Abstract: An engine includes: a crankcase; a cover that is connected to the crankcase at a mating surface of the cover inclined toward an inner side in a vehicle width direction in going downward when the engine is mounted to a vehicle body, the cover covering a protruding end of a rotary shaft; and attachment bosses that are formed to be integral with the cover, have a predetermined height from the mating surface, and accept fastening members for fastening the cover to the crankcase. Accordingly, when mounted on a two-wheeled motor vehicle, the engine can restrain protrusion in the vehicle width direction and can be disposed at a position as low as possible with reference to the vehicle.

Abstract: An engine includes: a crankcase; a cover that is connected to the crankcase at a mating surface of the cover inclined toward an inner side in a vehicle width direction in going downward when the engine is mounted to a vehicle body, the cover covering a protruding end of a rotary shaft; and attachment bosses that are formed to be integral with the cover, have a predetermined height from the mating surface, and accept fastening members for fastening the cover to the crankcase. Accordingly, when mounted on a two-wheeled motor vehicle, the engine can restrain protrusion in the vehicle width direction and can be disposed at a position as low as possible with reference to the vehicle.

Abstract: In an internal combustion engine with a balancer including a crankcase having a pair of wall portions, a crankshaft supported for rotation on the wall portions and having a balancer driving gear wheel provided thereon, and a balancer shaft supported for rotation by the wall portions and having a balancer driven gear wheel provided thereon, both gear wheels are disposed between the wall portions. A positioning mark including a set of marks provided on side faces in the same direction of the gear wheels is disposed near to pitch circles of both gear wheels. At a position opposing to both side faces of the one wall portion on the side opposing to the positioning mark on the pitch circles of both gear wheels, a through-hole extending through the one side wall is provided to permit the positioning mark to be visually observed through the through-hole.

Abstract: A lubrication structure for a bearing section of an internal combustion engine including a crankcase having a wall portion, a bearing secured to the wall portion, a rotational shaft supported for rotation by the bearing, and a bearing restriction member disposed on a side face of an outer race portion of the bearing and configured to suppress coming off of the bearing, wherein an oil receiving portion formed in a swollen state on the wall portion along an outer periphery on the outer side of an outer periphery below the center axis of the bearing, and an oil reserve section is provided so as to extend over the oil receiving portion and the bearing restriction member.

Abstract: In an internal combustion engine with a balancer including a crankcase having a pair of wall portions, a crankshaft supported for rotation on the wall portions and having a balancer driving gear wheel provided thereon, and a balancer shaft supported for rotation by the wall portions and having a balancer driven gear wheel provided thereon, both gear wheels are disposed between the wall portions. A positioning mark including a set of marks provided on side faces in the same direction of the gear wheels is disposed near to pitch circles of both gear wheels. At a position opposing to both side faces of the one wall portion on the side opposing to the positioning mark on the pitch circles of both gear wheels, a through-hole extending through the one side wall is provided to permit the positioning mark to be visually observed through the through-hole.

Abstract: A lubrication structure for a bearing section of an internal combustion engine including a crankcase having a wall portion, a bearing secured to the wall portion, a rotational shaft supported for rotation by the bearing, and a bearing restriction member disposed on a side face of an outer race portion of the bearing and configured to suppress coming off of the bearing, wherein an oil receiving portion formed in a swollen state on the wall portion along an outer periphery on the outer side of an outer periphery below the center axis of the bearing, and an oil reserve section is provided so as to extend over the oil receiving portion and the bearing restriction member.

Abstract: An internal combustion engine is provided with a crankcase partitioned into an upper section and a lower section. A fastening bolt is provided for fastening the upper and lower crankcase sections together in the vicinity of a crankshaft. A bolt hole is formed in the crankcase, and the fastening bolt is inserted and tightened in the bolt hole. An opening is formed at an end of the bolt hole within the upper crankcase, the end of the bolt hole is made to communicate with this opening, and the end of the fastening bolt protrudes into the opening when the engine is assembled, to lighten the crankcase, and in order to avoid concentrating stress in the bolt hole near the end of the bolt.

Abstract: An internal combustion engine is provided with a crankcase partitioned into an upper section and a lower section. A fastening bolt is provided for fastening the upper and lower crankcase sections together in the vicinity of a crankshaft. A bolt hole is formed in the crankcase, and the fastening bolt is inserted and tightened in the bolt hole. An opening is formed at an end of the bolt hole within the upper crankcase, the end of the bolt hole is made to communicate with this opening, and the end of the fastening bolt protrudes into the opening when the engine is assembled, to lighten the crankcase, and in order to avoid concentrating stress in the bolt hole near the end of the bolt.

Abstract: A structure for transmitting the power of a motorcycle engine includes an intermediate shaft arranged between a crankshaft and an input shaft of a transmission, and a method for making the structure. The structure and the method have the objective of shortening the distances between these three shafts, improving workability of assembling, and providing freedom of setting a speed reduction ratio. An intermediate shaft driven gear and an intermediate shaft driving gear having a diameter smaller than the intermediate shaft driven gear and are mounted in two steps, with the former overlaid on the latter, on an end of the intermediate shaft projecting outside a right case. Similarly, the intermediate shaft driven gear is engaged with a primary gear of the crankshaft, and the intermediate shaft driving gear is engaged with a primary driven gear of the input shaft at a location outside the right case.

Abstract: A structure for transmitting the power of a motorcycle engine includes an intermediate shaft arranged between a crankshaft and an input shaft of a transmission, and a method for making the structure. The structure and the method have the objective of shortening the distances between these three shafts, improving workability of assembling, and providing freedom of setting a speed reduction ratio. An intermediate shaft driven gear and an intermediate shaft driving gear having a diameter smaller than the intermediate shaft driven gear and are mounted in two steps, with the former overlaid on the latter, on an end of the intermediate shaft projecting outside a right case. Similarly, the intermediate shaft driven gear is engaged with a primary gear of the crankshaft, and the intermediate shaft driving gear is engaged with a primary driven gear of the input shaft at a location outside the right case.

Abstract: A structure for transmitting the power of a motorcycle engine includes an intermediate shaft arranged between a crankshaft and an input shaft of a transmission, and a method for making the structure. The structure and the method have the objective of shortening the distances between these three shafts, improving workability of assembling, and providing freedom of setting a speed reduction ratio. An intermediate shaft driven gear and an intermediate shaft driving gear having a diameter smaller than the intermediate shaft driven gear and are mounted in two steps, with the former overlaid on the latter, on an end of the intermediate shaft projecting outside a right case. Similarly, the intermediate shaft driven gear is engaged with a primary gear of the crankshaft, and the intermediate shaft driving gear is engaged with a primary driven gear of the input shaft at a location outside the right case.

Abstract: An oil pump is formed by a main body portion, a base, and a pump cover, and is provided with a rotor rotational shaft. The oil pump is formed with a main pump and a sub pump. The oil pump is attached to bond with a wall face of a thick-walled portion of a crankcase. A relief valve chamber is provided in the thick-walled portion in parallel with the rotor rotational shaft. A relief valve is contained therein in parallel with the rotor rotational shaft. A surrounding space in the relief valve chamber is directly connected to a pumping portion of the oil pump. This combination of elements and configuration provides for an oil pump that operates with efficiency, and that is small in size, light in weight.

Abstract: An oil pump is formed by a main body portion, a base, and a pump cover, and is provided with a rotor rotational shaft. The oil pump is formed with a main pump and a sub pump. The oil pump is attached to bond with a wall face of a thick-walled portion of a crankcase. A relief valve chamber is provided in the thick-walled portion in parallel with the rotor rotational shaft. A relief valve is contained therein in parallel with the rotor rotational shaft. A surrounding space in the relief valve chamber is directly connected to a pumping portion of the oil pump. This combination of elements and configuration provides for an oil pump that operates with efficiency, and that is small in size, light in weight.

Abstract: A structure for transmitting the power of a motorcycle engine includes an intermediate shaft arranged between a crankshaft and an input shaft of a transmission, and a method for making the structure. The structure and the method have the objective of shortening the distances between these three shafts, improving workability of assembling, and providing freedom of setting a speed reduction ratio. An intermediate shaft driven gear and an intermediate shaft driving gear having a diameter smaller than the intermediate shaft driven gear and are mounted in two steps, with the former overlaid on the latter, on an end of the intermediate shaft projecting outside a right case. Similarly, the intermediate shaft driven gear is engaged with a primary gear of the crankshaft, and the intermediate shaft driving gear is engaged with a primary driven gear of the input shaft at a location outside the right case.

Abstract: A cooling water passage structure for connecting cooling water passages in cylinders forming a V-shape in a water cooled type V-shaped internal combustion engine. A front cooling water passage of a front cylinder communicates with a front cooling water passage of a front cylinder head. A rear cooling water passage of a rear cylinder communicates with a rear cooling water passage of a rear cylinder head. Water pipes and cylindrical portions project from opposed positions of the front and rear cylinders and extend in one straight line. A connecting pipe is formed of rubber and is inserted in the water pipes. Ring clips and are engaged with annular grooves formed on the outer circumference of the connecting pipe at the front ends of the water pipes. O-rings are engaged with the outer circumference of the connecting pipe near the opposite ends thereof. The water pipes are connected to each other in a water tight manner.

Abstract: A water pump for feeding water under the action of centrifugal force created by rotation of an impeller disposed within a pump case includes a cooling water discharge port formed at a position offset in the axial direction of the pump from the outer peripheral portion of the impeller. A flow path structure having a projecting portion for guiding cooling water from the outer peripheral portion of the impeller up to the discharge port is intended to provide a flow path structure capable of smoothing the flow of cooling water, thereby increasing the amount of cooling water discharged and improving the pumping performance.

Abstract: A compact filter structure is provided having a cylindrical body disposed in the expansion chamber of a muffler. A tail pipe is inserted into the filter. The diameter of the filter is greater than that of the tail pipe. The filtering function of the body and the noise reducing function of the tail pipe are separated from each other. The filter structure can be formed in a compact construction which provides a large filtering capacity.