Abstract: Disclosed is a two-cycle internal combustion engine including a protruding edge portion formed in a section of a lower side surface of an intake port which is adjacent to a pre-compression chamber of a cylinder. This protruding edge portion serves to deflect air-fuel mixture introduced into the pre-compression chamber through the intake port so as to direct it to a bearing portion provided between a piston and a connecting rod. Further, a cut-in groove is formed in the protruding edge section and is adapted to allow any liquid remaining in the intake port to flow into the pre-comparison chamber.

Abstract: The present invention relates to an internal combustion engine cylinder assembly comprising a first cylinder having substantially vertically disposed interior walls defining a firing chamber therein; first piston means housed within the firing chamber and adapted for vertical reciprocation within the firing chamber; gas inlet channels means in the lower portion of the firing chamber; a crankcase housing having a gas compression chamber disposed therein; valve means adapted to permit fresh air mixture to be charged into the gas compression chamber upon the depressuring of the chamber; fuel introduction means for introducing liquid fuel into the upper portion of the firing chamber; second cylinder means positioned at the upper end of the first cylinder and having an exhaust chamber therein and a second piston means disposed within the exhaust chamber and adapted for vertical reciprocation therein, the exhaust chamber communicating with the upper end of the firing chamber; the second cylinder means being provide

Abstract: The present invention relates to an internal combustion engine cylinder assembly comprising a cylinder having substantially vertically disposed interior walls defining a firing chamber therein; piston means housed within the firing chamber and adapted for vertical reciprocation within the firing chamber; gas inlet channels in the lower portion of the firing chamber; a crankcase housing having a gas compression chamber disposed therein; valve means adapted for passing air into the gas compression chamber upon the depressuring thereof; cylinder closure means positioned at the upper end of the cylinder defining the upper end of the firing chamber and being provided with exhaust gas valve means, adapted for cyclic opening and closing to alternatively permit the removal of exhaust gases from the firing chamber and the pressuring of fresh fuel/air mixtures in the firing chamber; fuel introduction means for introducing fuel into the upper portion of the firing chamber; fuel ignition means for igniting a compressed f

Abstract: A combustion chamber and scavenging configuration for a two-cycle internal combustion engine. The combustion chamber is comprised of an offset recess surrounded by a squish area. An exhaust port is formed on the side of the cylinder opposite to the area where the recess is offset while the intake or transfer ports are disposed on the side to which the recess is offset. The transfer or scavenge ports are configured so as to open progressively first diametrically opposite to the exhaust port and then in an area extending around the area toward the exhaust port.

Abstract: Disclosed is a two-stroke engine having a central scavenging system through which the scavenging mixture, regulated into a single stream at a scavenging port provided in the top wall of the piston, jets upwardly into the center of the top portion of the cylinder bore and then spreads radially outwards so as to provide a plurality of currents of scavenging mixture. These currents branch from the main stream of scavenging mixture and flow through shorter distance as well as undergo similar flow environment with respect to one another due to symmetry in regard to the center of the cylinder. Thus, the scavenging performance of the two-stroke engine can be greatly improved.

Abstract: A polystyrene foam pattern (10) is provided for the cylinder block of a crankcase compression two-cycle engine having transfer passages (15) formed in the block. The pattern includes a head-end component (12) and a crankcase end component (11) mating with each other. The mating surfaces extend through the transfer ports (14), transfer passages (15), and exhaust ports (16) to allow the formation of complex passages with die cast pattern components.

Abstract: A two-cycle internal combustion engine with a transfer pressure plate affixed to the intake passage, the transfer port pressure plate has a central aperture with a plurality of jets directed into that central aperture area, the jets being fed by a conduit connected to the crankcase of the internal combustion engine.

Abstract: In a two cycle internal combustion engine (2), a fuel-air flow passage and reservoir (52) is provided along the exhaust bridge (34) and between the piston (4) and the cylinder inner wall (36) for lubricating the exhaust bridge (34). The piston (4) has a flat spot (50) machined on its side wall (38) to form an axially extending flow passage and reservoir closed at its top end by the piston rings (40) and at its bottom end by a lower portion (60) of the piston side wall (38) which is not machined and which is closely adjacent the cylinder inner wall (36). When the piston (4) is in its power stroke, crankcase pressure forces fuel-air mixture through holes (56, 58) in the piston side wall (38) at the flat surface (50) into the flow passage and reservoir (52). If the exhaust bridge (34) heats and expands into the cylinder (6), the piston (4) will not rub on it.

Abstract: In a two cycle internal combustion engine (2) having a cylinder liner (14), a fuel-air flow passage (52) is provided from the crankcase (8) to the exhaust bridge (38) in the cylinder liner (14) and the exhaust bridge (39) in the cylinder block (12) along the interface between the cylinder liner (14) and the cylinder block (12). A plurality of apertures (57-60) are provided through the cylinder liner (14) communicating with the fuel-air flow passage (52). A second fuel-air flow passage (56) is provided between the piston (4) and the cylinder liner (14) and in communication with the apertures (57-60) to facilitate fuel-air mixture flow through the exhaust bridge (38) to improve lubrication and cooling thereof.

Abstract: It is a reciprocating type of internal combustion engine, of which the inside of piston is furnished with a gasifying chamber; the outlet of the gasifying chamber can, during the piston moving reciprocatingly, be in alignment with the spraying nozzle on the cylinder and the third scavenging passage in sequence so as to let the spraying nozzle directly spray fuel into the gasifying chamber, and to let the fuel absorb the high temperature heat of the piston top to cause the fuel to be gasified completely. The gasified fuel flows into the third scavenging passage during the piston moving downwards and is to be stored therein temporarily; then, the gasified fuel is compressed into the cylinder by means of the compressed air in the crankcase so as to mix with the fresh air entered into the cylinder via other scavenging passages. The gas mixture is to be compressed with the upward moving piston, and to be exploded to generate a mechanical power.

Abstract: Several embodiments of arrangements for blowing condensation from a horizontally extending portion of a transfer passage of a two-cycle internal combustion engine into the combustion chamber for improving stability of running, particularly under idle, low speed, acceleration and deceleration conditions.

Abstract: An internal combustion engine cylinder assembly comprising a first elongated cylinder having substantially vertically disposed interior walls defining an elongated firing chamber therein; first piston means housed within the firing chamber and adapted for vertical reciprocation within the firing chamber; gas inlet channels means in the lower portion of the firing chamber; a crankcase housing having a gas compression chamber disposed therein; valve means adapted to permit fresh fuel/air mixtures to be charged into the gas compression chamber upon the depressuring of the chamber; second cylinder means positioned at the upper end of the first cylinder and having an exhaust chamber therein and a second piston means disposed within the exhaust chamber and adapted for vertical reciprocation therein, the exhaust chamber communicating with the upper end of the firing chamber; the second cylinder means being provided in the lower portion thereof with at least one exhaust gas port adapted for cyclic opening and closing

Abstract: An internal combustion engine cylinder assembly comprising an elongated cylinder having substantially vertically disposed interior walls defining an elongated firing chamber therein; piston means housed within the firing chamber and adapted for vertical reciprocation within the firing chamber; gas inlet channels in the lower portion of the firing chamber; a crankcase housing having a gas compression chamber disposed therein; a reed valve means pivotally secured to the inner walls of the gas compression chamber and adapted for passing fuel/air mixtures into the gas compression chamber upon the depressuring thereof; a cylinder closure means positioned at the upper end of the cylinder defining the upper end of the firing chamber and being provided with exhaust gas valve means, adapted for cyclic opening and closing to alternatively permit the removal of exhaust gases from the firing chamber and the pressuring to the fresh fuel/air mixtures in the firing chamber; fuel ignition means for igniting a compressed fuel

Abstract: A two-cycle internal combustion engine having an oblong cylinder and an oblong piston therein. The engine includes two sets of scavenging ports at either end of the oblong cylinder having at least three ports each. Scavenging passages extending to the scavenging ports may be directed at sequentially increasing angles of inclination to the local normal with the cylinder away from the exhaust porting. In this way, flow may be directed across the piston head away from the exhaust porting and then upwardly to return toward the exhaust porting. A domed piston is also disclosed having discrete guide surfaces on the domed surface of the piston to specifically direct incoming air/fuel mixture upwardly from each of the scavenging ports. An element of the cylinder midway in the long dimension of the cylinder extends in the direction of piston movement without porting so as to provide a smooth wall surface.

Abstract: The two-cycle internal combustion engine has a crankcase, a combustion chamber including an exhaust port, a fuel intake port and a pair of air-intake ports located on the opposite sides of the fuel intake port, and a piston movable relative to the combustion chamber between top dead center and bottom dead center positions. The crankcase has separate air and fuel inlets and includes interior portions defining an air crankcase portion which communicates with the crankcase air inlet and with two air transfer passages which communicated with the air intake ports and a separate fuel crankcase portion which communicates with the crankcase fuel inlet and a fuel transfer passage which communicates with the fuel intake port. Air is drawn through the crankcase air inlet into the air crankcase portion and a fuel-air mixture is drawn through the crankcase fuel inlet into the fuel crankcase portion during the upstroke of the piston toward top dead center.

Abstract: The internal combustion engine has, arranged in pairs, cylinders offset in angle in relation to one another in the direction of the axis of rotation of its crankshaft. The engine block consists of two castings, each of which combines integrally in one piece with one another one half of a crankcase, one of the cylinder housings of each pair and the cylinder heads. The castings are symmetrical in rotation at 180.degree. in relation to an axis of symmetry lying in the plane of separation of the crankcase perpendicularly of the axis of rotation of the crankshaft, so that they can be manufactured in one and the same casting mold. The cranks for the crankshaft which are allocated to each piston pair are connected with one another through a cranked middle piece, to reduce the distance between the cylinder axes and thus to reduce vibration.

Abstract: Horsepower and fuel economy improvements, and a reduction in horsepower variation, are realized in a two cycle loop scavenged internal combustion engine by enhancing combustion chamber (10) intake directional flow (28) by directing flow along the outermost portions (54) of the transfer passages (12), and blocking flow along shorter paths (56) adjacent the cylinder (6) which otherwise short-circuit the outermost flow and adversely affect directional flow into the combustion chamber from the intake ports (16), to substantially eliminate intake flow directed toward the exhaust port (26) from the intake port otherwise caused by the short-circuiting. The intake port flow in the combustion chamber is afforded in a direction determined by the non-short-circuited path in the transfer passage, and the direction-altering flow in the combustion chamber from the intake port otherwise due to the short-circuit path is substantially eliminated.

Abstract: An improved combustion chamber configuration for a two-cycle engine that improves combustion and running at both idle and high speed. The combustion chamber comprises a first portion that communicates with a spark plug and has a relatively small volume. The first portion communicates with a second larger volume portion that has a decreasing cross-sectional area as approaching the exhaust port so as to insure complete flame propagation even at high engine speeds.

Abstract: The two-cycle internal combustion engine includes an engine block having a cylindrical wall defining a cylinder having a head end, a piston mounted for reciprocative movement in the cylinder, and a passage in the engine block, such as an exhaust passage, a transfer passage, or a crankcase fuel intake passage, terminating at the cylinder wall in a port, such as an exhaust port, a transfer port or a piston-controlled, crankcase fuel intake port, having upper and lower edges. A valve mounted in the passage for movement relative to the port is operable to selectively vary the effective distance of one of the port edges from the cylinder head end and thereby provide the capability of varying the timing of the port opening and/or closing as required to obtain optimum engine performance at different operating conditions.

Abstract: A two-cycle internal combustion engine having reed valves in the fuel/air supply system is provided with an element in the flow path of the fuel/air into the reed valves, which element is shaped and positioned to promote uniformity of flow of the fuel/air mixture in the flow passage.

Abstract: A 2-stroke engine having a combustion chamber and a scavenge port which is open to the combustion chamber. When the engine is operating under a light load in which a large amount of unburned components, incompletely burned components and oxygen remains in the combustion chamber, fresh air is fed into the combustion chamber from the scavenge port at a low speed so that the fresh air does not disturb the residual gas in the combustion chamber. As a result of this, oxidation of the unburned components and the incompletely burned components continues without interruption during the expansion stroke and the compression stroke and causes self-ignition of the residual gas at the end of the compression stroke. The self-ignited residual gas causes ignition of the fuel injected into the combustion chamber from a fuel injector.

Abstract: A porting and scavenging system for a two-cycle internal combustion engine that permits a more compact arrangement. The engine employs scavenging passages that lie on opposite sides of a plane passing through the cylinder axis and the center of the exhaust ports. These scavenging passages are arcuate in cross-sections perpendicular to the cylinder axis and their centers lie on the plane but are offset from the cylinder axis to the side opposite the exhaust ports. In addition, the scavenge passages extend at an angle to the cylinder axis so that their outlets into the cylinders disposed further from the exhaust ports than their inlets from the crankcase. This arrangement not only improves compactness but significantly improves scavenging.

Abstract: Two-cycle internal combustion engines are disclosed incorporating intake and transfer ports and passages, and including intake porting at the sides of the cylinder in the regions of an axial plane through the cylinder containing the axis of the wrist pin interconnecting the piston with the crank.

Abstract: Two-cycle internal combustion engines are disclosed incorporating intake and transfer ports and passages, and including passages means in the cylinder wall interconnecting the intake tract and a transfer passage in a region above the piston when the piston is in bottom dead center position.

Abstract: A two cycle engine having piston controlled inlet and exhaust ports is provided with a secondary one-way valved air fuel mixture passage to the combustion chamber adjacent the spark plug.

Abstract: An internal combustion engine comprises a combustion chamber and a piston movable relative to the combustion chamber between top dead center and bottom dead center positions. A fuel transfer passage introduces fuel-air mixture into the combustion chamber in response to piston movement. An auxiliary chamber is also provided which is communicable with the combustion chamber in response to piston movement shortly after the ignition of a fuel-air mixture, such that high pressure ignition gases enter the auxiliary chamber. The high pressure ignition gases thereafter flow back into the combustion chamber in response to piston movement before communication chamber in response to piston movement before communication is established between the combustion chamber and the fuel transfer passage. The incoming flow of high pressure ignition gases serves to influence the normal scavenging streams.

Abstract: In a two-stroke internal combustion piston engine, a piston is reciprocally movable within an axially elongated cylinder. The piston has a bottom dead center position and in the region of this position, the cylinder has an exhaust opening and a number of pairs of scavenging openings. An axially extending plane within the cylinder divides the exhaust opening in half and in each pair the scavenging openings are arranged symmetrically on opposite sides of the axially extending plane. Each pair of scavenging openings is located at a different distance from the exhaust opening. The projection of the side surfaces of the pairs of scavenging openings extending in the axial direction of the cylinder each form a different angle at the point of intersection of the projections and the point of intersection is directed away from the exhaust opening.

Abstract: The invention provides an internal combustion engine comprising a cylinder block having therein a bore and first, second and third openings each communicating with the bore. A cover member having therein first and second cavities is removably attachable on the cylinder block with the first cavity communicating with the first bore opening and the second cavity communicating with each of the second and third bore openings. The cover member cavities and the associated bore openings together form passages communicating with the bore.

Abstract: A two stroke cycle internal combustion engine having a closed crankcase adapted to receive a air-fuel mixture and a cylinder extending from said crankcase,a piston reciprocally movable in said cylinder which alternately produces a low pressure condition in said crankcase as it approaches top dead center and a high pressure condition in said cylinder as it approaches bottom dead center,a fuel reservoir for supplying liquid fuel to the air fuel mixture in said crankcase, a bypass passage connecting said crankcase to said cylinder,and a conduit connecting said crankcase to the fuel reservoir for pumping fuel accumulated in said crankcase during starting into said reservoir, and a unidirectional flow control device in said conduit for preventing return flow from said reservoir to said crankcase.

Abstract: A two cycle engine has a cylinder, a piston axially slidably mounted in said cylinder, and through the wall of the cylinder an intake port, exhaust port, and scavenging port. These ports are respectively connected to intake, exhaust, and scavenging passages. An auxiliary intake passage opens through the cylinder wall, circumferentially spaced from the other intake passage so as to leave an axially-extending side-support surface to permit of an enlarged total intake port area without permitting the piston to tilt or otherwise wander from its true path, thereby to reduce piston clatter and wear, and to improve engine performance.

Abstract: An internal combustion engine comprises a combustion chamber and a piston movable relative to the combustion chamber between top dead center and bottom dead center positions. A fuel transfer passage introduces fuel-air mixture into the combustion chamber in response to piston movement. An auxiliary chamber is also provided which is communicable with the combustion chamber in response to piston movement shortly after the ignition of a fuel-air mixture, such that high pressure ignition gases enter the auxiliary chamber. The high pressure ignition gases thereafter flow back into the combustion chamber in response to piston movement before communication is established between the combustion chamber and the fuel transfer passage. The incoming flow of high pressure ignition gases serves to influence the normal scavenging streams.

Abstract: A two-cycle engine (10) has an idle fuel system which admits fuel-air mixture into the transfer passages (22). Heated air is supplied to the idle mixing passage (42) by a serpentine air passage (45), while fuel from the carburetor float bowl (33) is supplied through a needle valve (50). A reed valve (43) admits the idle mixture to the transfer passage (22).

Abstract: An in-line, multi-cylinder, two-cycle loop charged engine 10 has transfer passages 21, 22, and 23 partially formed by cavities die-cast in the cylinder block 14. The transfer passages are completed by covers, 24 and 25 bolted to the block 14. An efficient loop charging system is thus provided in a completely die-cast cylinder block.

Abstract: A transfer duct construction for a two-stroke engine cylinder in which a transfer port in the cylinder wall has a side wall that is perpendicular to the parting line along which the cylinder is cast; a transfer port cover extends over the transfer port and includes an inner end wall having an inclined surface positioned adjacent the perpendicular side wall of the port to direct a fresh fuel-air charge away from an exhaust port.

Abstract: A two cycle internal combustion engine with improved cylinder scavenging. The described engine embodiment is a baffled piston two cycle internal combustion engine whose power is substantially increased by directing fuel mixture in the normally spent gas filled region behind the piston baffle during each intake-exhaust portion of the engine cycles to scavenge spent gas from this region and increase the total volume of fuel mixture in the cylinder at the time of ignition. According to the preferred practice of the invention a portion of the fuel mixture displaced from the engine crankcase to the cylinder intake port or ports is diverted to auxiliary ports in the cylinder wall which direct the mixture against the rear side of the piston baffle to effect through scavenging of the region directly behind the baffle.

Abstract: A two-stoke cycle combustion-engine with crank-chamber compression is described, free of charging transfer passages external to the cylinder, with pumping-displacement exceeding working-displacement for responsive intake and thorough scavenging of spent-gas residue, and featuring an annular water-cooled cell, suspended from the cylinder-head by several water-conduits, and cooperating with an annular recess in the piston-head so as to form, and transversely separate, a plain working-chamber and an annular working-chamber, longitudinally scavengeable in series, bottom-to-top and top-to-bottom, respectively, with minimal loss of charge to exhaust-port, such a system of scavenging also reducing piston cooling-problems and misfiring associated with charge-dilution (in gasoline-engines operating under partial-charge conditions). In addition, a more general scavenging principle is enunciated and claimed, applicable to rear-compression and separately-scavenged two-stroke engines.

Abstract: Two-cycle internal combustion engines are disclosed incorporating intake and transfer ports and passages, and including passages means in the cylinder wall interconnecting the intake tract and a transfer passage in a region above the piston when the piston is in bottom dead center position.

Abstract: A two-cycle engine of the crank chamber preloading type of the construction in which a crankcase, a cylinder head and a cylinder are clamped together by a plurality of clamping members penetrating the cylinder includes a suction port formed in a wall of the cylinder, an exhaust port formed on a side of the cylinder opposite the suction port, at least one main scavenging port disposed between the suction port and the exhaust port and directed toward the suction port, and at least one ancillary scavenging port disposed above the suction port and juxtaposed against the exhaust port. At least one ancillary scavenging passage branching from at least one main scavenging passage and communicating with the ancillary scavenging port extends around an opening for one of clamping members on the suction side.

Abstract: An internal combustion engine comprises a combustion chamber and a crankcase which extends from the combustion chamber. A primary fuel delivery system introduces fuel from a fuel source into the combustion chamber, and a primer fuel delivery system is selectively operable for introducing fuel from the source into the combustion chamber in addition to fuel which is introduced by the primary fuel delivery system. A collector assembly communicates with the crankcase for accumulating residual fuel from the crankcase, and a residual fuel delivery system supplies fuel from the collector assembly into the combustion chamber. A control valve mechanism is connected to the primer fuel delivery system and the residual fuel delivery system for blocking the supply of fuel by the residual fuel delivery system during operation of the primer fuel delivery system.

Abstract: The rotating combustible mixture in the crankcase of a two-cycle gasoline engine is scooped into the transfer duct leading to the cylinder by a plurality of vanes extending over the crankcase flywheel and in close juxtaposition thereto.

Abstract: A two-cycle internal combustion engine includes a cylinder, a piston in the cylinder and a crankcase pump. The crankcase pump is divided into a first chamber and a second chamber by a membrane. At least one respective transfer passage connects each of the respective chambers to the cylinder. Inlets are provided for admitting pure air into the first chamber and for admitting carbureted air into the second chamber. Devices are provided for opening that one of the transfer passages communicating between the cylinder and the first chamber first and thereafter for opening the one of the transfer passages communicating between said cylinder and said second chamber during operation of the engine.

Abstract: A 2-cycle engine having a transfer passage communicating the crank room with the combustion chamber. An accumulation tank having a volume which is larger than the stroke volume of the piston is arranged in the transfer passage. A reed valve is arranged in the transfer passage between the crank room and the accumulation tank.

Abstract: A 2-cycle engine having a transfer passage communicating the crank case with the combustion chamber. The transfer passage comprises a first passage and a second passage. The first passage has a long length and a small cross-sectional area for causing a fresh combustible mixture to flow at a high speed. The second passage has a short length and a large cross-sectional area for causing a fresh combustible mixture to flow at a low speed. An exhaust gas recirculation device is provided for recirculating the exhaust gas from the exhaust system into the intake system of the engine.

Abstract: A 2-cycle engine having a transfer passage communicating the crank case with the combustion chamber. The transfer passage comprises a first passage and a second passage. The first passage has a long length and a small cross-sectional area for causing a fresh combustible mixture to flow at a high speed. The second passage has a short length and a large cross-sectional area for causing a fresh combustible mixture to flow at a low speed. The second passage is connected to the crank room via the bypass passage. A normally closed valve is arranged in the bypass passage. The valve is opened when the engine is operating under a heavy load.

Abstract: In the engine the side wall of the piston is provided with a perforation at a portion not facing an exhaust port of the cylinder for communicating the cylinder wall with the crankcase chamber.

Abstract: Disclosed is a 2-cycle engine having a scavenging passage communicating the crank case with the combustion chamber. The scavenging passage comprises a first passage and a second passage. The first passage has a long length and a small cross-sectional area for causing a fresh combustible mixture to flow at a high speed. The second passage has a short length and a large cross-sectional area for causing a fresh combustible mixture to flow at a low speed. The vaporization of the fresh combustible mixture is prometed in the first passage and, in addition, the fresh combustible mixture flows into the combustion chamber at a low speed. As a result of this, an active thermoatmosphere combustion is caused in the combustion chamber.

Abstract: In operation of an internal combustion engine, a lamina of air is introduced into the combustion chamber to line the wall thereof, the fuel being admitted into the interior of the lamina of air. In a two-stroke engine, air entering the combustion chamber is driven by the incoming fuel mixture to form a lamina which lines the wall of the combustion chamber.

Abstract: A two cycle loop scavenging engine of the crankcase precompression type having a pair of equally dimensioned scavenging passages 14, 16 disposed in a cylinder block 10 behind an apertured cylinder line 12. The passages are symmetrically positioned on opposite sides of a vertical plane A including the cylinder axis and oriented at an angle .theta. to a plane normal to the crankshaft 17. Recessed notches 22, 23 in the lower periphery of the piston skirt 20a mate with notches 12e, 12f, respectively, in the bottom of the cylinder liner at the entrances to scavenging passages 14, 16 at the bottom of each piston stroke. The notches 22, 23 have unequal cross-sectional areas to compensate for unequal fuel mixture pressures at the scavenging passage entrances caused by the rotation of the crankweb 17a, thereby producing a more uniform fuel mixture distribution in the cylinder.

Abstract: A two-cycle internal combustion engine having reed-type intake valving, and specially configured and positioned intake and injector porting, with the porting constructed and arranged to improve various of the operating characteristics of the engine, and particularly adapted to increase the effectiveness of the injection through the injector porting.

Abstract: A piston and cylinder for two-cycle engines wherein the fuel-air mixture is precompressed in the crankcase and flows to the combustion chamber through transfer passages formed in the cylinder wall and under the control of the piston movement. The piston skirt is formed with windows or openings adjacent the end faces of the piston pin, the latter being mounted in piston pin bosses carried by bearing brackets depending from the piston head and, when the piston is at its lower dead center, the windows or openings register with the inlet openings of the transfer passages so that the precompressed fuel-air mixture then flows through the interior of the piston, the openings in the piston skirt and the transfer passages and into the combustion chamber itself which contains a depression volume.