Air-cooled four-cycle engine.

摘要

In a four-cycle engine, the crankshaft (14) and the cam shaft (42) are disposed generally parallel to each other. Intake and exhaust ports (22, 21) are arranged in such a manner that a line (Y) passing through their centres is non-parallel to the axis (X) of the crankshaft (14). With this arrangement, intake and exhaust passages (32, 31) can be greatly shortened. Therefore, the intake efficiency as well as exhaust efficiency can be enhanced, thereby enhancing the performance of the engine. In an air-cooled engine, overheating of the engine is greatly restrained. <IMAGE>