| 摘要 |
The power unit for a motorcycle accodring to the present invention comprises an engine unit having a casing in which a crankshaft and a countershaft are rotatably supported in parallel to each other, and a transmission unit having a casing in which a transmission input shaft and a transmission output shaft are rotatably supported in parallel to each other to define a dry belt drive-type transmission device. Said transmission input shaft of the transmission unit is being connected to the countershaft of the engine unit so as to be rotatable together with the countershaft. A cooling fan chamber is provided at a joined portion of the casing of the engine unit to the casing of the transmission unit, said cooling fan chamber is communicated with inside and outside of the casing of the transmission unit. A cooling fan is disposed in said cooling fan chamber so as to rotate together with the connecting portion of the countershaft and the transmission input shaft in a vicinity of said connection section. The cooling fan introduces cooling air into the casing of the transmission unit.
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