Piston-cylinder assembly

A piston-cylinder assembly for internal combustion engines comprising a cylinder having cylinder walls and means defining a top firing chamber, a crankcase communicating with said cylinder, a drive shaft in said crankcase, a piston in said cylinder operably connected to said drive shaft and arranged for reciprocating movement in said cylinder between upper and lower positions, a cup-like extension in said cylinder depending into said firing chamber, said piston having a top end wall, a depending skirt portion integral with said end wall and an upwardly extending tubular baffle integral with said end wall, said tubular baffle being of smaller diameter than said piston but of larger diameter than said cup-like extension whereby to receive the latter in the upper position of said piston, valve means mounted in said extension and cooperating with said cylinder for controlling the inlet of fuel and for scavenging exhaust gases, air passageway means extending from said crankcase to an upper portion of said cylinder which is above the top end wall of said piston and in the area of said baffle in said down position of said piston, and valve controlled air inlet means in said crankcase.