Abstract: In a two-stroke internal combustion engine with an engine block including a crankcase and a cylinder housing receiving pistons which are connected to a crankshaft by crosshead rods with crossheads guided for linear movement with the piston and a connecting rod extending between the crosshead and the crankshaft, wherein the cylinders have walls with inlet and outlet slits disposed above the bottom dead-center position of the piston and providing for communication between the cylinder and inlet and outlet channel structures formed in the cylinder housing around the pistons, the engine block consists of a cylinder housing and a crankcase joined along a dividing plane extending across the engine block below the lowest piston ring when the piston is in its bottom position and the cylinder housing includes channel structures which are open toward the dividing plane and have walls extending inwardly and have inner surfaces in engagement with the piston for guiding said piston and to form, with the piston skirt, the

Abstract: In a port-controlled two-stroke internal combustion engine with an engine block comprising a crankcase and a cylinder block including pistons connected to a crankshaft by crosshead rods with crossheads guided for linear movement with the pistons, and connecting rods extending between the crossheads and the crankshaft a partition structure is arranged between the crankcase and the cylinder block and includes hollow cylindrical sleeves which project axially into the cylinders to a point closely adjacent the undersides of the piston tops when the pistons are in their bottom dead center positions and the sleeves are spaced from the cylinder walls to form between the sleeves and the cylinder walls annular spaces for receiving the depending skirts of the pistons.