Handheld type four-cycle engine

In a handheld type OHV engine, an oil tank (13) is provided so as to be connected to one side wall running the length of a crankcase (6) and a cylinder block (7), the oil tank (13) houses oil mist generation means (36,37,38,39,40) to and a rotational movement section of a valve operation mechanism, and the oil mist generated in the oil tank is supplied from a crank chamber to a valve operation chamber of a cylinder head housing a reciprocating movement section of the valve operation mechanism, and is returned to the oil tank by utilising the pressure pulsations of the crank chamber and a one-way valve (51). It is thus possible to lubricate the inside of the crank chamber and the valve operation mechanism reliably regardless of the operational position of the handheld type OHV engine while reducing the overall height of the engine.