The invention provides a
piston four stroke engine, comprising a valve actuating mechanism, an ignition device and a fueling
injection device, which are arranged on
cylinder head, wherein the actuating mechanism comprises a
valve stem the external end of which is connected with an
electromagnet component and the
electromagnet component is composed of an upper
electromagnet and a lower electromagnet which are in coaxial connection. The invention has the advantages that an electromagnetic
magnetic circuit close is used as power to control immutable
stroke of open and close of an air valve; a valve spring is not provided and motion line speed of the air valve is high; when air inflows, an intake valve can realize full open under the full
stroke of descent of the
piston, thereby ensuring full
stroke air inflow for descent of the
piston upward and sufficient air inflow; when exhausting the air, an
exhaust valve can realize full open under the full stroke descent of the piston and for the piston stroking upward, thereby ensuring full stroke exhaust air for the piston stroking upward; and drift
diameter of the
exhaust valve is larger than that of the intake valve, the
exhaust valve has small resistance and complete exhaust. When being in a state of high speed,
lag behind and springback for the air valve does not occur, thereby eliminating air cross interference caused by an over-lapping angle of the air valve, implementing purification inside the engine, improving fuel availability and reducing environmental
pollution.