Abstract: The disclosure concerns a method and a control arrangement for controlling valve actuation of an ICE comprising an exhaust valve, an intake valve, and a turbo compressor. The method comprises and the control arrangement is configured to: limiting/limit valve actuation changes of the exhaust and intake valves based on compressor data including surge limit data for the turbo compressor and one or both of a current turbo compressor rotational speed and a current turbo compressor pressure ratio, to maintain a turbo compressor mass flow above a limit mass flow value.

Abstract: A breather device and a snow removal machine having the breather device have a casing into which blowby gas of an engine flows, an air suction port for letting out gas from the inside of the casing, and a gas-liquid separation mechanism for separating moisture contained in the blowby gas. The gas-liquid separation mechanism separates an inlet, which allows the blowby gas to flow in, and the air suction port by a predetermined distance, and has the air suction port positioned above a liquid path through which the moisture flows. A gas path allows the blowby gas to flow from the inlet to the air suction port without passing through an air cleaner element.

Abstract: This invention relates to the field of opposed-piston engines having two pistons in one cylinder configured to have facing heads. Specifically, this is an engine with two crankshafts, two piston heads facing each other in a single cylinder, with the following features: compact size relative to a comparable design, improved or equivalent performance to a comparable design as a result of any of the following: locating crankshafts in a different plane from the cylinder axes; the use of shared duct structures; and the use of an embedded compressor chamber for efficient operation to cover all volumetric requirements, fulfilling the entire thermodynamic cycle, and performing in addition the sweeping and overloading of air or an air/fuel mixture in the cylinder combustion chamber in each revolution of two or more crankshafts, either with or without advancement between the crankshafts.

Abstract: A valve for a marine propulsion unit comprises a valve body (11) having an end face (13) and a wall (14) extending from the end face. An aperture (15) is defined in the end face. A valve stem (12) is moveable within and with respect to the valve body, such that, in the closed state of the valve, the valve stem closes the aperture. A maximum width (d1) of the valve stem is greater than the width (d2) of the aperture in the end face of the valve—so that, if the valve stem should fracture, the detached portion(s) of the valve stem will be retained in the valve body. The valve may for example be used as a cylinder drain valve in a marine propulsion unit.

Abstract: Methods and systems are provided for providing exhaust gas recirculation to a naturally aspirated internal combustion engine. In one example, exhaust gas is recirculated to an engine intake via a dedicated scavenging manifold and a scavenging exhaust valve. The exhaust gas and fresh air that has not participated in combustion may be recirculated to engine cylinders even at high engine loads since the exhaust gas and fresh air is returned to the engine air intake at a pressure greater than atmospheric pressure.

Abstract: A control device for a vehicle including a variable compression ratio mechanism arranged to vary an engine compression ratio of an internal combustion engine, and a torque converter which includes a lock-up mechanism, and which is disposed between the internal combustion engine and a transmission, has a controller configured to switch the engine compression ratio from a high compression ratio to a low compression ratio, and to switch the lock-up mechanism from a lock-up OFF state to a lock-up ON state. When the controller is switching the engine compression ratio from the high compression ratio to the low compression ratio, the controller starts switching the lock-up mechanism to the lock-up ON state when a current engine compression ratio is equal to or smaller than a permissible compression ratio which is between the high compression ratio and the low compression ratio.

Abstract: The invention provides an internal combustion engine comprising a piston mounted for reciprocating linear motion within a cylinder along a cylinder axis. The piston is coupled to an output shaft by a power transfer assembly arranged to convert linear motion of the piston to rotary motion of the output shaft. The piston has a first head moveable within a first chamber and a second head opposite the first head and moveable within a second chamber. The power transfer assembly has a lubrication system for lubricating moving components of the power transfer assembly. The lubrication system is sealed from the first chamber and the second chamber to prevent the passage of fluid from the lubrication system into the first chamber and the second chamber.

Abstract: A linear-acting, free-piston internal combustion engine suitable for operation on a four-stroke engine cycle comprises a power piston (11a, 11b) reciprocating in a power chamber (18a, 18b) and a compression piston (23, 23a, 23b) reciprocating in a compression chamber (29a, 29b). The power piston (11a, 11b) and the compression piston (23, 23a, 23b) are rigidly connected by means of a rod (19). The compression piston (23, 23a, 23b) performs alternately an intake stroke and a compression stroke and the power piston (11a, 11b) performs alternately a power stroke and an exhaust stroke.

Abstract: The invention relates to a volume-controlled four-stroke reciprocating internal combustion engine comprising a first cylinder, in which a first piston that is operationally connected to a crankshaft via a first connecting rod, is arranged so as to be displaceable in a reciprocating motion, and at least one second cylinder, in which a second piston that is operationally connected to the crankshaft via a second connecting rod is arranged so as to be displaceable in a reciprocating motion. The engine further includes a fresh air tract for the second cylinder, in which an expansion/compression machine is arranged in the direction of flow of fresh air before a gas exchange inlet valve of the second cylinder, wherein the expansion/compression machine is the first cylinder. The volume-controlled internal combustion engine as per the invention has great potential for saving fuel and thereby for reducing CO2.

Abstract: One non-limiting object of the present invention is to provide modifications to conventional in line 6 cylinder engines capable of increasing their efficiency in operation. This includes modifying the central two adjacent piston and cylinder assemblies of the engines. The modifications involve (1) changing the camshaft so that the central two adjacent piston and cylinder assemblies have their four stroke cycles in phase rather than 180° out of phase, (2) providing a communicating passage between the combustion chambers of the central two piston and cylinder assemblies and (3) modifying either the hardware or programming for the control of the fuel injectors of the central two piston and cylinder assemblies so that they can be selectively controlled not to inject fuel during the operation cycle thereof.

Abstract: The disclosure relates to reciprocating piston engines having four cylinders with a circular cross section, cylinder axes which are parallel to one another, and an output shaft. The cylinder axes, as viewed in axial section, lie at the corner points of a rectangle that is a square, with the output shaft, which extends parallel to the cylinder axes, in the center of the square. Each pair of cylinders which lie diagonally opposite one another are arranged in the same direction, as viewed axially, and in opposite directions, as viewed axially, with respect to the other pair of cylinders. The force or moment from each cylinder is transmitted to the output shaft via a dedicated rotating crank and a toothing system.

Abstract: A multi-cylinder engine with a crankcase integrated cylinder block including a cylinder block having a plurality of cylinder bores, a plurality of crank chambers formed by an upper crankcase and a lower crankcase, a bulkhead that partitions between the cylinder bores and the crank chambers, and a honing release portion having a cylindrical honing release surface formed continuously with the cylinder bore in the upper crankcase and the bulkhead. The honing release surface forms an arcuate recessed portion in the bulkhead, the bulkhead is formed with a communication hole that includes a first opening edge on a side of the cylinder bore, a second opening edge on a side of the crank chamber having an opening width decreasing with a distance from the cylinder bore, and a third opening edge that extends substantially in parallel with the cylinder axis.

Abstract: According to a drive controlling method, the engine is driven in the forward direction by a predetermined reference torque, and the position of the rotation angle of the engine driven in the forward direction is judged based on information concerning whether the rotation angle has passed through the first top dead center in the forward movement of the engine, the amount of forward movement of the engine driven in the forward direction and the amount of reverse movement of the engine driven in the reverse direction.

Abstract: A vehicle control apparatus (100) for controlling a vehicle (10) provided, as a drive system, with: an internal combustion engine (200) in which a compression ratio is variable; and a transmission (500) which has a torque converter (300) and a lockup mechanism (400) between an input shaft and an engine output shaft (205) of the internal combustion engine and which can change a ratio between a rotational speed of the input shaft and a rotational speed (Nout) of an output shaft coupled with an axle, is provided with: a first controlling device for changing an operating state of the lockup mechanism in accordance with an operating condition of the vehicle; and a second controlling device for changing the compression ratio in at least one portion of a case where the operating state is changed.

Abstract: A method of operating an internal combustion engine includes moving an exhaust valve to a first open position to enable an exhaust product to flow through an exhaust port of the internal combustion engine. The method also includes maintaining the exhaust valve at the first open position for a predetermined time period. The method also includes moving an intake valve to a second open position during the predetermined time period to enable an intake product to flow through an intake port of the internal combustion engine. Additionally, the method includes preventing at least a portion of the intake product from flowing through the exhaust port during the predetermined time period with a first blocking member and a second blocking member.

Abstract: The disclosure relates to reciprocating piston engines having four cylinders with a circular cross section, cylinder axes which are parallel to one another, and an output shaft. The cylinder axes, as viewed in axial section, lie at the corner points of a rectangle that is a square, with the output shaft, which extends parallel to the cylinder axes, in the centre of the square. Each pair of cylinders which lie diagonally opposite one another are arranged in the same direction, as viewed axially, and in opposite directions, as viewed axially, with respect to the other pair of cylinders. The force or moment from each cylinder is transmitted to the output shaft via a dedicated rotating crank and a toothing system.

Abstract: An engine lubrication method is provided. The four-cycle engine has an engine block having a cylindrical bore and an enclosed oil reservoir. A crankshaft is mounted in the engine block. An oil pump driven by the cam gear, brings the oil from the oil reservoir and the valve chamber. The engine is provided with a cylinder head assembly having a pair of overhead intake and exhaust valves. A circular arc wall surrounds the web of the crankshaft at a slight distance from the web. The crankshaft web causes the oil to fly to lubricate engine parts and the oil, returns into the oil reservoir by a check valve. Flowing of oil in to the combustion chamber when the engine is oriented to incline is prevented by oil recesses and long pipes. Another lubrication and breathing system without pump is presented, wherein construction except pump is basically followed.

Abstract: Engines and processes for their operation include a compressor cylinder, at least one power cylinder, and an expander cylinder. The outlet of the compressor cylinder is fed to the inlet of a power cylinder, and the outlet of the power cylinder is fed to the expander cylinder. The compressor cylinder and the expander cylinder are operated in two-stroke fashion, and the power cylinder is operated in four-stroke fashion, all of which cylinders share a common crankshaft. Heat may be recuperated from the exhaust gas and directed to the inlet gas of the power cylinder, increasing overall efficiency.

Abstract: A method of operating an engine in a delayed exhaust engine cycle may include opening an intake valve of the engine during a first stroke to form an intake stroke. The method may further include closing the intake valve and determining an engine operating temperature. The engine operating temperature may be compared to a predetermined temperature limit. A first fuel mass may be provided to the combustion chamber between an end portion of a second stroke and a beginning portion of a third stroke. The third stroke may form a first power stroke and the intake valve and an exhaust valve in communication with the combustion chamber may be closed during the second and third strokes. The exhaust valve may be maintained in a closed position during a fourth stroke when the engine operating temperature is less than the predetermined temperature limit.

Abstract: A method of manufacturing a cylinder block for a multi-cylinder engine is disclosed herein. The cylinder block includes a crankcase and cylinder bores disposed therein separated by cylinder walls. The crankcase is adapted to receive a crankshaft and includes crank chambers disposed therein separated by partition walls. Each of the crank chambers of the crankcase corresponds to one of the cylinder bores of the cylinder block. The cylinder bore side of each partition wall has a honing runoff portion thinner in section than the crankshaft side thereof such that a step face results in the partition walls. Further, a runoff groove is formed in the partition walls of the crank chambers, and also a communication hole is formed at least partially within the runoff groove in at least one of the partition walls to enable communication between crank chambers.

Abstract: A method for designing internal combustion engines can include selecting a compression ratio that produces a compression temperature just below the autoignition temperature of a fuel/air mixture, selecting a fuel equivalence ratio that produces a combustion temperature below the threshold temperature at which NOx formation or autoignition of the mixture occurs, and selecting an expansion ratio greater than the compression ratio.

Abstract: Fuel is injected into and through the exhaust port and into the cylinder of the piston engine during the time when the flow is reversed from the normally expected flow. The engine is able to operate with some or all of its fuel injected backwards of conventional expectations. In another embodiment the fuel is injected with solid stream injector sprays directed against exhaust valves and ports and deflected into the piston cylinder against the flow of normally aspirated or supercharged engines. This invention can apply to gasoline or diesel cycles and four and two stroke type cycles of engine.

Abstract: The heat engine cycle for four-stroke and six-stroke engines essentially increasing their efficiency, stipulates cessation of suction of a charge before a piston of the engine reaches bottom dead center during the suction stroke and ignited in proportionally decreased volume of combustion chamber. The central angle of a sector of the cams on which their lobes are located is decreased in the inventive engine.

Abstract: A snowmobile includes a body, a steering mechanism provided in the body, a steering shaft connected with the steering mechanism for associated operation with the steering mechanism, a power steering device provided in the steering shaft, a pair of skis, and a connecting section arranged to connect the skis with the body and supporting the skis for pivotal movement in a horizontal direction about a first pivot axis in association with the steering shaft as well as for pivotal movement in the vertical direction about a second pivot axis which extends in a widthwise direction of the body. The first pivot axis is located at a more forward position than the second pivot axis in a horizontal plane which includes the second pivot axis. Each of the skis includes, in its lower surface, a straight portion extending straightly; an approach portion ahead of the straight portion and curving upward; and a keel portion protruding downward to a lower position than the straight portion and the approach portion.

Abstract: Methods for improving the efficiency of internal combustion engines are disclosed. In one embodiment, a method of improving the efficiency of an internal combustion engine comprises controlling the motion of an exhaust valve associated with a cylinder of the internal combustion engine. Camshafts and internal combustion engines configured for performing methods of the instant invention are also disclosed.

Abstract: A four-stroke engine includes a case which is comprised of a first case half and a second case half connected with each other at a parting plane which goes through centerline of a crankshaft and is perpendicular to centerline of a cylinder. A first bearing seat is divided into a first upper bearing seat half and a first lower bearing seat at the parting plane. A second bearing seat is divided into a second upper bearing seat half and a second upper bearing seat half at the parting plane. The first upper bearing scat half and the second upper bearing scat half are integrally molded on the first case half, and the first lower bearing seat half and the second lower bearing seat half are integrally molded on the second case half. An outer side surface of the first case half and a side cover form a valve-operating chamber for accommodating a valve-operating mechanism.

Abstract: An engine system and a method of operation are described. As one example, the method may include: during a first operating condition, operating a cylinder of the engine in a two stroke cycle to combust a first mixture of air and fuel, and adjusting an opening overlap between an intake poppet valve and an exhaust poppet valve of the cylinder to vary a composition of exhaust gases exhausted by the cylinder via the exhaust poppet valve; and during a second operating condition, operating a cylinder of the engine in a four stroke cycle to combust a second mixture of air and fuel, and adjusting a relative amount of fuel contained in the second mixture of air and fuel to vary the composition of exhaust gases exhausted by the cylinder via the exhaust poppet valve.

Abstract: The invention relates to a method for improving an internal combustion engine using: a) on the one hand at least one cylinder (1) functioning as a low-pressure cylinder according to a two-stroke operation, and b) on the other hand, two cylinders (2, 3) functioning as high-pressure combustion cylinders according to a four-stroke operation, the capacity displacement of each of the cylinders (2, 3) being less than that of the low-pressure cylinder (1), the combustion cylinders (2, 3) delivering alternatively their combusted gases towards the low-pressure cylinder (1) for a second expansion of the combusted gases.

Abstract: A four-stroke, piston-powered internal explosion (“IE”) engine for providing power output through a rotating crankshaft. The IE engine includes an engine block having power cylinders formed therein for receiving working pistons, bearing means for supporting the crankshaft, and a crankshaft supported within the bearing means having an output end extending outside of the engine block and a plurality of offset power cranks. The IE engine further includes connecting rods operably coupled to the power cranks and configured to transfer power from the working pistons to rotate the crankshaft, and working pistons that are received into the power cylinders and operably coupled to the power cranks. Each working piston has a head end positioned adjacent to a cylinder head to form a compression chamber and is configured to receive power from an explosion of a compressed volume of air/fuel mixture located within the compression chamber, and to transfer the received power to the connecting rods.

Abstract: A four stroke internal combustion engine has a gas reserving chamber 100 which communicates with an exhaust port 31 and is configured to reserve burned gas discharged from a combustion chamber. The burned gas flows into the gas reserving chamber 100 while an exhaust valve including a valve head 32a and a stem 32b is opened in an expansion stroke. The burned gas reserved in the gas reserving chamber 100 is discharged to the combustion chamber while the exhaust valve is opened in an intake stroke.

Abstract: In a multi-mode, 2-stroke/4-stroke internal combustion engine operation, by switching the engine stroke from 4-stroke operation to 2-stroke operation so that the combustion frequency is doubled, doubling of the engine power is achieved even at the same work output per cycle. In order to meet the demand of extremely high power, the engine operates in 4-stroke boosted SI operation transitioned from 2-stroke HCCI operation at pre-set level of power and crank speed requirements. By combining the multi-stroke (2-stroke HCCI and 4-stroke HCCI) and multi-mode operation (2-stroke HCCI and 4-stroke boosted SI operation), full load range and overall high efficiency with minimal NOx emission are achieved.

Abstract: A motorcycle having a belt type CVT and an engine unit in which an axial length of a cylinder is restricted. A body frame comprises a down frame extending vertically. The engine unit comprises a four-stroke engine, a belt type CVT, a clutch and a crank case. A cylinder is arranged rearwardly of the down frame with an axis thereof extending vertically. The clutch is provided between a secondary sheave shaft and an output shaft. The crank case is formed with an oil reservoir portion below a crank shaft to store lubricating oil. A rear end of the oil reservoir portion is rearward of a front end of a secondary sheave. An axis of the crank shaft is below an axis of the secondary sheave shaft.

Abstract: A four-stroke combustion engine is lubricated by a mixture of lubricant, fuel and air received from a rotary valve type carburetor. A cylinder of the engine houses a reciprocating piston and together they generally define a combustion chamber segregated from a generally sealed cavity which contains a mechanism for operating intake and exhaust valves communicating with the combustion chamber. Generally non-burning lubricant along with fuel-and-air enters the combustion chamber from the rotary-type carburetor and blows-by the piston into the sealed cavity through a clearance defined generally between the cylinder and piston for cooling the engine and lubricating the mechanical linkage assembly. Preferably, the sealed cavity is vented directly into a rotary throttle valve of the carburetor for controlled flow back into the engine without use of a check valve, enhanced idling characteristics of the engine and substantially reduced spit-back through the carburetor air inlet.

Abstract: To provide a four-cycle combustion engine wherein the air-fuel mixture can be smoothly passed at all times by the utilization of the reciprocating motion of the piston to effectively lubricate the valve operating mechanism and the cranking mechanism and also to allow the air-fuel mixture to be supplied into the combustion chamber with a high suction efficiency. By utilization of the reciprocating motion of the piston (9), a portion of the air-fuel mixture (M) fed from the intake passage (33) is circulated through a circulating passage made up of the valve chamber (18), the first passage (24), the crankcase chamber (7) and the second passage (41).

Abstract: There is provided a multicylinder four-cycle combustion engine, in which a communication hole is formed, to allow gases to flow smoothly form one cylinder to another so that the pumping loss occurring within the cylinders can be reduced. The combustion engine (E) includes an engine casing (EC) having defined therein a plurality of cylinders (2A to 2D), each having a cylinder bore (20A to 20D), and a crank chamber (30A to 30D) below the respective cylinder bore. A partition wall (21) separating the neighbor cylinder bores (20A, 20B; 20C, 20D) of the cylinders (2A to 2D) and the crank chambers (30A to 30D) from each other is formed with a communication hole (4). An open edge portion (4aa) of the uppermost edge (4a) thereof, which opens into the cylinder bore (20A to 20D) has a circumferentially intermediate major portion extending in a direction substantially perpendicular to the cylinder longitudinal axis (CH).

Abstract: A diesel engine (E) has a combustion chamber (C), a piston (T) movable in the chamber, air intake and exhaust valves (IV, EV), and a nozzle (N) injecting fuel into the combustion chamber. By controlling characteristics of an air-fuel mixture, emissions produced by combustion of the air-fuel mixture in the chamber are reduced to levels which satisfy the Tier 2 requirements established by the Environmental Protection Agency (EPA) for the engine. This may include controlling hydraulic flow characteristics through the nozzle, increasing the compression ratio within the combustion chamber, lowering the manifold air temperature (MAT), and retarding the start of fuel injection (SOI) within the chamber.

Abstract: A control device switches an engine between normal operation mode and special operation mode. In the normal operation mode, an independent cylinder configuration is formed to produce combustion independently in individual cylinders. In the special operation mode, a two-cylinder interconnect configuration is formed so that burned gas discharged from preceding cylinders currently in an exhaust stroke is introduced into following cylinders currently in an intake stroke through intercylinder gas channels, a lean mixture having a high air-fuel ratio is combusted in the preceding cylinders, and a mixture produced by supplying fuel to the burned gas is combusted in the following cylinders.

Abstract: A four-stroke internal combustion engine is provided that is capable of use in many power tools, including those power tools subjected to tippable applications. There is provided within an engine housing an oil reservoir and a valve chamber which independently communicate with a crank chamber. A strategically placed divider and passageway, located within the engine housing, appropriately direct lubricant within the engine housing so that the internal cavity of the engine is lubricated during use in various operating attitudes, and so that the fluid flows to and is held in the proper chambers of the engine housing during storage. There is also provided a breather arrangement for an internal combustion engine which includes a cam shaft having a hollow passageway in communication with the crank chamber and the air intake system of the engine.

Abstract: This is a high torque power, reciprocating engine. It is interchangeable between a 2-stroke and a 4-stroke by easily repositioning an idler gear. The combustion cylinder is sized to get the most complete combustion for high fuel efficiency and reduced exhaust emissions.

Abstract: A blowby gas circulation system for an engine having a crankcase and an intake system comprises an oil tank which is independently of the crankcase, a first breather chamber and second breather chamber which are integrally provided with the crankcase. The oil tank supplies engine oil reserved therein to the crankcase and introduces a first gas-liquid mixture generated in the crankcase. The first gas-liquid mixture is separated into a second gas-liquid mixture and engine oil in the oil tank. Then, the second gas-liquid mixture is sent to a first breather chamber, being separated into a third gas-liquid mixture and engine oil. The third gas-liquid mixture is sent to a second breather chamber in which the third gas-liquid mixture is separated into blowby gas and engine oil. The blowby gas is sucked into the intake system and the engine oil is returned to the crankcase.

Abstract: Four-stroke internal combustion engine with electrically operated inlet and exhaust valves (9,11) and means for supplying a homogeneous fuel/air mixture to the engine cylinders (1). The valves are controlled by a control unit (15), which, within a lower rpm range, closes the exhaust valve (11) before the piston (4) has reached its upper dead center point. Under the effect of trapped residual gas, a temperature increase is achieved, which results in compression ignition of the fuel/air mixture. The control unit (15) controls the exhaust valve (11), so that the amount of residual gases in the cylinders at the closing of the exhaust valves is greater at low loads and high rpm than at high loads and low rpm, in order to control the ignition delay in this manner.

Abstract: Disclosed is a four-cycle engine for a small watercraft comprising a fuel injector for injecting a fuel into an air-intake passage through an injection nozzle, an openable valve provided in the air-intake passage for regulating an intake amount of air into a cylinder, a fuel supply passage through which the fuel is supplied to the fuel injector, and an oil supply passage connected to the fuel supply passage through forced oil supply means, wherein a proper amount of oil can be sufficiently supplied to the fuel supply passage by the forced oil supply means during engine running, irrespective of a position of the valve in the air-intake passage, that is, the position of an oil supply port in the air-intake passage.

Abstract: An outboard motor is provided with an engine having a screw compressor which provides a pressurized charge for the combustion chambers of the engine. The screw compression has first and second screw rotors arranged to rotate about vertical axes which are parallel to the axes of a crankshaft of the engine. A bypass valve regulates the flow of air through a bypass conduit extending from an outlet passage of the screw compressor to the inlet passage of the screw compressor. A charge air cooler is used in a preferred embodiment and the bypass conduit then extends between the cold side plenum of the charge air cooler and the inlet of the compressor. The charge air cooler improves the operating efficiency of the engine and avoids overheating the air as it passes through the supercharger after flowing through the bypass conduit.

Abstract: An outboard motor is provided with an engine having a screw compressor which provides a pressurized charge for the combustion chambers of the engine. The screw compression has first and second screw rotors arranged to rotate about vertical axes which are parallel to the axes of a crankshaft of the engine. A bypass valve regulates the flow of air through a bypass conduit extending from an outlet passage of the screw compressor to the inlet passage of the screw compressor. A charge air cooler is used in a preferred embodiment and the bypass conduit then extends between the cold side plenum of the charge air cooler and the inlet of the compressor. The bypass valve is controlled by an engine control module in order to improve power output from the engine at low engine speeds while avoiding any violation of existing limits on the power of the engine at higher engine speeds.

Abstract: A four stroke engine having at least two cylinders spaced vertically relative to each other. Each cylinder includes a cylinder body having a cylinder bore extending generally horizontally. Plurality of air intake ducts are provided for connecting a common plenum chamber and respective air intake passages which extends to respective combustion chambers. Each of the air intake ducts has a generally straight section extending generally horizontally and parallel to each other. The distance between the straight sections is less than the distance between the axes of the cylinder bores. Also, in another feature, throttle body means are interposed between duct members, which are upstream components of the air intake ducts, and the intake passages for controlling the flow of air to the combustion chambers.

Abstract: The invention is directed to a mixture lubricated four-stroke engine having a cylinder and a piston which delimits a combustion chamber in the cylinder. The piston drives a crankshaft via a connecting rod with the crankshaft being journalled in a crankcase. An inlet valve and an outlet valve are provided for the combustion chamber and have respective valve members which are actuated via a valve drive assembly driven by the crankshaft. The inlet valve is connected via an intake channel to a mixture-preparation device. The valve housing is, on the one hand, connected to the crankcase and, on the other hand, is flow connected via a connecting channel to the intake channel. The crankcase is connected to the mixture-preparation device exclusively via the valve housing, the connecting channel and the intake channel. In this way, an adequate lubrication and excellent acceleration performance is ensured with a constructively simple configuration and excellent exhaust-gas quality.

Abstract: The present invention provides a small and light four-stroke cycle internal combustion engine applicable to a compact power working machine. A cylinder head is provided with an ignition plug and an exhaust port with an exhaust valve. A crankcase is fixed to the bottom of a cylinder block are to form a closed crank chamber. On the cylinder block formed are a first port and a second port which are open to a combustion chamber and are opened and closed by a piston, with the second port being communicated with the crank chamber through a communicating passage, the first port being connected to a carburetor, and an air-fuel mixture mixed with lubricating oil being supplied from the carburetor through this first port to the crank chamber.

Abstract: An engine powered hand-held power tool and engine lubrication method is provided, the power tool being intended to be carried by an operator during use. The power tool has a frame, including a handle to be grasped by the operator, an implement affixed to the frame having a rotary input member, and a small four-cycle, lightweight, internal combustion engine attached to the frame for driving the implement. The four-cycle engine has a lightweight aluminum alloy engine block having a cylindrical bore and an enclosed oil reservoir formed therein. A crankshaft is rotatably mounted in the engine block for rotation about a crankshaft axis. A piston reciprocates within the bore and is connected to the crankshaft by a connecting rod. An oil splasher driven by the crankshaft intermittently engages the oil within the enclosed oil reservoir to splash-lubricate the engine.

Abstract: A number of embodiments of vehicles such as scooters that are powered a compact, high performance, four-cycle crankcase compression supercharged internal combustion engine. The engine is provided with two throttle valves, one on the intake side and one on the compressor side, that are operated simultaneously and in the same direction under at least some conditions so as to improve throttle response. In addition, an arrangement is provided for limiting the maximum pressure in the compressor side under low throttle and low load conditions. This improves performance and ensures against seal degradation in the lubricating system.

Abstract: The operation of a distribution system of a four-stroke internal combustion engine, which has suction and exhaustion mechanisms, is based on the principle that the exhaustion mechanism, which opens during an expansion stroke and stays opened during the exhaustion stroke, stays opened also through the whole period of the combustion stroke and it closes only during the period of compression after opening of the suction mechanism.