CYLINDER HEAD FOR AN INTERNAL COMBUSTION ENGINE, ENGINE INCORPORATING THE CYLINDER HEAD, AND METHOD OF MAKING SAME

摘要

A motorcycle includes an engine configured to expel an exhaust from combustion chambers of cylinders in a cylinder head through exhaust ports. Each of the cylinders is provided with a recessed portion provided in an exhaust passage wall surface in a central portion of an exhaust passage of a corresponding exhaust port. This makes it possible to maintain flow rate and flow velocity of the exhaust gas, and to decrease exhaust loss. As a result, it is possible to increase engine torque by use of a simple structure. In addition, no restriction is imposed on the layout of parts around the engine, because the recessed portions are provided in the exhaust ports.