Engine supercharged in crankcase chamber

A four-cycle, crankcase compression, internal combustion engine comprised of a cylinder block defining at least one cylinder bore, a cylinder head affixed to said cylinder block in closing relation to one end of said cylinder bore and forming a combustion chamber with said cylinder bore, a crankcase member affixed to said cylinder block in closing relationship to the other end of said cylinder bore and forming a crankcase chamber with said cylinder block, a piston reciprocating in said cylinder bore and separating said combustion chamber from said crankcase chamber, a crankshaft rotatably journaled in said crankcase chamber, means for driving said crankshaft from the reciprocation of said piston, timed intake and exhaust valves for permitting a charge to enter said combustion chamber and to permit a burned charge to be discharged from said combustion chamber, atmospheric air intake means for delivering a atmospheric air charge to said crankcase chamber for compression therein, a first control valve for controlling the communication of the atmospheric air with said crankcase chamber so that air can only enter said crankcase chamber from said atmospheric air intake means, a second control valve for controlling the communication of said crankcase chamber with a pressure chamber for permitting a compressed charge to flow only from said crankcase chamber to said pressure chamber, a pressure passage communicating said pressure chamber with said intake valve, a supercharger bypass passage extending between said pressure chamber and said crankcase chamber at a point between said two control valves for controlling the maximum pressure in said pressure passage.