A two-stroke internal combustion engine having at least one cylinder with a combustion chamber defined between the cylinder head and a reciprocating piston, and a carburetor which delivers a rich fuel and air mixture to a compressor with a reciprocating piston driven by the engine to compress the mixture until the mixture is under sufficient pressure to open a differential pressure injection valve and thereby inject the mixture directly into the engine combustion chamber. The mixture is ignited by a spark plug to drive the engine piston through its power stroke and rotate its associated crankshaft which is connected to a crankshaft of the compressor to reciprocate its piston and thereby compress the fuel and air mixture and inject it into the cylinder in timed relation with the engine piston.