Internal combustion engine provided with decompressing means for the starting phase

摘要

A decompressing mechanism (D) for an internal combustion engine (E) is incorporated into a camshaft (15) provided with a bore (54) extending in the direction of the arrow (A) along the axis (L1) of rotation of the camshaft (15). The decompressing mechanism (D) includes a decompression member (80) formed by metal injection and integrally having a flyweight (81), a decompression cam (82) for exerting a valve-opening force through an exhaust rocker arm (48) on an exhaust valve, and an arm (83) connecting the flyweight (81) and the decompression cam (82). The flyweight (81) is supported for swing motion by a pin (71) on the camshaft (15). The axis (L2) of swing motion of the flyweight (81) is included in a plane (P4) substantially perpendicular to the axis (L1) of rotation, and does not intersect the axis (L1) of rotation and the bore (54) of the camshaft (15). The fully expanded decompression member (80) revolves in a cylindrical space of a small diameter around the camshaft (15).