Abstract: A two-cycle internal combustion engine includes a control valve disposed in a communicating passage for communicating the combustion chamber to a chamber portion adjacent to the combustion chamber. The control valve controls the opening and closing of the communicating passage. A fuel or an air-fuel mixture is supplied into the combustion chamber through the communicating passage. The fuel injection opening of the communicating passage has a height which is smaller than the distance between outermost side surfaces of the piston rings to reduce the amount of the air-fuel mixture or combustion gas leaking from the combustion chamber into the crank chamber through gaps between the piston and the opening. Therefore, reduction in engine output or seizure of the piston due to local temperature rise is avoided.

Abstract: The present invention pertains to the field of engine construction and relates to internal combustion engines with scavenging and more precisely to two-stroke engines. At the beginning of the exhaust stroke, the exhaust gases are expelled from the engine cylinder through inlet and outlet ports, inlet and outlet passages and slide valves into an exhaust pipe. Scavenging ports are then uncovered by an upper edge of the piston and used to feed a fresh charge into the cylinder from the crank chamber while the cylinder cavity is scavenged. After expelling the exhaust gases from the cylinder cavity, the slide valves rotate to interrupt the communication between the cylinder cavity and exhaust manifold. Upon further rotation of the slide valves, the cylinder cavity is connected with the inlet pipe through the same gas-distribution organs used for the exhaust gas outlet, i.e. the inlet and outlet ports, the inlet and outlet passages and the slide valves.

Abstract: An exhaust passage for connecting to an exhaust port of a cylinder is provided. The exhaust passage includes a first path extending in a direction generally orthogonal to the central axis of the exhaust port. A second path connects the first path and the exhaust poil and a control valve is provided in the first path. The rotational axis of the exhaust control valve is generally parallel to the direction in which the first path extends. The surface area of an opening connecting the first path and the second path is variable as the exhaust control valve rotates, so as to carry out controlled combustion and exhaust timing. This makes it unnecessary to provide a hollow section for housing an exhaust control valve and bearing at a position close to the exhaust. It is also possible to reduce the size of a cylinder block and to realize smooth flow of exhaust gases by making the inner peripheral surface of the exhaust passage smooth.

Abstract: The present invention is a stratified scavenging two-cycle engine which has a more compact structure. The stratified scavenging two-cycle engine includes a scavenging flow passage (3) for connection between a cylinder chamber (4a) and a crank chamber (1a); and an air flow passage (2) connected to the scavenging flow passage (3), the scavenging flow passage (3) is continuously formed by a communication portion (30) extending from the crank chamber (1a) toward the cylinder chamber (4a) side; and a scavenging direction adjustment portion (31) extends from the communication portion (30) toward a cylinder inner surface (4b) side and opens at a scavenging port (3a) in the cylinder inner surface (4b). The air flow passage (2) extends into an area surrounded by the communication portion (30), the scavenging direction adjustment portion (31), and the cylinder inner surface (4b).

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: A control arrangement for a planing-type boat having an engine powering a water propulsion device is disclosed. The engine has at least one combustion chamber, an exhaust port leading from the combustion chamber, and an exhaust timing valve cooperable with the exhaust port. The exhaust timing valve is moveable between a first retracted position and a second extended position, where in the second position a flow of exhaust through the exhaust port has a shorter duration than when the valve is in the first position. A drive unit is associated with the exhaust timing valve. The control is arranged to move the exhaust timing valve with the drive unit from the second position towards the first position at a predetermined high engine speed. The control is arranged to prevent the rapid movement of said exhaust timing valve between its first and second positions when the engine speed fluctuates about the predetermined engine speed.

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: 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 includes a control valve disposed within a communicating passage between the combustion chamber and a chamber portion adjacent to the combustion chamber. The control valve is for controlling the opening and closing of the communicating passage. Blowby of an air-fuel mixture supplied to the combustion chamber can be prevented to reduce fuel consumption and increase the exhaust gas purifying performance. A communicating passage portion between the control valve and the fuel supply opening is configured to spray fuel from the control valve to a part or all of a wall surface of the communicating passage portion and the wall surface of the communicating passage portion is shaped to guide the fuel into the combustion chamber.

Abstract: The present invention is referred to an exhausting valve lid for motorcycles comprising a lid body including several orifices for fastening said lid to the motorcycle engine. Said lid includes means for controlling the force to be applied to the exhausting valve regulating means, controlling therefore the time at which the exhausting valve is to be opened. Said means for controlling the force to be applied comprises a hollow housing projected from the outer surface of lid body, said housing receives a cylindrical hollow aluminum bolt engaged to a pressing spring coupled to said exhausting valve regulating means.

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 supercharged internal combustion engine having a intake valve positioned in and part of the cylinder block wall and a exhaust valve in the cylinder head providing a regulated flow of gasses from bottom to top combustion chamber when scavenging and also isolating the piston rings lubricated with oil to minimize the contamination of the combustion chamber, exhaust gas and crankcase oil.

Abstract: An improved two cycle internal combustion engine, preferably of a stepped piston type, having a unique arcuately shaped transfer deflector valve, which varies by its controlled sliding movement within an inlet passage, the size of exposed opening of an elongated inlet port in the cylinder. The inlet port extends circumferentially part way around the cylinder. The leading end of the valve is preferably angled, in cooperation with the preferably almost tangent orientation of the inlet passage, to induce arcuate movement into each fresh full charge entering the combustion chamber for enhanced fuel charge mixing. In the preferred embodiment, two such valves are symmetrically positioned around the cylinder and arcuately move in unison between closed and open positions over corresponding opposing inlet ports.

Abstract: A combustion controller for a two-cycle engine which enables to cause self firing always at the optimum timing is provided. The combustion controller comprises an exhaust control valve 15 provided in the vicinity of an exhaust port 7 of the two-cycle engine 1 and capable of fully closing the exhaust port and driving control means 47, 38, 39, 40 and 37 to drive the exhaust control valve 15 according to a control map giving an exhaust opening ratio .theta..sub.e depending at least on the engine speed and the throttle valve opening ratio .theta..sub.th in order to control the pressure in the cylinder during up-stroke of the piston 8.

Abstract: An exhaust control valve arrangement for a two cycle internal combustion engine for altering the compression ratio to provide optimum running under all conditions. An arrangement is provided or cleaning the exhaust control valve and its surrounding cooperating surfaces of the engine upon shutting off of the engine to preclude the formations of deposits that can cause sticking of the valve element. The valve element is rotated through a number of cycles after the engine is stopped through a wider range than during its normal valving operation for removing deposits. The number of cycles is chosen in response to an engine condition such as length of time of running or amount of lubricant supplied to the engine. Various valve arrangements are disclosed that improve the cleaning operation and permit cleaning even while the engine is running.

Abstract: Air/fuel mixture supply device for a two-stroke internal-combustion engine, of the type with scavenging by compressed air in the casing, comprising at least one cylinder, a piston capable of reciprocating motion in the cylinder, and a scavenging-air compression casing, the cylinder comprising at least one exhaust port, at least one transfer port and a port for introduction of an air/fuel mixture.A rotary closure member (19) driven in synchronism with the rotation of the engine is associated with the port (16) for introduction of the air/fuel mixture into the combustion chamber, this closure member being placed in an air reservoir (14) fed with air under a pressure greater than the pressure in the combustion chamber (10) after opening of the exhaust port (11).

Abstract: A two-cycle crankcase compression diesel engine having a scavenge control system for controlling the amount of scavenging flow and an exhaust control system for controlling the effective compression ratio and the effective flow area of the exhaust system. These controls are operated during normal engine running conditions at most speed ranges from a three dimensional map. However, special control routines and valve operating arrangements are provided for pre-starting, starting, idle, engine braking or deceleration and rapid acceleration so as to improve the running under these transient or non-normal conditions.

Abstract: A polymer composite reed for a reed valve is provided, wherein the reed has improved mechanical properties as a result of its construction and is highly resistant to chemical and thermal attack. The improved mechanical properties of the reed are primarily due to the reed being reinforced with two plies of fabric having a harness satin weave, which provides the reed with a flexural modulus that is substantially greater in one direction of the reed. The chemical and thermal properties are primarily due to the semicrystalline thermoplastic material from which the reed is formed. In addition, the thermoplastic material enhances the fracture toughness of the reed to improve the durability of the reed. As a result, the reed is highly suitable for applications requiring long life under high speed, cyclic loading, such as that found in two-stroke and four-stroke internal combustion engines for the automobile industry.

Abstract: An exhaust control valve arrangement for a two cycle internal combustion engine for altering the compression ratio to provide optimum running under all conditions. An arrangement is provided for cleaning the exhaust control valve and its surrounding cooperating surfaces of the engine upon shutting off of the engine to preclude the formations of deposits that can cause sticking of the valve element. The valve element is rotated through a number of cycles after the engine is stopped through a wider range than during its normal valving operation for removing deposits. The number of cycles is chosen in response to an engine condition such as length of time of running or amount of lubricant supplied to the engine. Various valve arrangements are disclosed that improve the cleaning operation and permit cleaning even while the engine is running.

Abstract: A number of embodiments of improved reed valve mechanisms for reciprocating machines wherein an arrangement is provided by employing a magnet releasably restraining the valve element in one of its positions so as to permit a stiffer valve to be employed while, at the same time, insuring against loss of volumetric efficiency and control. An adjustable stopper plate is also described.

Abstract: A two stroke cycle engine cylinder block (9) has exhaust ports (14) controlled by power valves which rotate on an axis extending longitudinally of the block (9). Along this axis the block (9) has a plurality of aligned recesses in which are located bearing members (24) for the power valves. Bores (25) in each bearing member (24) are axially aligned and the bearing members (24) immobilely retained in the aligned recesses by assembly of the exhaust manifold (16). Spigots on the power valves are received in the bores (25) and coupled together so that the power valves rotate in unison.

Abstract: An improved reed valve arrangement for a two cycle engine wherein in addition to the normal reed valve elements and stopper plates, there are provided rectifier plates that define a flow passage so as to direct the charge away from the walls of the engine that define the associated intake passage.

Abstract: An exhaust timing controller for a two-stroke cycle engine includes an exhaust timing control valve for changing a height of an open edge portion on a top dead center side of an exhaust port opening to an inside wall surface of a cylinder bore in the engine. The exhaust timing control valve moves axially of the cylinder bore by power from an actuator and the exhaust timing is accelerated in response to rotational frequency rises in the engine. The power of the actuator is transformed into an elevating stroke of the exhaust timing control valve by the eccentric motion of an eccentric cam. A slider mechanism for transferring an eccentric motion of the eccentric cam to the exhaust timing control valve is provided between the eccentric cam and the exhaust timing valve. A straightening member extends smoothly from a portion of the exhaust timing control valve, which retracts into the exhaust port, on the downstream side of the exhaust port.

Abstract: The present invention includes an internal combustion engine having at least one piston reciprocating within a cylinder, and an exhaust port allowing communication of the cylinder with an exhaust passage. A moveable shutter is provided to vary the effective area of the exhaust port. The shutter varies the effective area cyclically in a timed relationship to the reciprocal motion of the piston within the cylinder. A sensor is provided to measure an operating characteristic of the engine and to generate signals responding to the operating characteristic sensed. A control unit is provided to process the signals and to control the motion of the shutter in response to the signals.

Abstract: A cylinder head for an internal combustion engine of either a two-cycle operation or a four-cycle operation is disclosed. The cylinder head includes an intake port, an exhaust port, a dual-function chamber, a poppet valve positioned within the dual-function chamber, and a flapper valve also positioned within the dual-function chamber, capable of sealing the intake port from the dual-function chamber, capable of sealing the exhaust port from the dual-function chamber. If the cylinder head is for a two-cycle engine, an injector may be positioned within the cylinder head so that fuel is injected either within the dual-function chamber, or directly injected within the combustion chamber. A process of operating the cylinder head in conjunction with an internal combustion engine is also disclosed.

Abstract: Rotating valves are set forth especially for use in two stroke internal combustion engines. The valve has two rotating parts which come into tangential pseudocontact with each other. Each rotating part has a solid surface of revolution which closes off flow and a recessed portion which permits flow.

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: A superchargeable multi-cylinder 2-stroke cycle internal combustion engine employs opposite reciprocating mult-port slide valves in guideways on opposite sides of the engine block, to open and close cylinder air supply and combustion gas discharge conduits in several variations. Use of opposite multi-port slide valves driven from the engine crankshaft simplifies engine design, and improves scavenging of combustion gases from piston chambers of either spark-ignition or diesel engines. A preferred variation channels air supply and combustion gas discharge flows through dual passageways of opposite air preheating manifolds, to increase engine fuel efficiency, Further development of the preferred variation can result in production of simplified, compact, supercharged 2-stroke spark-ignition and diesel engines of improved design.

Abstract: An improved apparatus and method of construction of a reed valve mechanism having a cushioned reed valve seat is disclosed. The present invention provides a smooth resilient overlay plate which is attached around ports in a reed cage. The benefits of conventional rubber coated reed cages is supplied without the expenses inherent in previous construction methods. Various mechanical mounting means are disclosed for ease in construction and improved reed valve performance.

Abstract: The present invention provides improved multiple stage reed valve construction for internal combustion engines. The reed valves comprise first stage reed valves with multiple ports in the first stage reed valve. Beams having a smoothly shaped curve from the base of the first stage reed valve to the apex thereof and narrowing toward the apex separate adjacent ports. The reed valves of the present invention provide significant improvements in engine operation.

Abstract: A variable compression ratio mechanism for a two cycle diesel engine embodying auxiliary exhaust passages and auxiliary exhaust ports that communicate with the cylinder above the main exhaust ports and in which control valves are positioned for controlling the opening and closing of the auxiliary exhaust ports to change the effective compression ratio of the engine to minimize dead space between exhaust control valves and the auxiliary exhaust ports, the exhaust control valves are positioned in close proximity to the cylinder and comprise valve elements that operate in bores that are disposed substantially parallel to the cylinder bore. Both rotary and reciprocating type valves are disclosed and various mechanisms are disclosed for interlinking the control valves for simultaneous operation.

Abstract: A diesel engine operating on the two cycle crankcase compression principle and having a means for reducing nitrous oxide emissions under low and medium range speeds. This is done by throttling the scavenge air flow which can be accomplished either by throttling the air admitted to the crankcase chamber or bypassing a portion of the compressed air from the crankcase chamber back to the induction system. In addition, an exhaust control valve is provided for raising the compression ratio and the injection timing is advanced when the scavenge air is reduced so as to further improve the control of hydrocarbon and carbon monoxide emissions.

Abstract: The present invention provides improved multiple stage reed valve construction for internal combustion engines. The reed valves comprise first stage reed valves with enlarged ports, enlarged second stage reed valves corresponding with the ports, and one or more webs positioned in the ports to help support the second stage reed member when it is in a closed position. The reed valves of the present invention provide significant improvements in engine operation and tremendous increase in reed valve operational life.

Abstract: The invention provides improved reed constructions for use in a reed valve assembly suitable for use in the induction porting of two-stroke internal combustion engines. The reeds incorporate improved hinge designs and dual-stage reed arrangements in which both primary and secondary reeds incorporate ports which do not overlap one another to improve flow through the dual-stage reed assembly involved.

Abstract: In an engine wherein there is only one exhaust valve per cylinder, the single exhaust valve is maintained closed while an inlet valve, via which an air-fuel mixture is exclusively admitted to the combustion chamber, is open. A second inlet valve, via which only air is supplied into the combustion chamber, is arranged to open when the exhaust valve is opened. In this manner, fuel is prevented from passing through the combustion chamber to the exhaust system. While the second inlet valve is open, air which contains no fuel is used to scavenge the combustion gases. In engines wherein there are two exhaust valves per cylinder, it is possible for a stoichiometric air-fuel mixture to be formed in the combustion chamber. In this configuration one of the two exhaust valves is opened during an initial stage of the exhaust phase, and the combustion gases are exhausted into a three-way catalytic converter.

Abstract: An auxiliary exhausting device for improving the scavenging efficiency and the combustion efficiency of a two-stroke engine is provided. The auxiliary exhausting device includes an inner rotating member and an outer rotating member both having an opening communicable with an auxiliary exhausting port, two timing wheels respectively fixed to the inner and outer members with the one, which is fixed to the inner member, driven by the crankshaft, a positive driving device rotating the outer member, and a controller responsive to the operating condition of the engine for so controlling the positive driving device that the outer member is always desiredly rotated.

Abstract: An electromagnetic auxiliary exhausting device enabling a two-stroke engine to have an improved scavenging efficiency and an improved combustion efficiency is provided. The device includes an electromagnetic valve mounted on the engine cylinder, an actuator, and a controller responsive to an operating condition of the engine for controlling the actuator. The valve includes a movable valve needle component having a first seat surface, an immovable valve body having a second corresponding seat surface, a spring for tightly matching the seat surfaces against each other, and a coil energizable by a current pulse outputted from the actuator to result in an electromagnetic force capable of overcoming the force effected by the spring.

Abstract: A rotary commutator valve that is located at the exhaust ports of the cylinder of an internal combustion, reciprocal engine for regulating the flow of exhaust and allowing the exhaust ports to be sequentially utilized as supplementary intake ports for charging the engine cylinder, the communtator valve having an exhaust passage, an intake passage and a common exhasut/intake passage that communicates with the exhaust ports and a rotor with a rotor notch that sequentially and selectively connects either the intake passage or the exhaust passage to the common exhasut/intake passage allowing the exhaust ports to first exhaust combustion gases and then form supplemental intake ports for admitting additional air.

Abstract: The present invention provides an improved single stage or multiple stage reed valve for use in an air intake of an internal combustion engine. The multiple stage reed valve of the preferred embodiment includes a relatively stiff first stage reed member having ports therein, a relatively flexible second stage reed member comprising multiple reed petals to control flow through the ports in the first stage reed, and means to join each reed petals to an adjacent reed petal to cause the reed petals to move substantially in unison with one another. The present invention provides a reed valve with increased life and which is resistant to material fatigue even under conditions of uneven flow through the air intake.

Abstract: A rotary exhaust valve is provided in an exhaust passage of an engine, which is rotated by the engine. A valve phase control device is provided for changing the phase of the rotary exhaust valve. An actuator is provided for actuating the valve phase control device so as to change the phase of the rotary exhaust valve in accordance with engine operating conditions.

Abstract: A two-cycle engine having a fuel injector, scavenge port and an exhaust port is provided with a scavenge pump for supplying scavenging air into a cylinder. An exhaust rotary valve is connected to the exhaust port to open and close the port. Similarly, a scavenge rotary valve is connected to the scavenge port to open and close the port. Engine operating condition including engine speed and degree of depressing the accelerator pedal, representing the engine load, is inputted to a control unit, which variably controls the timings of opening and closing the exhaust and scavenge rotary valves in accordance with the engine operating condition.

Abstract: In a two cycle internal combustion engine (2), a turbulence generator (70) is provided by a freely rotating fan (72) in the fuel-air stream to the reed valves (16) which supply the fuel-air mixture into the crankcase chamber (8). The freely rotating fan (72) is driven by the fuel-air mixture flow and rotates to generate turbulence to provide more uniform distribution of the fuel-air mixture.

Abstract: Four power cylinders within an engine and/or cylinder block are distributed around a central bore containing a rotary valve whose axis of rotation is parallel to that of each of the cylinders. Supercharger cylinders are axially aligned with the power cylinders and pistons within the power cylinders are connected by a rod to pistons within the supercharger cylinders and driven by a common power means. The power means drives alternate cylinders around the valve in phase and intermediate cylinders 180.degree. out of phase. Air intake means through the rotary valve is fed into ports of opposite supercharger cylinders through a Y-shaped passage. Compressed air or a fuel mixture from the supercharger cylinders is fed through a passageway to the power cylinders in intake phase. If a four stroke cycle engine is involved, the passage may be Y-shaped connecting two supercharger cylinders to a single power cylinder.

Abstract: A kit for post-installing reed valves between the cylinder block of a 2-cycle engine of a jet propelled small-sized boat and an inlet manifold is characterized in that the kit comprises base plate, a carburetor plate and a reed valve case interposed between two plates. The base plate is formed with two types of holes, i.e., plain holes through which attaching bolts are screwed into threaded holes in a cylinder block and threaded holes to be used in attaching the reed valve case. The carburetor plate and reed valve case are formed with plain holes, respectively, for alignment communication with the threaded holes in the base plate to receive other bolts. The arrangement is such that the reed valves removably fitted in the reed valve case are inseparably held between the reed valve case and the carburetor plate. Thus, the 2-cycle engine can be efficiently changed from the piston valve type to the reed valve type.

Abstract: A system incorporating a pivotally mounted control valve to selectively close the upper portion of an exhaust port in a two-cycle engine including a motor coupled with the valve for driving same. A speed determination means is provided to determine the engine speed relative to a specified value. A drive means rotates the motor in either direction based on the sensing by the speed determination means. A drive current control means detects the magnitude of change of the engine speed and increases or decreases the current supplied to the motor to increase or decrease the speed of change of the control valve.

Abstract: A two-cycle engine includes a port timing control device including a port timing control valve which is mounted on a cylinder block and has a timing control surface. The control valve is movable in a plane substantially perpendicular to the axis of a cylinder between a closed position where the valve is disposed in an exhaust passage with the control surface closing the end portion of the exhaust port closer to a cylinder head and an open position where the valve is held out of the exhaust passage to open the end portion of the exhaust port. The control surface is of an arcuate concave shape and having a curvature substantially equal to that of an inner peripheral surface of the cylinder so as to be smoothly continuous with the inner peripheral surface of the cylinder.

Abstract: Reed valves for internal combustion engines are disclosed, the reed valves having protective coating of synthetic rubber.

Abstract: A substantially annular flow enhancing insert is positioned in the carburetor side of the roof prism shaped reed valve inlet frame of a two-cycle internal combustion engine. The insert's flow passage is shaped so as to prevent flow separation due to large angular changes in the flow passage. The insert has two extended tapering wedges, each wedge positioned flush against the inner surface of the two opposite parallel triangular walls of the inlet frame. Each wedge directs the inlet flow smoothly to the reed valve openings and eliminates flow passage discontinuities that are normally present within the inlet frame. The remainder of the insert is closely matched to the carburetor duct and reed valve inlet frame contours so as to eliminate surface discontinuities and thereby enhance the flow into the engine.

Abstract: A two-cycle engine includes a port timing control device for varying a timing of the opening of an exhaust port by a piston. The port timing control means includes a first valve mounted within an exhaust passage adjacent to an upper end of the exhaust port and having a port timing control surface, a second valve mounted on a cylinder block between a cylinder head and the first valve and having a closure surface, and an urging member acting on the second valve to always urge it against the first valve. The first valve is operable to be angularly moved about an axis generally perpendicular to the axis of a cylinder into and out of an extended position where the control surface is disposed slightly below the upper end of the exhaust port to close a part of the exhaust port. The second valve is movable along a generally straight path into and out of an extended position where the closure surface closes that portion of the exhaust port lying between the upper end of the exhaust port and the first valve.

Abstract: A two-cycle engine includes a pair of first and second valves movable into and out of respective closed positions where the first and second valves close part of an exhaust port to vary an exhaust timing thereof. Power transmission means includes a pair of first and second shafts angularly movable about their respective axes disposed parallel to an axis of a cylinder and each having a pinion portion. A rack rod is movable along an axis thereof perpendicular to the axis of the cylinder, the rack rod having first and second rack portions meshingly engaging the pinion portions of the first and second shafts, respectively, in such a manner that the angular movement of the first shaft causes the angular movement of the second shaft through the rack rod. A pair of first and second levers of a generally L-shape defined by a pair of perpendicularly-disposed first and second arms has a corner portion where the first and second arms merge.