Patent US 5,490,482

A two cycle piston engine is described in which one or more intake poppet valves are carried in the top of the piston which driven onto a respective mating valve seat in the cylinder head by piston movement towards top dead center, a spring allowing retraction of the valve into the piston top after the poppet valve seats on its valve seat. A two valve arrangement opens one valve before the other, with air only in flowing through the first valve seat prior to opening of the other valve seat, through which fuel is injected.