Two-stroke internal combustion engine

A two-stroke supercharged multi-cylinder internal combustion engine, comprising in combination a cylinder block having cylinder bores formed therein, a cylinder head on an upper end of the cylindrical bores defining a main combustion chamber, a piston assembly in each of said cylinder bores and including a piston having a domed head and a connecting rod operatively connected to said piston for reciprocating same between top dead center and bottom dead center, said piston including means to reduce and control the escape of lubricating oil therepast, said means including said piston assembly having a piston skirt extending from said head, a pair of diametrically opposed wrist pin bosses in said skirt below said domed head, a wrist pin mounted within said bosses with a retainer ring installed in an annular groove formed in an outermost edge portion of each of said bosses adjacent outer ends of the wrist pin for restricting endwise movement of said wrist pin, said wrist pin operatively connecting said connecting rod to said piston, sealing "O" rings having high temperature resistance properties installed in an annular groove formed in each of said bosses of the piston adjacent to each end portion of the wrist pin after assembly to prevent the escape and discharge of lubricating oil therepast, at least two compression piston rings situated in spaced and parallel grooves in the head of said piston above said wrist pin bosses and at least one oil scraper ring mounted within an annular groove around the skirt close to a lower edge portion of said skirt, drain holes extending from said groove through said skirt to control and prevent the escape of lubricating oil past individual scavenging port and exhaust port openings, said oil scraper ring always remaining below lowermost edges of said scavenging port and said exhaust port opening when said piston is at top dead center of its stroke, a crankshaft mounted for rotation at a base of the said cylinder block, a re-circulating type constant pressure feed oil pump mounted in the base of said cylinder block and being operatively driven by said crankshaft, an oil pan enclosing the lower side of the cylinder block, said crankshaft and said oil pump, said pump being operatively connected to the lubricating system of said engine, said cylindrical bores having said individual scavenging port and exhaust port openings formed in the lower side of each cylindrical wall in the same plane and axial position, said scavenging port lower side opening inclining inwardly and upwardly towards the walls of the cylinder, said scavenging port and exhaust port openings being both uncovered and covered simultaneously by the reciprocating piston passing thereby.