Two-cycle internal-combustion engines in which separate and distinct working and pumping pistons operate in a single cylinder a portion of which together with the working piston, forms a motor, while another portion of such cylinder, together with the pumping-piston forms a pump for supplying a fresh charge to the working cylinder. The supply-pump is operated by and in unison with the engine, and as the supply-pump and motor elements of the engine are all contained in a single cylinder the two sets of elements are necessarily inseparable without wholly defeating the operation of the engine in the manner contemplated.
