JP2002326593A - Body frame for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To support an engine while well maintaining the balance of the strength and rigidity of a down frame formed by sticking both right and left half parts to each other. SOLUTION: The down frame 14 extending from a head pipe 12 in rear lower direction is formed by sticking a left side half part 21 of such a cross sectional shape as to be opened toward the right side of a body and a right side half part 22 of such a cross sectional shape as to be opened toward the left side of the body. The rear end part of the down frame 14 is formed in closed cross sectional shape. The area of the down frame 14 ranging from the rear end part to the intermediate part 24 at the front of the body are formed in a downward U-shape in cross section. A cross member 26 is installed across a lower end opening part at the intermediate part 24. The front part of the engine 3 is supported on the cross member 26, and the rear end part of the engine is supported on the rear end part at two positions in vertical direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motorcycle body frame in which a down frame extending downward from a head pipe and a seat frame are integrally formed.

[0002]

2. Description of the Related Art Conventionally, as this kind of motorcycle body frame, there is one disclosed in, for example, JP-A-2000-280962. The motorcycle body frame disclosed in this publication has a head pipe, a down frame extending rearward and downward from the head pipe, and a seat frame extending upward from the rear end of the down frame and integrally formed by casting. ing. Casting is performed using a mold that separates vertically.

For this reason, the head pipe and the seat frame are formed into a cylindrical shape extending in the vertical direction by the cylindrical cavities of the upper and lower molds, and the down frame is provided in the recess of the cavity of the upper mold. By projecting the projection from below, it is formed in an inverted U-shaped cross section that is opened downward. The body frame formed by casting in this manner has an engine mounted on a portion where the rear end of the down frame is connected to the lower end of the seat frame.

[0004]

SUMMARY OF THE INVENTION The inventors of the present invention have conceived of casting the above-described body frame into a left half of the vehicle body and a right half of the vehicle body, and joining these two halves together. I have. This is because the rigidity is low when the down frame has an inverted U-shaped cross section that is opened downward. That is, by adopting a structure in which the left half of the vehicle body and the right half of the vehicle body are joined, the down frame can be formed in a closed cross-sectional shape, and the rigidity can be improved.

However, in the down frame, since an auxiliary device must be inserted into a hollow portion formed therein or an opening must be formed for maintenance of the auxiliary device, a portion having high rigidity and a portion having low rigidity are required. And the engine may not be able to be supported in a well-balanced manner.

The present invention has been made in order to solve such a problem, and it is an object of the present invention to support an engine while maintaining a good balance of strength and rigidity of a down frame formed by joining both left and right halves. Aim.

[0007]

In order to achieve this object, a motorcycle body frame according to the present invention comprises a down frame extending rearward and downward from a head pipe and having a right side of a cross-sectional shape opened toward the left side of the vehicle body. The rear half of the down frame is formed into a closed cross-sectional shape by joining the half and the left half of the cross-sectional shape opened toward the right side of the vehicle body. A front halfway portion is formed in a U-shaped cross section downward, a cross member is laid across the lower end opening of the halfway portion, a front portion of the engine is supported by the cross member, and an engine rear end portion is formed at the rear end portion. Are supported at two locations in the vertical direction.

According to the present invention, the rear end portion of the engine is supported at the rear end portion of the down frame, which has relatively high rigidity, and the intermediate portion having relatively low rigidity is reinforced by the cross member. Since the front portion of the down frame is supported, the load caused by mounting the engine is similarly applied to the rear end portion and the middle portion of the down frame.

A motorcycle body frame according to a second aspect of the present invention is the motorcycle body frame according to the first aspect, wherein an engine support bracket is fixed to a rear end of the down frame. The rear end of the engine is supported by the down frame via the bracket. According to the present invention, the engine support bracket is made to function as an elastic material having a lower rigidity than that of the frame having the closed cross section, thereby reducing vibration transmitted from the rear end portion of the engine to the vehicle body frame and impact due to driving force of the engine. be able to.

A motorcycle body frame according to a third aspect of the present invention is the motorcycle body frame according to the first or second aspect of the present invention, wherein the motorcycle body frame according to the first or second aspect has two supporting portions for supporting an engine rear end portion. At least one of the parts has an elastic member interposed. According to the present invention, the vibration of the engine transmitted to the vehicle body frame can be reduced by the elastic member.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a motorcycle body frame according to the present invention will be described below in detail with reference to FIGS. FIG. 1 is a side view of a motorcycle using a motorcycle frame according to the present invention, FIG. 2 is an enlarged side view showing an engine mounting portion, and FIG. 3 is a side view showing an engine mounting portion of a body frame. The figure is drawn in a partially broken state. 4 is a plan view of a cross member for supporting the front part of the engine, FIG. 5 is a cross-sectional view taken along line V-V of the body frame and part of the engine in FIG. 2, and FIG. FIG. 7 is FIG.
8 is a sectional view taken along line VII-VII of the vehicle body frame, FIG. 8 is a transverse sectional view of the head pipe, and FIG. 9 is an enlarged sectional view showing a front support portion of the fuel tank. 10 and 11 are views showing another example of forming the head pipe.

In these figures, the reference numeral 1 denotes a motorcycle according to the present embodiment. The motorcycle 1 is assembled using a vehicle body frame 2 according to the present invention. Reference numeral 3 indicates an engine, 4 is a front wheel, 5 is a front fork, 6 is a steering wheel, 7 is a rear wheel, 8 is a rear arm, 9 is a cushion unit, 10 is a seat,
Reference numeral 11 denotes a fuel tank.

The front fork 5 is of a telescopic type and is rotatably supported by a head pipe 12 of a body frame 2 described later. The rear arm 8 includes a left arm 8a and a right arm 8 on both sides of the rear wheel 7.
b (see FIG. 6), and the pivot shaft 1
3 (see FIGS. 2 and 6) so as to be rotatable. The cushion unit 9 is interposed between the middle of each of the arms 8 a and 8 b of the rear arm 8 and the body frame 2.

As shown in FIG. 1, the vehicle body frame 2 includes the head pipe 12, a down frame 14 extending rearward and downward from the head pipe 12, and a seat frame extending upward from the rear end of the down frame 14. 15 and a rear frame 16 (see FIGS. 2 and 3) extending downward from the rear end of the down frame 14 are integrally formed. More specifically, as shown in FIGS. 5, 7 and 8, the vehicle body frame 2 is formed by joining a left body half 21 and a vehicle right half 22 by friction stir welding. ing.

The two halves 21 and 22 are formed by casting, respectively, and the left half 21 of the vehicle body has a cross-sectional shape opened toward the right side of the vehicle, and the right half 22 of the vehicle body has It has a cross-sectional shape that is open toward the left side of the vehicle body. That is, a mold (not shown) for molding these two halves 21 and 22 has a cavity formed by a concave portion and a convex portion, and a female mold having a concave portion and a male mold having a convex portion. Uses a structure that comes and goes in the vehicle width direction.

As shown in FIGS. 5, 7 and 8, the left half portion 21 of the vehicle body has a ridge 21a formed on the inner edge of the vehicle body, and the right half portion 22 of the vehicle body has the inner edge portion. A groove 21b into which the ridge 21a fits is formed on the edge. In order to join these two halves 21 and 22 to each other, the concave groove 21b and the ridge 21a are fitted and overlap each other in the thickness direction, and in this state, a rotary tool for friction stir welding is brought into contact with the outer surface. By doing it. After joining, the hole 12a (see FIG. 8) in the head pipe 12 is honed by machining to adjust the head pipe 12 to a predetermined size. In this embodiment, the edge portion of the right half portion 22 of the vehicle body forming the concave groove 21b is formed so as to be thicker than other portions. This is to prevent the joint from being deformed by buckling due to being pressed by the rotating tool when performing friction stir welding.

The head pipe 12 can be formed as shown in FIGS. 10 and 11 in addition to the above-described one. 10 and 11 show another example of forming the head pipe. FIG. 10 (a) is a plan view and FIG.
(B) is a longitudinal sectional view. In the head pipe shown in FIG. 10, rings 12b for press-fitting bearings are fixed to the upper and lower openings. The ring 12b can be fixed to the head pipe 12 by a friction stir welding method, brazing, welding, or the like.

After the ring 12b is fixed to the head pipe 12, the inner peripheral portion is finished by honing or the like. The position and shape of the inner peripheral surface of the ring 12b before the post-processing is shown by a two-dot chain line in FIG. By press-fitting a bearing for supporting the steering shaft into the ring 12b, it is possible to prevent a load at the time of press-fitting from being applied to the head pipe 12. Therefore, the steering shaft (not shown) can be firmly supported while employing a structure in which the head pipe 12 is formed by the left and right halves 21 and 22. In FIG. 10B, what is indicated by reference numeral 12c facing the inside of the head pipe 12 is an inner flange for positioning the ring 12b in the axial direction. The inner flange 12c is provided on both left and right halves 21,22.
Are formed integrally with each other. The head pipe 12 shown in FIG. 11 is formed separately from the left and right halves 21, 22.
Welded to both halves. The weld is indicated by reference numeral 12d.

By joining the left half 21 and the right half 22 of the vehicle body in this way, a hollow portion 23 is formed inside the vehicle body frame 2. In the vehicle body frame 2, a portion other than the middle portion 24 in the front-rear direction corresponding to the front portion of the engine 3 is formed in a closed cross-sectional shape.
Auxiliary devices such as the fuel tank 11 and the carburetor 25 are inserted and mounted in the device 3.

As shown in FIG. 5, the intermediate portion 24 is formed in a U-shaped cross section and is opened downward, and a cross member 26 is provided at a lower end opening 24a with the left half 21 of the vehicle body and the vehicle body. It hangs over the right half 22 and is laid horizontally. As shown in FIGS. 2, 4 and 5, a front bracket 27 for supporting the front part of the engine is attached to both ends of the cross member 26 in the vehicle width direction by bolts 28 for attaching the cross member.

The mounting bolts 28 are screwed from below into mounting seats 29 of the left and right halves 21 and 22 so that they can be easily attached and detached from the lower end opening. A coil 31 is mounted on the upper surface of the right side (the left side in FIG. 5) of the cross member 26 via a coil bracket 30. This coil 31 is for supplying power to the ignition plug P of the engine 3.

In FIG. 5, the reference numeral 32 provided above the cross member 26 is a bracket for supporting the rear end of the fuel tank 11. This bracket 32 is formed in a gate shape that is opened downward,
Both ends are fixed to the left and right halves 21 and 22 of the body frame 2 by fixing bolts 33. These fixing bolts 33 are attached to the mounting seats 3 of the two halves 21 and 22 from the inside of the vehicle body.
4 screwed.

In this embodiment, of the left and right fixing bolts 33, the fixing bolts 33 on the left side of the vehicle body are used.
The fuel cock support bracket 35 and the fuel tank support bracket 32 are fastened together to the left half 21 of the vehicle body. The fuel cock attached to the fuel cock supporting bracket 35 is indicated by reference numeral 36 in FIG.

The fuel tank 11 is formed by a blow molding method or a rotational molding method using synthetic resin as a material. The fuel tank supporting bracket 32 supports the rear end of the fuel tank 11 and the front end of the fuel tank 11 is supported by the down frame 14 of the vehicle body frame 2. Have been supported. The rear end of the fuel tank is supported by attaching a grommet 37 to the bracket 32 and fitting a support projection 38 projecting downward from the rear end of the fuel tank into a support hole 37a of the grommet 37 from above. Is going.

As shown in FIG. 9, the front end of the fuel tank is supported by screwing a fixing nut 40 to a cylindrical member 39 integrally projecting from the fuel tank 11 by insert molding. And flange 3 at the base of the tubular member
9a by sandwiching the supporting cylinder 42 of the vehicle body frame 2 via the sealing member 41. In FIG. 9, reference numeral 43 denotes a fueling cap.

The engine 3 of the motorcycle 1 is a four-cycle air-cooled single-cylinder engine. As shown in FIG. 2, a cylinder 3a is disposed so that an axis is directed in the front-rear direction of the vehicle body, and is provided in a crankcase 3b. 3 mounting bosses 5
1 to 53 are mounted on the vehicle body frame 2 by mounting bolts 54 to 56, respectively. The power of the engine 3 is transmitted from the output sprocket 57 provided at the left end of the vehicle body of the crankcase 3b to the rear wheel 7 via a chain (not shown). In this embodiment, the engine 3 is covered with an engine cover 58 in a state where the engine 3 is mounted on the vehicle body frame 2 as shown in FIG.

An intake pipe 61 is provided above the cylinder 3a.
The carburetor 25 is connected via a, and an exhaust pipe 62 is connected to the lower part of the cylinder 3a. The intake pipe 61 is formed so as to be inclined so as to be gradually eccentric to the rear of the vehicle body as it goes upward, and extends above the cross member 26 from the lower end opening portion of the halfway portion 24 of the vehicle body frame 2. I have. The carburetor 25 connected to the rear end of the intake pipe 61 is disposed behind the cross member 26 and connects to an intake duct 64 of an air cleaner 63 provided on the vehicle body frame 2.

Of the three bosses 51 to 53 for attaching the engine 3 to the body frame 2, the front boss 51 at the front end of the crankcase is attached to the front bracket 27 for supporting the engine, which extends downward from the cross member 26. The upper boss 52 and the lower boss 53 at the rear end of the crankcase are mounted to the rear frame 16 of the vehicle body frame 2 via a rear bracket 65 for supporting the engine. The rear bracket 65 constitutes an engine support bracket according to the second aspect of the present invention.

As shown in FIG. 6, a damper rubber 66 is interposed between the front boss 51 and the mounting bolt 54 and between the upper boss 52 and the mounting bolt 55. FIG. 6 shows a connecting portion between the upper boss 52 and the mounting bolt 55, but a connecting portion between the front boss 51 and the mounting bolt 54 has a structure equivalent to the structure shown in FIG. The other boss 53 is rigidly fixed to the rear bracket 65 via a mounting bolt 56. By interposing the damper rubber 66 at two of the three mounting portions in this manner, the vibration of the engine 3 transmitted to the vehicle body frame 2 can be reduced while the engine 3 is firmly supported. In addition to the structure of this embodiment, the engine 3 is mounted on the vehicle body frame 2 by fixing three bosses rigidly to the vehicle body frame 2 or by elastically supporting the upper boss 52 and the lower boss 53 on the front side. The boss 51 is rigidly fixed, the upper boss 51 is rigidly fixed by elastically supporting the front boss 51 and the lower boss 53, and the other boss is elastically supported by any one of the three bosses. Can be rigidly fixed, or all the bosses can be elastically supported, or can be appropriately changed.

As shown in FIG. 2, the rear bracket 65 for mounting the upper boss 52 and the lower boss 53 is formed in a plate shape, and two fixing bolts 67, 68 and the pivot shaft 13. The material forming the rear bracket 65 is steel,
Various materials such as an aluminum alloy, a magnesium alloy, and a fiber-reinforced plastic can be used. The rear frame 16 constitutes a part of the rear end of the down frame 14, and as shown in FIGS. 3 and 6, side walls 16a and 16b at both ends in the vehicle width direction, a front wall 16c, and a rear wall. Wall 1
6d and the bottom wall 16e are formed so as to be opened upward. Since the upper open portion of the rear frame 16 is closed by the down frame 14 of the vehicle body frame 2, the rear frame 16 has a closed cross-sectional shape as a result.

The rear frame 16 is formed integrally with cylindrical bosses 69 and 70 extending from one end to the other end in the vehicle width direction. The cylindrical bosses 69 and 70 support the pivot shaft 13. are doing. The pivot shaft 13 has a flange 13a integrally formed on one end and a nut 71 screwed on the other end. The pivot shaft 13 is provided between the flange 13a and the rear frame 16, and between the nut 71 and the rear frame 16. The nut 71 is fastened to the rear frame 16 in a state where the rear bracket 65 is sandwiched between them. The left arm 8a and the right arm 8b of the rear arm 8 are rotatably supported at both ends of the pivot shaft 13.

In order to mount the above-described engine 3 on the vehicle body frame 2, first, as shown in FIGS. 5 and 9, the fuel tank 11 is mounted on the down frame 14 first.
The fuel tank 11 is attached to the vehicle body frame 2 by attaching a support bracket 32 to the rear end of the fuel tank 11 in advance, and attaching the tubular member 39 at the front end of the fuel tank to the down frame front by the fastening structure. Fix it. Next, the bracket 32 is fixed to the down frame 14 together with the fuel cock 36 by the fixing bolt 33. A fuel hose (not shown) for connecting the fuel cock 36 and the fuel tank 11 is attached before the fuel tank 11 is inserted into the down frame 14.

In mounting the engine 3 on the vehicle body frame 2, first, the front bracket 27 is fixed to the front boss 51 at the front end of the crankcase by a mounting bolt 54, and the cross member 26 is temporarily assembled to the front bracket 27. . The engine 3 includes an intake pipe 61 and a carburetor 2.
5 is attached in advance. The connection between the carburetor 25 and the intake duct 64 is made by inserting a hand into the vehicle body frame 2 through an opening (not shown) on the seat frame 15 side after the engine is mounted.

Next, the front bracket 27, the cross member 26, the carburetor 25 and the like are inserted into the vehicle body frame 2 from the lower end opening portion of the halfway portion 24 of the vehicle body frame 2, and the upper boss 52 at the rear end of the engine is connected to the upper boss 52. The lower boss 53 and the rear bracket 65 are temporarily held by the mounting bolts 55 and 56. With the engine 3 temporarily held on the body frame 2 in this manner, the front bracket 27 and the cross member 26 are fixed to the down frame 14 by the mounting bolts 28. Then, the upper boss 52 and the lower boss 53 are fastened to the rear bracket 65 by the fixing bolts 55 and 56 with a regular tightening force.
The engine mounting operation is completed.

The vehicle body frame 2 configured as described above
The rear portion 16 of the engine is supported by the rear frame 16 having a relatively high rigidity and formed in a closed cross-sectional shape, and the intermediate portion 24 having a relatively low rigidity due to the formation of the lower end opening. Is reinforced by the cross member 26 to support the front portion of the engine 3 here.
Is similarly applied to the rear end (rear frame 16) of the down frame 14 and the intermediate portion 24.

Further, in the vehicle body frame 2, the rear bracket 65 can function as an elastic material, and vibration and impact transmitted from the engine rear end to the vehicle body frame 2 can be reduced. In this embodiment, a plate-shaped rear bracket 65 is interposed between the rear end of the engine and the vehicle body frame 2 in an upright state, so that the reaction force when the engine 3 drives the rear wheel 7 is provided. Can be improved in the direction in which the vehicle acts (the front-rear direction of the vehicle body), and the transmission of engine vibration in the vehicle width direction to the vehicle body frame 2 can be reduced.

Further, since the vehicle body frame 2 has the damper rubber 66 interposed between the upper boss 52 at the rear end of the engine and the mounting bolt 55, the vibration of the engine 3 transmitted to the vehicle body frame 2 is provided. Can be reduced by the damper rubber 66. Furthermore, in the vehicle body frame 2, by disposing the ignition coil 31 on the cross member 26, the coil 31 can be located near the ignition plug P.

The left half 2 of the vehicle body frame 2
1 and the right half 22 of the vehicle body can be joined by, for example, brazing in order to avoid sticking to the friction stir welding method.
Any method that does not melt the frame may be used. When brazing, the two halves 21,
A brazing material is applied to the joint in a state where 22 is combined, and the brazing material is melted and joined by a heating furnace.

In order to attach the rear end of the engine to the vehicle body frame 2, in addition to using the rear bracket 65 as described above, a bracket portion may be formed integrally with the rear frame 16 as shown in FIG. it can. 12A and 12B are diagrams showing another embodiment of the body frame. FIG. 12A is a side view of the rear frame portion, and FIG. 12B is a diagram showing the rear frame portion as viewed from the rear of the vehicle body. The figure is drawn in a state where the left side of the center line C in the vehicle width direction is broken.
(B) The broken position in the figure is shown by the BB line in the figure (a). FIG. 3C is a perspective view of the lower end of the rear frame. In these drawings, the same or equivalent members as those described with reference to FIGS. 1 to 11 are denoted by the same reference numerals, and detailed description will be appropriately omitted.

The rear frame 16 shown in FIG. 12 has an upper mounting plate 8 for mounting an upper boss 52 at the rear end of the engine.
1 and a lower mounting plate 82 for mounting the lower boss 53 are integrally formed at both ends in the vehicle width direction. These mounting plates 81 and 82 are made to protrude outward in the vehicle width direction from a main portion of the rear frame 16 having a closed cross section. Although not shown, a damper rubber equivalent to that in the above-described embodiment is interposed in a support system between the upper boss 52 and the upper mounting plate 81.

By adopting a configuration in which the rear end of the engine is directly attached to the rear frame 16, the number of parts and the number of assembly steps can be reduced, and the cost can be further reduced.

[0042]

As described above, according to the present invention, two portions of the rear end of the engine are supported by the rear end of the down frame, which has relatively high rigidity, and the intermediate portion having relatively low rigidity is provided. Since the front part of the engine is supported here by being reinforced by the cross member, the load caused by mounting the engine is similarly applied to the rear end part and the middle part of the down frame.

Therefore, the engine can be supported in a well-balanced manner by the down frame formed by joining the left and right halves together, so that the left and right halves of the motorcycle body frame according to the present invention are formed by casting. The rigidity can be improved while reducing the weight.

According to the second aspect of the present invention, the engine supporting bracket is made to function as an elastic material having a lower rigidity than that of the frame having the closed cross section, so that the vibration transmitted from the rear end of the engine to the vehicle body frame and the engine can be used. Impact due to driving force can be reduced. Therefore, when the left and right halves of the body frame are formed by casting, the thickness can be further reduced, and the weight can be further reduced.

According to the third aspect of the invention, the vibration of the engine transmitted to the vehicle body frame can be reduced by the elastic member. Therefore, a motorcycle body frame that does not give an occupant a discomfort despite the support rigidity being improved by connecting the two rear portions of the engine to the body frame can be realized.

[Brief description of the drawings]

FIG. 1 is a side view of a motorcycle using a motorcycle frame according to the present invention.

FIG. 2 is an enlarged side view showing an engine mounting portion.

FIG. 3 is a side view showing an engine mounting portion of the vehicle body frame.

FIG. 4 is a plan view of an engine front support cross member.

FIG. 5 is a sectional view taken along line VV of a part of the vehicle body frame and the engine in FIG. 2;

6 is a sectional view taken along line VI-VI of a part of the vehicle body frame and the engine in FIG. 2;

7 is a sectional view of the vehicle body frame in FIG. 2 taken along line VII-VII.

FIG. 8 is a cross-sectional view of the head pipe.

FIG. 9 is an enlarged sectional view showing a front support portion of the fuel tank.

FIG. 10 is a view showing another example of forming a head pipe.

FIG. 11 is a sectional view showing another example of forming a head pipe portion.

FIG. 12 is a view showing another embodiment of a vehicle body frame.

[Explanation of symbols]

2 ... body frame, 3 ... engine, 12 ... head pipe, 14 ... down frame, 15 ... seat frame, 2
DESCRIPTION OF SYMBOLS 1 ... Half part on the left side of a vehicle body, 22 ... Half part on the right side of a vehicle body, 24 ... Midway part, 26 ... Cross member, 27 ... Front bracket, 5
1 front boss, 52 upper boss, 53 lower boss, 54
~ 56 ... mounting bolts, 65 ... rear bracket, 66 ...
Damper rubber.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yushi Inoue 2500 Shinkai, Iwata-shi, Shizuoka Yamaha Motor Co., Ltd. F-term (reference) 3D011 AF03 AF05 AH01 AK13 AK14 AK31

Claims (3)

[Claims] 1. A down frame extending rearward from a head pipe is joined to a right half portion having a cross-sectional shape opened toward the left side of the vehicle body and a left half portion having a cross-sectional shape opened toward the right side of the vehicle body. The rear end of the down frame is formed in a closed cross-sectional shape, and a middle part of the vehicle body front side from the rear end is formed in a U-shape with a downward cross section, and a lower end opening portion of the middle part is formed. A body frame for a motorcycle, wherein a cross member is laid horizontally, the cross member supports a front portion of an engine, and the rear end portion supports two vertical portions of a rear end portion of the engine. 2. The motorcycle body frame according to claim 1, wherein an engine support bracket is fixed to a rear end of the down frame, and the rear end of the engine is supported by the down frame via the bracket. A body frame for a motorcycle characterized by the following. 3. The motorcycle body frame according to claim 1, wherein an elastic member is interposed in at least one of two support portions for supporting a rear end portion of the engine. Body frame for motorcycles.