Abstract: A stepped-piston, internal-combustion engine includes at least one cylinder, each cylinder having a working part of lesser diameter defined by a cylindrical wall and a pumping part of greater diameter, a piston slidable in each cylinder, a receiver which is partly delimited by the cylindrical wall of the working part of each cylinder and which extends at least partly around each working part, working inlet ports in the cylindrical wall and extending between the working part of the cylinder and the receiver and valve means to control the entry of charge into the pumping part of each cylinder and the transfer of charge from said pumping part to the receiver, and wherein the admission of charge into the working part of each cylinder from the receiver is controlled by the uncovering of the working inlet ports by the working part of the piston.

Abstract: A stepped piston engine comprises first (10), second (11) and third (12) stepped cylinders, each cylinders (10,11,12) having a larger diameter pumping part (10p,11p,12p), and a smaller diameter working part (10w,11w,12w), and a piston (13,14,15) slidable in the cylinder, each piston (13,14,15) being coupled to an output shaft (16) of the engine, first transfer passage means (20) to transfer the precompressed charge from the larger diameter pumping part (10p) of the first cylinder (10) to the smaller diameter working part (11w) of the second cylinder (11), second transfer passage means (21), to transfer precompressed charge from the larger diameter pumping part (11p) of the second cylinder (11) to the smaller diameter working part (124) of the third cylinder (12), and third transfer passage means (22) to transfer precompressed charge from the larger diameter pumping part (12p) of the third cylinder (12) to the smaller diameter working part (10w) of the first cylinder (10).

Abstract: An internal combustion engine has a pair of stepped cylinders (14,15) in which stepped pistons (P1,P2) are received, each cylinder (14,15) and piston (P1,P2) having a pumping part of larger diameter and a working part of smaller diameter transfer paths from each of the pumping parts of each cylinder to the working part of the other comprising first passage parts (27,27') extending from the pumping parts (15a,14a) to second passage parts (28,28') and third passage parts comprising at least two branches (29,29') connecting the second passage parts (28,28') and the working parts (16a,16b) of the cylinder, the first (27,27') and third (29,29') passage parts each crossing an interface (1) between the crankcase 12 and cylinder block (11) via aligned parts, and the second passage parts (28,28') being wholly contained in the crankcase (12).

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 two-stroke internal combustion engine having a stepped piston in which the cylinder casting has a bore of greater diameter to form a pumping part, a bore of lesser diameter to form a working part, exhaust port means in the working part and opposed transfer port means on opposite sides of the working part disposed symmetrically about a plane passing through the longitudinal axis of the cylinder and center of the exhaust port means, the transfer port means being of a form to be produced in the casting process by non-separate cores introduced linearly towards the plane.

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.

Abstract: A loop driven vehicle such as a motor cycle has a pivoted fork which supports the rear wheel mounted on the engine unit, and the engine unit mounted at its rear on the frame of the vehicle by a mounting which permits angular movement of the engine unit about a second axis parallel to the axis of rotation of the rear wheel, and fore and aft movement of the second axis. This movement of the engine unit is accommodated by one or more second mountings which permit the fore and aft and angular movement and may constrain the engine unit against movement in other directions. The mounting at the rear of the engine unit may comprise a pivoted member, or a flexible plate secured between the engine unit and frame.