A DECOMPRESSION DEVICE OF A FOUR-STROKE CYCLE INTERNAL COMBUSTION ENGINE

摘要

A small and light decompression device of a four- stroke-cycle engine which cancels decompression operation surely when the engine rotational speed exceeds a predetermined speed to enable a stable engine starting. The device comprises an axial hole formed in a cam shaft , an oil pressure chamber formed in the axial hole, a decompression shaft reciprocating in accordance with oil pressure in the oil pressure chamber, a decompression pin which drives an exhaust valve to open in the compression stroke when the decompression shaft positions at a first position and stops the opening drive of the exhaust valve when the decompression shaft positions at a second position, a weight rotating in accordance with the engine rotational speed, and an oil pressure control valve interlocked with the weight to open and close a leak hole for controlling oil pressure in the oil pressure chamber.