Abstract: A camshaft support structure for an internal combustion engine includes a cylinder head, a camshaft, a plurality of bearings, an auxiliary machine drive cam, an auxiliary machine, and a pulsar plate. The plurality of bearings include a terminal bearing supporting the camshaft to be rotatable with respect to the cylinder head about a rotational axis. The auxiliary machine has a plunger provided to be moved forward and backward by the auxiliary machine drive cam. The pulsar plate projects from the camshaft in a radial direction of the camshaft and is provided on an opposite side of the auxiliary machine drive cam with respect to the terminal bearing. The pulsar plate has a second surface facing the terminal bearing in the axial direction. Each of the first surface and the second surface is provided to slidably contact the terminal bearing.

Abstract: A detent structure for a rocker shaft includes a camshaft, a rocker shaft, a shaft support, and a detent part. The camshaft is provided at a cylinder head of an engine. The shaft support is provided at the cylinder head to support the rocker shaft and has a support surface supporting the rocker shaft. The detent part is to prevent rotation of the rocker shaft. The detent part includes a bolt insertion hole and a detent bolt. The bolt insertion hole is displaced from a central axis of the rocker shaft and passes through the rocker shaft. The detent bolt is provided in the bolt insertion hole and is fastened to the shaft support to pass across the support surface.