Internal combustion engine

An internal combustion engine comprising a cylinder, a cylinder head for said cylinder providing a combustion chamber having inlet and exhaust ports, means comprising a main inlet passage and a fuel injection device for supplying an air-fuel mixture to said inlet port, a throttle valve provided in said main inlet passage, a spark plug threadedly fixed in said cylinder head and having a spark gap disposed at a predetermined position in said combustion chamber, an injection chamber provided in the cylinder head close to said spark gap, an injection port providing communication between said combustion chamber and said injection chamber, said injection port being disposed near to said spark gap and being directed to said spark gap and transversely of the axis of said cylinder, a secondary inlet passage means communicating with said injection chamber, a secondary inlet valve positioned in advance of said injection chamber for opening and closing the secondary inlet passage means, and an operating mechanism for opening and closing said secondary inlet valve, said mechanism being operated so that said secondary inlet valve is open during substantially the entire suction stroke of the engine, said injection port being positioned to discharge gas in said injection chamber substantially toward said spark gap so that gas is strongly injected toward or around said spark gap due to high negative pressure produced in said combustion chamber during a suction stroke of the engine, the discharge of gas from said port creating turbulence in said combustion chamber and scavenging previously formed exhaust gases from the region of said gap.