Abstract: Several embodiments of the type two-cycle crankcase compression engines having exhaust control valves for controlling the effective compression ratio of the engine. The exhaust control valves are rotatably journaled in respective cylinder banks and are disposed at the same distance from a plane passing through the center of the valley between the cylinder banks as each other facilitating a common drive therefor. In one embodiment the exhaust control valves are disposed on the side of the cylinder banks adjacent the valley and in another embodiment they are disposed on the outside of the cylinder banks.

Abstract: A variable exhaust resonance chamber valve system for internal combustion engine. The engine includes a cylinder having an exhaust port with an axial extent along the axis of the cylinder structure. An exhaust passage having a resonance port extends from the exhaust port to exhaust the engine. A resonance chamber extends from the resonance port and communicates with the exhaust passage through the resonance port. A port valve is adjustable between a second position, in which the port valve exposes the exhaust port throughout its axial extent and occludes the resonance port, and a first position, in which the port valve restricts the axial extent of the exhaust port and exposes the resonance port. A valve control module is connected to the port valve and functions to adjust the port valve between first and second positions in response to engine conditions. At low speeds and low output conditions, the valve is in its first position.

Abstract: A loop scavenge two-cycle internal combustion engine that includes a partial wall partition disposed between a scavenging path and a cylinder bore, with a cooling port formed in the partial wall partition for enabling fresh gas in the scavenging path to contact directly with a peripheral wall of a piston in the cylinder. The fresh gas in the scavenging path directly contacts and efficiently cools the peripheral surface of the piston to prevent heat rise and distortion within the engine. The partial wall partition and cooling port maximize both cooling efficiently and cylinder strength and durability.

Abstract: The present invention relates to operation processes of two-stroke engines. A two-stroke engine uses a slide valve (10) so that the inlet-outlet passage (9) connected to the exhaust manifold (18) may be connected to the inlet pipe after the outlet of exhaust gases from the cylinder (4). A fresh load is then introduced into the cylinder (4) simultaneously through a scavenging port (6) connected to the crankshaft chamber (2) by a scavenging passage, and through an inlet-outlet port (8) connected to the inlet pipe. The crankshaft chamber (2) is filled when the piston (5) moves from the bottom dead center after the port (8) is opened at its lower edge. Practically continuous feeding of fresh loads into a single-cylinder engine can thus be achieved. The increase in the time-section ration of the gas distribution organs ensures maximum filling of the cylinder (4) while reducing the time therefor and the losses to a minimum.

Abstract: To provide a compact two-cylinder engine in which adjacent cylinders are located close to each other. In the two-cycle engine of the present invention, the scavenging passages of scavenging ports adjacent to the exhaust ports are flat or elongate in their cross section and extend to the sides of the exhaust ports. This structure allows the cross-sectional area of the scavenging passages to be sufficient, but allows the width of the cylinder section between adjacent cylinders to be decreased. Furthermore, in the two-cycle engine of the present invention, the exhaust passages of the cylinders are arranged in the direction substantially orthogonal with the direction of alignment of the cylinders, and the exhaust control valves are positioned near the exhaust ports in order to control an opening amount of the exhaust ports.

Abstract: A number of embodiments of two cycle crankcase compression internal combustion engines having at least two cylinders in a common bank in side-by-side relationship. Each embodiment incorporates a main Schnurle type scavenging system that includes a pair of main scavenge passages on opposite sides of the exhaust passage that terminate in main scavenge ports that are disposed in proximity to and on opposite sides of the exhaust port. A transversely extending supplemental scavenge passage is provided for delivering a charge to the combustion chamber to somewhat restrict the scavenging flow so as to prevent fuel from passing out of the exhaust port. Fuel is injected into proximity with this supplemental scavenge passage. This facilitates stratification of the fuel charge. The ports are rotated from normal around the cylinder bore axis in many embodiments to provide a more compact construction.

Abstract: An exhaust valve holder including accommodations for additional sealing and resistance to movement. This includes a groove wide enough for two sealing o-rings, a groove or slot which does not run the circumference of the holder and binds against a tab of a holder plate to resist rotational movement and a one piece design.

Abstract: Cylinder (1) for a two-stroke combustion engine intended for a handheld working tool, preferrably a chain saw. The exhaust port's (3) mouth (17) inside the cylinder as well as the cylinder's transfer ports (5, 6, 7, 8) are arranged symmetrically around a common symmetry plane (9) which follows the cylinder's symmetry axis (10). At the exhaust port's (3) mouth (11) on the outside of the cylinder a fastening plane (12) with fastening holes (13) is embodied for a directly mounted muffler, and the fastening plane (12) is essentially perpendicular to the symmetry plane (9), and the exhaust port is angled sideways in relation to the symmetry plane (9) and its mouth (11) is shifted sideways in relation to the symmetry plane (9).

Abstract: A number of embodiments of two cycle crankcase compression internal combustion engines having at least two cylinders in a common bank in side-by-side relationship. Each embodiment incorporates a main Schnurle type scavenging system that includes a pair of main scavenge passages on opposite sides of the exhaust passage that terminate in main scavenge ports that are disposed in proximity to and on opposite sides of the exhaust port. A transversely extending supplemental scavenge passage is provided for delivering a charge to the combustion chamber to somewhat restrict the scavenging flow so as to prevent fuel from passing out of the exhaust port. Fuel is injected into proximity with this supplemental scavenge passage. This facilitates stratification of the fuel charge. The ports are rotated from normal around the cylinder bore axis in many embodiments to provide a more compact construction.

Abstract: A control valve is disposed in a communication passage for communication between a combustion chamber and a chamber portion adjacent to the combustion chamber, and through the communication passage at least one of a fuel and an air-fuel mixture, and a highly compressed gas, are supplied or charged into the combustion chamber and the chamber portion adjacent thereto, respectively. The control valve includes a first control valve disposed in the first communication passage and a second control valve disposed in the second communication passage, the first control valve causes the first communication passage to open at a timing near closing of an exhaust port and causes it to close halfway in a compression stroke. The second control valve causes the second communication passage to open at a timing near closing of the scavenging ports and causes it to close prior to closing of the first communication passage.

Abstract: A two-cycle internal combustion engine comprising a combustion chamber, an exhaust port and a scavenging port each opening into the combustion chamber. The opening area of each of the exhaust port and the scavenging port is made as small as possible in relation to the engine displacement so as to restrict the revolutions of the engine crank shaft during a rated output operation of the engine. The width in the lateral direction of the opening of the exhaust port corresponds to an angle of 60.degree. as measured from the center of the combustion chamber, and the width in the lateral direction of the opening of the scavenging port corresponds to an angle of 32.degree. as measured from the center of the combustion chamber.

Abstract: According to the invention, the valve comprises a cylindrical body (21) in a housing (21), for receiving one end of a return spring while the end is in contact with the case. The valve also includes two ribs (22, 23) for connection to a sealing plate (25) contacting the inner surface of an annular chamber (27) above an opening (26) thereof. The annular chamber is arranged to shorten the distance between the valve and the corresponding transfer port. The air valve of the invention is for spark ignition engines, in particular two-stroke engines.

Abstract: A two-stroke internal combustion engine for a hand-guided working tool has a cylinder with a cylinder wall and a piston reciprocating in the cylinder and defining a combustion chamber with the cylinder wall. Transfer parts, each having an outlet window, for introducing combustion air and fuel into the combustion chamber are provided. The outlet windows are cut into the cylinder wall for connecting the transfer parts to the combustion chamber. The outlet windows have limiting edges extending parallel to a central cylinder axis of the cylinder and are located within an inner mantle surface of the cylinder wall. The outlet windows have a window width measured in a circumferential direction of the inner mantle surface. The transfer parts have a channel width measured in the circumferential direction of the inner mantle surface, whereby the window width is greater than the channel width. The transfer parts have a transition portion into the outlet windows.

Abstract: A two-cycle engine having a plurality of combustion chambers, each chamber in communication with an air/fuel mixture delivery passage via a crankcase chamber, is disclosed. The engine includes a system for delivering fuel which precipitates out of the air/fuel mixture within the delivery passage to the combustion chambers. The system includes at least one fuel catch in the form of a trough positioned in each delivery passage and a fuel delivery passage extending from the catch to the combustion chamber.

Abstract: A two-stroke internal combustion engine in a working machine such as a chain saw has been prone to stalling when the stance of the machine was changed from slanting down to slanting up. Such stalling is minimized when lower longitudinal scavenging passage in the cylinder block of the engine have smaller cross section as compared with upper scavenging passage, and when the crank chamber of the engine includes a flow restricting portion for impeding the flow of liquid fuel into the lower scavenging passage when the stance is changed. The engine has a cylinder block (12), a crankcase (20), scavenging passages (27, 27), and a flow restricting portion (40) on an inner peripheral surface (22a) of the crank chamber (22).

Abstract: A number of embodiments of two-cycle engines employing Schnurle-type scavenging. In addition, a tumble port is also incorporated so as to introduce a tumble charge into the combustion chamber and reduce the likelihood of fresh charge from exiting from the exhaust port. This tumble charge may be utilized to achieve stratification, and the fuel charge may be delivered to the combustion chamber through the tumble port or in proximity to it. Also, arrangements are shown for controlling the amount of tumble flow.

Abstract: In a two cycle internal combustion engine with uni-directional flow scavenging wherein a piston is disposed in a cylinder so as to be movable between top and bottom dead center end positions, the cylinder has fresh air inlet passages which are so arranged that their bottom walls are disposed below the piston top edge when the piston is in its bottom dead center position so that part of the piston top land is directly exposed to the fresh air flow through the air inlet passages and oil discharge bores extend from the air inlet passages and are in communication with the oil circulating system for the removal of oil wiped off the cylinder wall and collected in the inlet passages.

Abstract: A two stroke engine (10) has an exhaust port (16) extending from a side wall of a cylinder (12). A plate valve (26) is movable to an extended position where is the plate valve blocks the upper edge (54) of the exhaust port 16 to effectively retard the opening of the exhaust valve and retractable to a second position which provides the entire axial extent of the exhaust port (16) to be openable with respect to the cylinder. The position of the plate valve (26) is controlled by a diaphragm bladder (46) which is responsive to pressure in the intake system (19) that is in communication with the bladder (46) via an inlet passage (48).

Abstract: An engine having an engine block defining at least two cylinders having respective cylinder heads. Pistons are reciprocal within respective ones of the cylinders. The cylinders have respective fuel inlet ports and exhaust ports and two of said cylinders have an idle relief port disposed between their respective exhaust port and head ends. The idle relief ports of the cylinders are interconnected by a passageway for providing communication between the idle relief ports of said at least two cylinders. This has been found to provide reduced pull start resistance, reduced engine vibration during idle, and significantly reduced horsepower loss over a wide operating range which horsepower loss is normally associated with idle prior art relief structures which vent directly from idle relief ports to atmosphere.

Abstract: A two-cycle internal combustion engine is provided which comprises: a cylinder receiving a reciprocative piston and having a top portion provided with a combustion chamber in which a spark plug faces; an exhaust port laterally opening into the cylinder; at least one first scavenging port opening into the cylinder at one side of the exhaust port; and at least one second scavenging port opening into the cylinder at another side of the exhaust port opposite to said one side. Each of the first and second scavenging ports directs scavenging gas away from the exhaust port. The first scavenging port opens into the cylinder with an upward inclination for directing a first portion of the scavenging gas upwardly toward the top portion of the cylinder, whereas the second scavenging port is oriented to direct a second portion of the scavenging gas transversely of the cylinder toward a wall portion of the cylinder where the first scavenging port is formed.

Abstract: A multi-cylinder two-stroke cycle engine according to the invention incorporates a plurality of cylinders (1,2,3) arranged in line with each cylinder having at least two inlet ports one on each of the two opposite longitudinal sides of the in-line cylinders (1,2,3). Air passages (67,77) extend along said opposite sides to supply air from a supercharger (not shown) to the respective inlet ports. An air control valve (68) is operable to selectively control air supply to one or both of said air passages (67,77) whereby optimum combustion conditions are obtained for various engine load/speed conditions. A centrifugal supercharger arrangement is also disclosed, the supercharger being coupled to the engine crankshaft and interposed between the cylinder block and the engine flywheel.

Abstract: A cylinder for a two-cycle internal combustion engine is disclosed which enables reduction of HC in exhaust gas to be effectively attained without any complicated modification. A pair of scavenging ports 20, 20 are oppositely formed which employ loop scavenging mode towards the direction opposite to an exhaust port 16 symmetrically with respect to the longitudinal section F bisecting the exhaust port 16. A pocket portion 20c is formed at the innermost end of the inner surface 20a of the end portion closer to the exhaust port 16 of each of the scavenging ports 20, 20 to form a prolonged wall portion 20d extending along the inner wall surface 5 of the cylinder 1 in the direction apart from the exhaust port 16.

Abstract: A two stroke engine having a variable inlet port timing device in conjunction with a piston port controlled timing apparatus for filling the top of transfer passages, that connect the crankcase chamber to the combustion chamber of the engine, with buffer gas such as exhaust gas or secondary air for the reduction of pollutants, improvement of performance, and delivery ratio of an internal combustion two-stroke engine and the like. Piston port controlled timing is provided by buffer air passages having a movable portion with inlet and outlet ports disposed through the piston. In another embodiment piston controlled selective exhaust gas recirculation is provided and a rotary valve in the exhaust gas recirculation passage is fitted to improve the performance of the engine. The pressure in the crankcase may be controlled by a rotary valve comprises a pair of rotary disc plates.

Abstract: Embodiments of the scavenge passages and the scavenge ports for a two cycle crankcase compression engine wherein the scavenge ports have their side edges tapered outwardly to facilitate the flow into the cylinder block.

Abstract: A two-stroke engine which includes a cylinder in which a piston moves with a device being provided for allowing the feeding of a charge under pressure to the cylinder and at least two inlet ports in a well of the cylinder. The engine includes a device for selectively sealing a section of flow of the inlet port in accordance with at least one working parameter of the engine The device for selectively sealing may, for example, include a rotary plug placed opposite the inlet ports, with the plug including at least two through openings.

Abstract: An improved scavenging system for a two cycle internal combustion engine wherein the cylinder block of the engine is provided with an internal plenum chamber that surrounds the lower portion of the cylinders and which supplies the scavenge ports of the engine. In this way, it will be ensured that the proper air flow can issue from each scavenge port.

Abstract: A number of embodiments of scavenging port configurations for two-cycle internal combustion engines wherein the a scavenge port is formed adjacent the exhaust port and is masked by a cylinder liner so as to avoid the escape of scavenging gases to the exhaust port, particularly at the end of the scavenging cycle.

Abstract: A number of embodiments of outboard motors embodying pressure scavenged 2-cycle internal combustion engines. In each embodiment, a plenum chamber serves the scavenge passages of the engine and the pressure relief for a scavenge pump is provided by a pressure relief valve in the plenum chamber so as to reduce the opening and closing of the pressure relief valve due to pulsations caused by the engine operation. In one embodiment, the pressure is relieved by discharging the air to the exhaust system for silencing and also for cooling the exhaust gases. In other embodiments, the air for pressure relief is discharged to the atmosphere.

Abstract: A decompressor for an internal combustion engine including a mounting hole in which a decompression valve for opening and closing a pressure relief bore opening into a combustion chamber within a cylinder of the engine, is disposed, and also including a through-hole which is obliquely and rectilinearly formed through a portion of a wall of the cylinder, and through which an outer open end portion of the mounting hole is able to communicate with a scavenging passage of the engine.

Abstract: A two stroke internal combustion engine includes a cylinder with a piston slidably sealed in the cylinder, a plurality of transfer ports open into the cylinder and at least one exhaust port leads from the cylinder, the transfer ports are connected to a common inlet manifold and a common valve member is provided to regulate the flow of air from the inlet manifold to the transfer ports and to vary the flow of air through one transfer port relative to the flow of air through at least one other transfer port.

Abstract: An internal combustion engine comprising an engine block defining a cylinder bore and including an exhaust passage communicating with the cylinder bore, a cylinder liner which is housed in the cylinder bore and which includes an exhaust port communicating with the engine block exhaust passage, and structure on one of the engine block and the cylinder liner for permitting one of the engine block and the cylinder liner to expand adjacent the exhaust port.

Abstract: A two-cycle, crankcase compression, internal combuston engine and a piston liner therefore having an exahust port opening that is chamfered along its top edges so as to reduce the likelihood of piston ring sticking without affecting the port timing. Different forms of chamfering tools are depicted.

Abstract: A cylinder block includes a cylinder with a piston therein and a main crankcase. A combustion space is disposed above the piston and a compression space is disposed below the piston. An exterior passage including a reservoir transfers compressed air from the compression space to the combustion space. A first valve permits one-way flow of ambient air into the compression space, and a second valve permits one-way flow from the compression space into the passage so that the compression process is independent of the combustion process. In one embodiment, the exterior passage includes a first passage for air and a second passage for fuel-air mixture for selective communication with the combustion chamber. In another embodiment, an inner crankcase is disposed within and spaced from the main crankcase and incorporates the first and second valves.

Abstract: For the purpose of preventing a decompression passageway in a two-cycle engine from being blocked by carbon soot, facilitating manufacture of a two-cycle engine having decompression structure and eliminating reduction of output power of the two-cycle engine caused by the decompression structure, a known two-cycle engine includes a scavenging passageway formed along an inner wall of a cylinder. The scavenging passageway is directed in the axial direction of the cylinder and communicates with a crank case of the engine. A decompression groove extends in the axial direction of the cylinder on the upstream side of a cylinder cooling airflow at a top end portion of the scavenging passageway. The width and depth of the decompression groove are either varied along the axial direction of the groove so as to be narrowed towards a tip end thereof directed toward a plug, or are provided with a narrowed portion of venturi shape.

Abstract: A lengthwise scavenging system for a two stroke internal combustion engine comprising a ported cylinder, a piston, a wave formed sleeve which is attached to the piston, and a reentrant cylinder head which provide annular recess for the sleeve. The inlet ports and the exhaust ports are displaced longitudinally and latitudinally at different levels relative to the cylinder. The uppor ports are controlled by the top portion of the sleeve, and the lower by the bottom to perform lengthwise scavenging.

Abstract: A two stroke engine has a closed plane cylinder with an inlet port and outlet port disposed on opposite sides of the cylinder towards the open end thereof. A piston is slidingly sealed in the cylinder the piston having a head portion which is slidingly sealed with the wall of the cylinder and a connecting rod portion which extends axially from the head portion. The end of the connecting rod portion remote from the head portion is connected to a crank on a crankshaft, the ports being disposed one on each side of the vertical axial plane of the crankshaft so that; upon downward movement the piston will tilt, opening the exhaust port before the inlet port and; upon upward movement the piston will tilt closing the exhaust port before the inlet port, the throw of the crank producing a maximum piston tilt of up to 10.degree.. A multi-cylinder engine may comprise a plurality of piston/cylinder assemblies described above, disposed radially of one another about a common crankshaft.

Abstract: The invention relates to a pulsation controller in the intake/exhaust systems of internal combustion engines inclusive of two-cycle gasoline engines, four-cycle engines and rotary piston engines, and includes a device for detecting by means of a sensor pulsation in the intake/exhaust pipes connected to a cylinder, and a control means for allowing the desired pressure wave in the pulsation to coincide with the given position of the intake/exhaust system by the detection result obtained by this sensor. The phase of a standing wave in the intake/exhaust system of the engine is detected to control the impedance or the timing for opening and closing valves or ports in the intake/exhaust system and, hence, the phase of a standing wave in the intake/exhaust system, thereby improving the intake/exhaust efficiency for more efficient operation.

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: A control valve driving device wherein a control valve is provided in an intake or an exhaust system of an internal combustion engine and means for driving this control valve in response to an operating condition of said internal combustion engine is provided. An opening angle of the control valve is operable to be changed to permit an intake or an exhaust characteristic to be changed. The control valve driving device is characterized in that the control valve can be driven only when a pressure in an intake or an exhaust pipe is at an acceptably low level.

Abstract: An internal combustion engine includes a single sluice (3) which opens asymmetrically and one-sidedly in an exhaust channel (5) and which runs tangentially within the cylinder (1), diagonally to the cylinder head. A rotating flow is thus obtained in the cylinder along its inner wall, thus ensuring a complete and reliable ignition, a low fuel consumption and a low pollutant content in the exhaust gases.

Abstract: Two stroke gasoline spark ignition supercharged engine wherein air scavenging takes place without loss of fuel and full charge of air and fuel at optimum combustion ratio takes place for each power stoke with flywheel smoothed interrupted fuel injection for reduced power requirements. A modified valve design having a deflector lip is disclosed which further improves scavenging over the standard valve configuration.

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: In the case of a high-speed, port-controlled two-stroke internal combustion engine with crankcase scavenging with at least one cylinder having in each case at least one suction duct with an inlet port, with in each case at least one outlet duct with an outlet port and with at least one scavenging duct with a transfer port, the inlet, outlet and transfer ports being arranged on the cylinder inside, the geometrical construction of the suction duct (4) and/or outlet duct (6) is such that the engine noise is reduced throughout the speed range, while increasing the engine efficiency and while simultaneously improving the specific fuel consumption.

Abstract: A cylinder liner comprising a generally cylindrical outer wall, a generally cylindrical inner wall defining a cylinder having a bottom end, and an exhaust port communicating with the cylinder and being defined by an upper wall extending between the inner and outer walls and being curved concavely with respect to the bottom end, a lower wall extending between the inner and outer walls and being curved convexly with respect to the bottom end, and opposite side walls extending between the inner and outer walls and between the upper and lower walls and converging toward the bottom end of the cylinder.

Abstract: A porting system for two-cycle internal combustion engines has two exhaust ports located on diametrically opposed sides of the cylinder. A pair of intake or by-pass ports are symmetrically positioned on each side of the two exhaust ports. The flow of fuel mixture is laminar and has a pattern which is inward and slightly upward from each intake port. As incoming streams collide, the gas flows upwardly and forms two mushrooms. Then, the flow is downwardly along the cylinder axis. The downward flow divides into two streams flowing radially outwardly from the center of the cylinder and out the two exhaust ports. With this flow pattern, there is a minimum of mixing of intake and exhaust gases, and as compared to the prior art, more unburned gas is retained in the cylinder to improve power output and reduce fuel consumption.

Abstract: A suction device suitable for use with a two-cylinder internal combustion engine including a second suction port formed at a wall of at least one of the pair of cylinders in a position in which it is opened and closed by a piston in the cylinder, and a second conduit allowing the second suction port to communicate with a carburetor therethrough.

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: 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: The invention relates to a method and to a port-controlled two-stroke internal combustion engine in which the cross-sections of the intake and outlet are so constructed in the direction of the longitudinal axis of the cylinder that in the case of an upward or downward movement of the piston, the noise-generating intake and outlet pressure gradients and amplitudes are reduced by the gradual opening of the particular intake and outlet, the piston lower edge and intakes having special constructions.

Abstract: The invention relates to an intake duct for feeding mixture or air to a four-stroke internal combustion engine cylinder provided with the usual intake valve or valves, non-return valve means being provided in said duct in series with said intake valve or valves, said non-return valve means being arranged to allow the flow of mixture or air to said cylinder, and being arranged to prevent the reverse flow of mixture returned by the cylinder, from the intake duct to the outside.