Structure of cylinder head of air cooling engine

Disclosed is a structure of cylinder head (52) of air cooling engine (3). The cylinder head (52) forms a longitudinal channel (7) between a valve driving member (522) and a combustion chamber (523) and extending completely therethrough in a direction of an intake port (524) and an exhaust port (525). The cylinder head (52) also forms a lateral channel (6) that is located between the exhaust port (525) and the intake port (524) and opening toward a spark plug seat (526) and communicates the longitudinal channel (7). The engine (3) is structured by arranging the exhaust port (525) of the cylinder head (52) toward a vehicle front side and arranging the intake port (524) toward a vehicle rear side. When a vehicle is moving, an external cooling air stream flows from the exhaust port (525) through the longitudinal channel (7) to reach and discharge through the intake port (524) side.