Power transmission unit for a motorcycle

A power transmission unit for a motorcycle having a body frame, the transmission unit comprising:

• a power unit case consisting of a crankcase and a transmission case for an engine mounted on the body frame, said crackcase and transmission case being integrated one with another;
• a bevel gear assembly;
• a countershaft in said transmission case;
• and a final shaft adapted to drive a rear wheel;
• said power unit case including a bevel gear case accommodating therein said bevel gear assembly, said bevel gear assembly including a driving bevel gear which is operatively connected with said countershaft in said transmission case, a driven bevel gear meshing with said driving bevel gear and operatively connected with said final shaft, and bearing means fitted in bearing holders which are fixedly secured to said bevel gear case by means of tightening bolts, said bearing means rotatably supporting said driving and driven bevel gears in said bevel gear case, said driving bevel gear being splined fitted onto said countershaft as it is rotatably supported by said bearing means in the bearing holder therefor, whereby the bevel gear assembly is mounted on and can be dismounted from the power unit case with both the driving and driven bevel gears incorporated in the bevel gear assembly.