Structure of crankcase of four-stroke internal combustion engine

摘要

A structure of crankcase of four-stroke internal combustion engine, for sealing out the bore passing through the spacing walls of the crankcase that separate away the cam chain room, and the belt-type transmission room, to the crank shaft. The character of the structure being that the passing bore is sealed, with a ring seal of which the diameter is larger than the largest diameter of the bore under the situation of which the chain wheel is driving the cam chain to engage the crank shaft.