Integrated power unit including split crankcase with reinforced fastening arrangement, and vehicle including same

Abstract

An integrated power unit for a small vehicle is configured to permit a compact engine design in a power unit having a crankcase that is split into upper and lower portions. The power unit includes a crankshaft supported by the crankcase and oriented transverse to the running direction of the vehicle. A transmission shaft is rotatably supported in a transmission chamber formed on the rear side of the crank chamber. The respective split surfaces of the upper and the lower crankcase portions are provided plural fastening boss portions arranged as vertically opposed pairs. The plural fastening boss portions are respectively joined using fastening bolts to integrate the upper crankcase and the lower crankcase, thereby forming the crankcase. A clutch is disposed at one end of the transmission shaft, and the rearmost fastening boss portions overlap with a rear portion of the clutch in the front-rear direction of the vehicle.