Patent ID: 7267095

Claim:
A power unit comprising: an internal combustion engine including: a crank shaft, a transmission mechanism with an endless chain wound around a drive sprocket and a driven sprocket, an auxiliary machine which is rotated by the transmission mechanism, a crankcase which houses the transmission mechanism, the auxiliary machine and the crank shaft, the auxiliary machine being fitted to the crankcase, and a crankcase cover adapted to cover an opening formed by an opening formation area as part of a side wall of the crankcase in an axial direction, the crankcase cover being joined to a mating face of the opening formation area, thereby covering the opening; and a transmission having an input shaft, power of the crank shaft being transmitted to the input shaft, wherein the drive sprocket is fitted to the input shaft, and the driven sprocket is fitted to a fitting part of a drive shaft of the auxiliary machine, and when viewed sideways, the opening formation area has an overlapping part overlapping a portion of the driven sprocket so that the side wall covers part of the driven sprocket, and wherein all of the fitting part and a non-overlapped portion of the driven sprocket are exposed inside the opening when viewed in the axial direction of the driven sprocket.