CAM CHAIN DETACHMENT PREVENTIVE STRUCTURE

A conventional OHC internal combustion engine having a crankcase, a crankshaft supported in rolling bearings on the crankcase, and a valve train including a drive sprocket mounted on the crankshaft, and a camshaft timing chain wound around the drive sprocket is provided with a camshaft timing chain retaining plate for retaining the camshaft timing chain on the drive sprocket, and a push plug holding plate for holding a push plug pressed against the rolling bearing to restrain the rolling bearing from axial movement. According to the present invention, a camshaft timing chain retaining plate (31, 33) has an end part (31a, 33a) for preventing a camshaft timing chain (10) from falling off a drive sprocket (7), and a push plug holding part for holding a plush plug. The number of parts and assembling work can be reduced.