Two-cycle internal-combustion engines in which the air pumped by a single supply-pump operated by and in unison with the engine is separated or divided into two separate and distinct streams, one of which passes to the working cylinder unchanged, while the other receives a supply of hydrocarbon on its way to the working cylinder. The stream to which no hydrocarbon is supplied ordinarily acts to more or less thoroughly expel the burned gases from the working cylinder prior to the formation of a new charge therein, and the two streams frequently reunite as they enter the working cylinder or shortly before entry thereinto.
