A two stroke combustion engine, equipped with fuel injection apparatus and ignition timing controlled by throttle position, has a charge forming device which delivers a rich fuel mixture from an integral float-type fuel chamber. The fuel injection apparatus typically comprises a tuned injector tube that communicates between a crankcase injector port and a cylinder injector port. The vast majority of fuel mixes with air in an injector mixing passage of the charge forming device where it is subsequently delivered to the tuned injector tube which directly injects the rich fuel mixture into a cylinder of the engine. The rich fuel mixture supplied by the charge forming device injects into the combustion chamber through the cylinder injector port via a reflected pressure wave generated from the previous combustion cycle. A primary air circuit of the charge forming device delivers a substantially lean mixture of fuel-and-air into the crankcase at high engine speeds where it flows from the crankcase through an air feed passage and into the combustion chamber. At idle and low speed engine conditions where throttle position is less than fifty percent open, ignition timing is predominately used to control engine operation. This feature simplifies design and calibration of the charge forming device while improving engine performance at extremely low fuel demands and load conditions.