling first and second portions of the engine, wherein the first portion of the system is cooled more than the second portion.

130. An engine according to Claim 129, wherein the first portion is cooled by faster moving coolant and the second portion is cooled by slower moving coolant.

131. An engine according to Claim 129 or 130, wherein the coolant is a liquid.

132. An engine according to any of Claims 129 to 131, wherein the first portion includes one or more outlet ports of one or more cylinders of the engine.

133. An engine according to any of Claims 129 to 132, wherein the second portion includes one or more inlet ports of one or more cylinders of the engine.

134. An engine according to any of Claims 129 to 133, comprising a radiator or heat exchanger mounted adjacent the engine.

135. An engine according to any of Claims 129 to 134, further comprising at least one conduit for carrying coolant between an aperture in the engine and the radiator or heat exchanger, the conduit having a length substantially equal to the distance between the aperture and the radiator or heat exchanger.

136. A motorcycle comprising an engine according to any of Claims 129 to 135.

137. A motorcycle according to Claim 136, wherein a cylinder or cylinders of the engine are inclined towards the rear of the motorcycle.

138. A motorcycle engine comprising alubricant sump, wherein the lubricant sump

under gravity, if the orientation. of the engine about a lateral axis should change in use.

139. A motorcycle substantially as hereinbefore described with reference to one or more of the accompanying drawings.

140. A production motorcycle engine substantially as hereinbefore described with reference to one or more of the accompanying drawings.

141. A road motorcycle substantially as hereinbefore described with reference to one or more of the accompanying drawings.

142. A balancing shaft substantially as hereinbefore described with reference to one or more of the accompanying drawings.

143. A system for providing air to a motorcycle engine substantially as hereinbefore described with reference to one or more of the accompanying drawings.

144. A system for exhausting gas from a motorcycle engine substantially as hereinbefore described with reference to one or more of the accompanying drawings.

145. An engine substantially as hereinbefore described with reference to one or more of the accompanying drawings.

146. An engine balancing mechanism substantially as hereinbefore described with reference to one or more of the accompanying drawings.

147. A motorcycle engine substantially as hereinbefore described with reference to one^"or^"more^"ofthe^"accompanying drawings.

148. A lubrication system substantially as hereinbefore described with reference to one or more of the accompanying drawings.

149. A motorcycle chassis substantially as hereinbefore described with reference to one or more of the accompanying drawings.

150. A connecting rod substantially as hereinbefore described with reference to one or more of the accompanying drawings.

151. A clutch substantially as hereinbefore described with reference to one or more of the accompanying drawings.

152. A crankshaft substantially as hereinbefore described with reference to one or more of the accompanying drawings.

153. A crankshaft arrangement substantially as hereinbefore described with reference to one or more of the accompanying drawings.

I _ _ 154. Use of a magnetic seal substantially as hereinbefore described^" with reference to one or more of the accompanying drawings.