Patent ID: 7341027

Claim:
A portable 4-cycle engine allowing cooling air to flow in a direction of a crankshaft, comprising: a cylinder; a cylinder head disposed on said cylinder, and including a combustion chamber at a side of said cylinder; an intake port and an exhaust port, said intake port and said exhaust port being oppositely formed with each other in said cylinder head in a direction orthogonal to said crankshaft; a cooling fan for introducing the cooling air to said cylinder head, said cooling fan being connected to an end of the crankshaft; a valve train area formed above said intake port and said exhaust port, said valve train area being connected to said intake port and said exhaust port with a pair of valve guide bosses; and a plurality of vertical fins protruding upwardly from said cylinder head and extending in the direction of said crankshaft, wherein: said valve train area and said plurality of vertical fins are integrally formed with said cylinder head; said cylinder head, said intake port, said exhaust port, said valve guide bosses and a bottom of said valve train area together form an opening, through which the cooling air flows; and said opening is formed to have a decreasing cross-sectional area from an upwind side toward a downwind side of said cooling air.