Abstract: A high power, fuel efficient, low-emission, four-stroke, 6 cycle method of operation. A primary intake conduit carries air or a lean mixture from the compression chamber (crankcase) to the combustion chamber. Fuel is added to the air or lean mixture as it passes through the intake conduit. A secondary intake conduit runs from the compression chamber to ports in the cylinder located slightly above the bottom dead center position of the piston. Supplemental air or lean mixture from the compression chamber is fed to the combustion chamber through the secondary conduit when the piston is near its bottom dead center position. While the piston is in its bottom dead center position between its intake and compression strokes, the air or lean mixture from compression chamber provides a stratified charge in the combustion chamber, which is far more efficient than a homogeneous mixture, and has the further benefit of filling the cylinder from the bottom as well as from the top.