Abstract: A reduced volume scavenging system for a two cycle engine embodying a duplex cylinder having an upper cylinder bore and a reduced-diameter lower cylinder bore. The lower bore communicates with a crankcase that houses a crankshaft, connecting rod(s) and engine lubricating oil. A fixed sleeve lines the upper cylinder bore and extends up into the cylinder head. A piston disposed for reciprocating motion within the fixed sleeve has an attached cylindrical, reciprocating sleeve that extends down into the lower cylinder bore and moves with the piston. The reciprocating sleeve has compression rings that seal the lower bore and the crankcase against blowyby gases that might contaminate the oil. The fixed sleeve has an intake opening in registry with an inlet port in the upper cylinder bore for admission of fresh air-fuel mixture.

Abstract: The engine has at least first and second stepped cylinders with the pistons therein operated from the same crankshaft at different portions of the engine cycle. The pistons in the cylinders to define a combustion space and first and second air compression spaces. The combustion space can expand a combusted fuel/air mixture and a double-acting air cylinder of the first cylinder is connected to deliver charging air to its own combustion space and deliver purging air to the combustion space of the other cylinder. Pressure lubrication for the cylinder walls is provided by oil sprays through openings in the piston skirts, with drainage back to the crankcase.

Abstract: A stratified-charge two-stroke internal combustion engine of the kind in which a rich mixture of fuel and air reaches each cylinder from an auxiliary transfer passage, and further air from a main transfer passage. The fuel-supply device for each cylinder is located in the auxiliary transfer passage well upstream of its entry into the cylinder so that substantial mixing of fuel and air takes place before entry. The rate of fuel supply is typically simply related to conditions in the auxiliary passage, and may be governed by a carburetor-type device located there or by a pressure-sensitive device located there and controlling a pump delivering through an injector. Multi-cylinder designs are described with a single fuel-supply device located in an auxiliary passage common to all the cylinders.

Abstract: A stepped piston for an engine of the kind having one or more cylinders, the or each cylinder containing a stepped piston having a pumping part of larger diameter, and a working part of smaller diameter, the working part of the piston being slidable in, and associated with, a working part of the cylinder in which combustion of a fuel/air mixture takes place, and the pumping part of the piston being slidable in, and associated with, a pumping part of the cylinder, the piston having a body with an interior hollow opening to the outside of a lower end of the piston, the body comprising a smaller diameter working, part, extending from the top of the piston to a step, and a larger diameter, pumping, part extending from the step to a lower end of the piston, at least one piston ring groove formed in an outer surface of the smaller diameter part and at least one piston ring groove formed in the outer surface of the larger diameter part, each piston ring groove, in use, receiving a piston ring the smaller diameter pa

Abstract: A crankchamber precompression type two-cycle internal combustion engine including at least one cylinder assembly, each cylinder assembly including a stepped cylinder constituted by a minor diameter cylinder portion and a major diameter cylinder portion, a stepped piston received in the stepped cylinder and constituted by a minor diameter piston portion and a major diameter piston portion adapted to be fitted in the minor diameter cylinder portion and the major diameter cylinder portion respectively, a crankchamber connected to the major diameter cylinder portion, a working chamber defined between the minor diameter cylinder portion and the minor diameter piston portion, and a sub-intake chamber defined between the major diameter cylinder portion and the minor diameter piston portion.

Abstract: Twin cylinder two cycle engine including a pair of stepped cylinders and a pair of stepped pistons slidable in said cylinders defining annular spaces of variable volume in said cylinders. The pistons are interconnected each other with 180.degree. phase difference. Air-fuel mixture introduced into the annular space in one cylinder is forced into the crankchamber of the other cylinder during the upward stroke of the associated piston, so that an additional charge is provided.

Abstract: A stepped piston two cycle engine, of the type including at least one set of two cylinders each such cylinder having a working part of smaller diameter and a pumping part of larger diameter, at least the air for each charge required by the working part of each cylinder of the set being pumped along transfer passage means from the pumping part of the other cylinder of the set, has the working part of each cylinder provided with exhaust port means, main inlet ports, and auxiliary inlet port means. The main inlet ports are arranged symetrically about and spaced from a plane which contains a longitudinal axis of the cylinder and which passes through the center of the exhaust port means, and the auxiliary inlet port means is provided in the cylinder wall opposite to the exhaust port means.