FOUR-STROKE INTERNAL COMBUSTION ENGINE AND EXHAUST VALVE

摘要

A cylinder portion configured such that a recess (depression) is formed on an upper edge portion of an inner wall of the cylinder portion to prevent the formation of choke between the inner wall and a side edge of a valve umbrella of an exhaust valve, the recess being formed by depressing the inner wall, and the exhaust valve configured such that a cross section of a head portion of the valve umbrella tapers from an outer peripheral edge of the valve umbrella toward a top of the valve umbrella are included.