Abstract: An oil pump housing of an internal combustion engine flanged to a crankshaft housing, which includes, but is not limited to an oil pump housing wall. The oil pump housing has an oil collecting tray in an upper region of the oil pump housing wall. An oil return channel is integrated in the oil pump housing. An oil return channel extends from an oil inlet opening in the oil collecting tray as far as an oil outlet opening in an area below an oil pan level.

Abstract: Crankcase ventilation filter arrangements and components therefore are described. Example arrangements are described. In one, a serviceable filter cartridge includes a check valve therein, for protection during vehicle rollover. Handle arrangements are also described. An example filter cartridge is described in which media, surrounding an open interior, is positioned between first and second, opposite, end pieces. A first end piece has a projection on an opposite side from the media, the projection including framework having an upper rail supported by spaced supports. Methods of use are described.

Abstract: Otto intake-cycle controlled-air (throttled) internal combustion engines suffer from parasitic pumping losses associated with partial vacuums developed in their intake manifolds and in the cylinders above their pistons. To solve this problem, there is provided individually partitioned dry-sump crankcases dynamic pneumatic coupling pressure reduction cycle system and method that reduce the damaging parasitic effects of the differential pressure about a piston head during an intake cycle which is a source of part-load pumping-loss friction. This closed loop system includes an independent supplemental mechanical fail-safe system of a turbo-compound engine variant for pneumatic coupling of individual cylinder-crankcase volumes. It does not alter the cylinder homogeneous mixture charge integrity and stability. The system is applicable to several engine configurations, such as controlled air intake or uncontrolled air intake combustion engines, using different fuel types, either in liquid or in gazeous state.

Abstract: A sludge adhesion inhibiting structure for an internal combustion engine according to the present invention is characterized in that a sludge inhibiting layer inhibiting generation or adhesion of sludge is formed on a surface of an area inside the internal combustion engine into which oil as a liquid does not always spread and which is contacted by oil mist as a gas. Preferably, the sludge inhibiting layer is made up of a solid alkali substance. Furthermore, the sludge inhibiting layer is provided in a head cover and formed on an inner surface of an oil separator chamber separating the oil from a blow-by gas.

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: An engine assembly may include an engine structure, intake and exhaust valves, hydraulically actuated valve lift mechanisms, and a valvetrain ventilation line. The engine structure may define a combustion chamber, intake and exhaust ports in communication with the combustion chamber, a crankcase, and a valvetrain chamber isolated from the crankcase. The intake valve may be located in the intake port and the exhaust valve may be located in the exhaust port. The hydraulically actuated valve lift mechanisms may be supported on the engine structure within the valvetrain chamber and engaged with the intake and exhaust valves. The valvetrain ventilation line may be in communication with the valvetrain chamber and may provide communication between the valvetrain chamber and the intake port.

Abstract: A system for improving PCV flow of an engine is presented. The system can reduce engine oil consumption when an engine is exposed to lateral or centripetal force. In one example, the system includes a mechanically operated valve that acts to limit PCV flow.

Abstract: A chamber structure for a vehicle may include a housing, a chamber formed inside the housing and into which a blow-by gas flows, and a cooling water path which may be formed inside the housing around the chamber and through which a preheated cooling water passes.

Abstract: An engine gas-oil separator for separating oil contents in blow-by gases that are recirculated into an intake system includes a head cover, a lower plate, and a plurality of baffles. The lower plate attaches to the head cover to define a separation chamber between an upper internal surface of the head cover and a lower internal surface of the lower plate. The separation chamber includes a blow-by gas inlet, a blow-by gas outlet and at least one oil outlet. The plurality of baffles are disposed in the separation chamber between the head cover and the lower plate. The plurality of baffles, the upper internal surface and the lower internal surface define a swirling flow path through the separation chamber in a longitudinal direction between the blow-by gas inlet in the blow-by gas outlet. The plurality of baffles are also configured to direct the blow-by gases in a generally transverse direction.

Abstract: A reflux structure for blow-by gas that returns blow-by gas generated in an engine to a clean side of an air cleaner to reflux the blow-by gas to the engine, the reflux structure for blow-by gas includes: a communication pipe that has a flow path introducing the blow-by gas from the engine to the clean side of the air cleaner; and an air funnel that is mounted on the clean side of the air cleaner and introduces intake air from a dirty side into the engine, wherein the communication pipe has a discharge port formed to discharge the blow-by gas to a side closer to a bottom than to an umbrella part of the air funnel around the air funnel.

Abstract: A separator device for a system for recirculation of blow-by gases of an internal-combustion engine comprises an elongated casing defining a separation chamber with an inlet at one end, for communication with the crankcase, an outlet at the second end, for communication with the intake system of the engine, and an end wall with at least one draining sump for draining the liquid separated in the separation chamber for return of the separated liquid into the crankcase. Associated to said inlet is an open/close element with flexible flap that opens when the crankcase is in overpressure with respect to the separation chamber, whereas associated to each draining sump is a membrane open/close element that, in the aforesaid condition of overpressure, closes, whereas, when the crankcase is in negative pressure, opens, enabling return of the liquid separated and collected inside each draining sump into the crankcase.

Abstract: The invention relates to a separator (1) for a crankcase ventilation of an internal combustion engine. The separator (1) comprises at least one swirl chamber (2), which extends along a longitudinal axis (3), wherein said swirl chamber (2) has a tangential inlet for a ventilation flow (6) at an intake-side end (4) relative to the longitudinal axis (3) thereof. The swirl chamber (2) additionally has a shared outlet (8) for the ventilation flow (6) and oil (9) entrained with the ventilation flow (6) on the outlet-side end thereof opposite the intake-side end (4) relative to the longitudinal axis (3), wherein a post-separator (10) is disposed downstream of the swirl chamber (2).

Abstract: A fuel supplying apparatus is disclosed that suppresses intrusion of oil mist into a negative pressure introducing inlet of an automatic cock and that, thereby, improves the degree of freedom of disposition. The negative pressure introducing inlet of the automatic cock is connected to a crankcase through a negative pressure communication path. The automatic cock is opened by a negative pressure generated in the crankcase and, thereby, a fuel supply path is opened that is for supplying fuel from a fuel tank to an internal combustion engine. The negative pressure communication path communicates with the air cleaner through a purge path that branches from the negative pressure communication path at a halfway point of the negative pressure communication path. The point at which the purge path branches from the negative pressure communication path is set to be at the lowest position of the negative pressure communication path to be able to collect the oil mist intruding from the crankcase.

Abstract: An apparatus for anti-freezing a PCV may include a PCV chamber forming a space therein, a blow-by gas expanding in the space, an inlet connected to the PCV chamber and adapted to supply the blow-by gas to the PCV chamber, an outlet formed lower than the inlet with respect to a horizontal axis, slanted to the horizontal axis by a predetermined angle, and connected to the PCV chamber so as to exhaust the blow-by gas to a rear end of a throttle body, protruding portions formed at a front surface and a rear surface of an inner wall of the PCV chamber along an extending direction of the outlet, and guiding a condensed water at the inner wall of the PCV chamber, and a partition having plate shape and mounted along a length direction of the protruding portions at a part of the protruding portions.

Abstract: A blow-by gas collection passage (91) extends in a cylinder block (1) and a cylinder head (3). A crank chamber (61) is connected to an oil separator (92) through the blow-by gas collection passage (91). A cutout portion is formed in an upper end portion of a wall portion (97) of the blow-by gas collection passage (91), and the oil separator (92) contacts an upper surface of the cylinder head (3) to form a connection portion (98) through which the blow-by gas collection passage (91) is connected to a cam chamber (3A). Thus, new air in the cam chamber (3A) flows into the blow-by gas collection passage (91) at an inlet portion of the oil separator (92) through the connection portion (98) to dilute the blow-by gas.

Abstract: Arrangements for use in crankcase ventilation are described and shown. Included are serviceable crankcase ventilation filter cartridges which include a media pack axial drain arrangement, for preferred, efficient, operation. A crankcase ventilation filter arrangements including a housing and such a serviceable cartridge is shown. Also shown and described are methods of assembly, operation and use.

Abstract: An oil mist separator (100) for an internal combustion engine that separates an oil component in a gas, which is introduced from a crankcase of the internal combustion engine, from the gas, includes a porous filter (150) that separates, from the gas, the oil component in the gas, the porous filter (150) being provided in a passage, through which the gas passes, and being coated with a counteragent for neutralizing an acid substance.

Abstract: The invention relates to a separator for crank housing ventilation of an internal combustion engine. The separator comprises at least one vortex chamber (2) extending along a longitudinal axis (3), wherein the vortex chamber (2) comprises an inlet for a ventilation stream (6), in particular a tangential inlet, relative to the longitudinal axis (3) at an end (4) on the inlet side. The vortex chamber (2) further comprises a common outlet (8) for the ventilation stream (6) and for oil entrained along with the ventilation stream (6), said common outlet being located at the end on the outlet side of the vortex chamber opposite the end (4) on the inlet side, relative to the longitudinal axis (3). The vortex chamber (2) is enclosed in the outlet (8) area thereof by an impact absorber (9) comprising an impact base (10) and a peripheral wall (11), wherein the impact base (10) covers the outlet (8) at a distance therefrom.

Abstract: A crankcase ventilation oil mist separator system, comprising: a first separator unit, which has at least one filter body arranged in a blow-by gas path such that blow-by gas flows through the body; a second separator unit which is arranged in a bypass path that bypasses the first separator unit; and a bypass valve which opens the bypass path when a differential pressure in the first separator unit exceeds a predefined value, wherein the second separator unit is an impactor separator.

Abstract: A breather system for a crankcase of an internal combustion engine includes a gas compressor configured to elevate the pressure of crankcase blow-by gas. At least one gas-oil separator receives gas with entrained oil from the compressor, separates oil from the gas and discharges cleaned gas. The oil is re-circulated back to the crankcase. The cleaned gas is either discharged through the engine exhaust system or re-circulated back into the engine combustion air intake. A bypass conduit allows cleaned gas to be re-circulated from the gas-oil separator outlet to the compressor inlet to balance the blow-by production with the capacity of the compressor.

Abstract: A cooling structure for cooling a liquid-cooled internal combustion engine is provided where the engine includes an EGR passage interposed between an exhaust manifold structure and an inlet manifold structure of the engine. The cooling structure includes a first cooling system and a second cooling system. The first cooling system includes at least one radiator and a liquid coolant circulatable through the radiator and the internal combustion engine for cooling the internal combustion engine. A flywheel housing for the internal combustion engine is provided with at least a portion of the second cooling system.

Abstract: A method and system is provided for regenerating and cleaning an air-oil coalescer of a crankcase ventilation system of an internal combustion engine generating blowby gas in a crankcase. The coalescer coalesces oil from the blowby gas. The method and system includes regenerating and cleaning the coalescer by intermittent rotation thereof.

Abstract: An engine assembly may include an engine block, a first cylinder head, and an air intake assembly. The engine block may include a first bank defining a first set of cylinders. The first cylinder head may be fixed to the first bank and may include a first set of intake ports. The air intake assembly may include an intake air tube, a crankcase ventilation housing integrally formed with the intake air tube, and an oil separation assembly located within the crankcase ventilation housing. The intake air tube may be in communication with the first set of intake ports and an air source. The crankcase ventilation housing may have a wall at least partially defined by the intake air tube.

Abstract: A four-stroke engine for a working machine with a rod is provided, where a tool is attached to one end of the rod in a longitudinal direction and the four-stroke engine is fixed to the other end of the rod in use. The four-stroke engine includes: an oil circulation pathway; and a gas-liquid separating chamber configured to separate oil from blowby gas. The gas-liquid separating chamber includes: an inflow part into which the blowby gas is introduced from the oil circulation pathway; oil discharge parts configured to flow the oil separated from the blowby gas back to the oil circulation pathway; and a blowby gas discharge part configured to discharge the blowby gas not containing oil mist from the gas-liquid separating chamber and supplies the blowby gas to an intake passageway to a combustion chamber.

Abstract: An oil separator disposed inside a cylinder head cover of an internal combustion engine. The oil separator includes a body section defining an elongate separator chamber and having a blowby gas inlet and a blowby gas outlet. A partition wall is disposed to divide the separator chamber into an inlet chamber at side of the blowby gas inlet and an outlet chamber at side of the blowby gas outlet. The partition wall is formed with a plurality of passage holes each of which is triangular in cross-section. A collision plate is disposed inside the outlet chamber and located opposite to the passage holes of the partition wall. A slit-like opening is defined by a lower section of the collision plate and communicated with a drain section for discharging oil separated from blowby gas into a valve operating chamber.

Abstract: The invention relates to a ventilation device (19) for an internal combustion engine (1) for evacuating blow-by gas from a crankcase (3), comprising a first line (20), which is connected at the one end to the crankcase (3) and at the other end, downstream of a forced induction device (10), to a fresh-gas line (7) and contains a ventilation valve (23), and a second line (21), which is connected at the one end, upstream of the forced induction device (10), to the fresh-gas line (7) and at the other end, between the crankcase (3) and the ventilation valve (23), to the first line (20) and contains a throttle device (23).

Abstract: An engine assembly includes an engine defining a combustion chamber and a crankcase volume, and an intake assembly having an air cleaner assembly, a throttle, and an intake manifold in a series arrangement and fluidly coupled with the combustion chamber. A first and second air-oil separator may define respective first and second separator volumes, each respectively configured to extract oil from air flowing through the volume. A first conduit may fluidly couple the crankcase with the first separator volume, a second conduit may fluidly couple the intake manifold with the first separator volume; a third conduit may fluidly couple the crankcase with the second separator volume; a fourth conduit may fluidly couple the air cleaner assembly with the second separator volume; and a fifth conduit may fluidly couple the air cleaner assembly with the first separator volume.

Abstract: A blow-by treatment assembly (10) for a vehicle having an engine (22) emitting blow-by gas (18) includes a duct (16) for receiving blow-by gas from the engine. A catalyst trap (14) is disposed in fluid communication with the duct (16). The catalyst trap (14) removes hydrocarbon emissions from the blow-by gas (18). A pump (12) pumps the blow-by gas (18) through the catalyst trap (14). An outlet (32) is in fluid communication with the catalyst trap (14) for emitting the blow-by gas to either the ambient or to a tailpipe.

Abstract: An engine air management system is provided for an internal combustion engine generating blowby gas in a crankcase containing engine oil and oil aerosol. The system includes combinations of two or more of an air-oil separator, an air filter, and an acoustic silencer.

Abstract: An internal combustion engine includes a plurality of PCV ports formed internally within the engine block and the cylinder head. The PCV ports directly connect a crankcase chamber with each of a plurality of intake ports defined by the cylinder head. The blow-by gases that accumulate within the crankcase chamber are directly vented through the internal PCV ports into the intake ports.

Abstract: A rotary piston internal combustion engine of the Wankel type has a housing (1) with a two lobed epitrochoidal inner peripheral surface (14) a shaft (8) journalled in end casings (3, 4), a rotor (9) eccentrically mounted on the shaft (8) and geared to rotate at one third speed of the shaft (8) whereby working chambers (34, 35, 36) are formed between flanks of the rotor (9) and the end casings (3, 4), which chambers vary in volume as the rotor (9) rotates, the rotor (9) being cooled by a cooling medium in a generally closed cooling circuit, the medium being circulated by a circulating pump (27), via connecting passageways (20, 18) in the end casings (3, 4) and an internal passageway (21) of the rotor (9), and through an external cooling heat exchanger (24), the cooling medium being blow-by gasses from the high pressure working chambers, which gasses have leaked past the rotor side seals (26) into the rotor cooling passages.

Abstract: The present invention relates to a ventilation device (5) for ventilating a crankcase (6) of an internal combustion engine (1), particularly in a motor vehicle, comprising a ventilation line (26), which is connected at the input side to the crankcase (6) of the internal combustion engine (1) in the mounted state, and which is connected at the output side to a fresh gas line (3) feeding fresh gas to the internal combustion engine (1), a ventilation line (27), which in the mounted state is connected to the fresh gas line (3) at the input side and to the crankcase (6) at the output side. A separator (28) is arranged in the ventilation line (26) to remove pollution from the gas that is discharged from the crankcase (6) and a pressure valve (3) is arranged in the ventilation line (26) to control the gas volume discharged from the crankcase (6).

Abstract: A part of a ceiling wall (14) of a head cover (10) that opposes an intake collection chamber (51) is constituted by a concave ceiling wall (20) that defines a concave surface facing the intake collection chamber (51), and the concave ceiling wall (20) is formed with a recessed groove (21) that further recedes toward an inner side of the head cover.

Abstract: An engine assembly includes an engine structure, an intake air assembly and a crankcase ventilation line assembly. The engine structure defines a cylinder bore, an intake port in communication with the cylinder bore, and a crankcase. The air intake assembly is in communication with the intake port. The crankcase ventilation line assembly includes a fresh air line and an oil surge protection device. The fresh air line is in communication with the crankcase and the air intake assembly and provides fresh air to the crankcase. The oil surge protection device is in communication with the fresh air line and defines an oil obstruction inhibiting oil flow to the air intake assembly while allowing air flow between the crankcase and the air intake assembly.

Abstract: A device for removing a fluidic contaminant from engine oil in an internal combustion engine includes a fluid absorbing element having a mounting element and a fluid absorption media assembled into a sump of a crankcase of the internal combustion engine. A first portion of the fluid absorption media is immersed within the engine oil contained in the sump when the engine is not operating and a second portion of the fluid absorption media is exposed to ambient air contained in a head space of the crankcase. The fluid absorption media is configured to absorb a fluidic contaminant in the engine oil during a period when the engine is not operating and to desorb the absorbed fluidic contaminant.

Abstract: An oil separation apparatus may include an intake housing provided with a gas inlet for the blow-by gas to be sucked therein, a plurality of cyclone which is formed as a cone, is disposed around the intake housing, is communicated with intake housing through an intake passage and separates oil from the blow-by gas, wherein a gas exit is formed to the upper side of the cyclone for discharging the blow-by gas and an oil outlet is formed to the lower side of the cyclone for discharging the separated oil, an exhaust housing cylinder which is provided with an gas outlet, is communicated with the gas exit and discharges the blow-by gas through the gas outlet and a control unit which is disposed within the intake and exhaust housing and selectively opens the intake passages according to intake pressure of the engine.

Abstract: An engine assembly includes an engine and an intake assembly. The engine defines a combustion chamber and a crankcase, and the intake assembly includes an intake manifold in fluid communication with the combustion chamber. An air-oil separator is provided with the engine and defines a separator volume, an inlet and an outlet, where each of the inlet and outlet are in fluid communication with the separator volume. The inlet of the air-oil separator is provided in fluid communication with the crankcase, and the outlet of the air-oil separator is provided in fluid communication with the intake manifold. The air-oil separator further includes an interior surface that abuts and surrounds the separator volume, and the interior surface has a surface roughness (RA) of greater than about 75 microns.

Abstract: A system for processing PCV gases is disclosed. In one example, the system includes an oil passage solely linking an oil separator to an engine crankcase. The system can provide an oil column that provides for continuous oil return from the oil separator to the engine crankcase even during conditions of higher levels of engine vacuum.

Abstract: A vapor-liquid separating structure for an engine includes an inlet section, a discharging section, a collecting section and a vapor-liquid separating section. The inlet section is configured and arranged to take in blow-by gas from inside a valve mechanism chamber. The discharging section is configured and arranged to discharge the blow-by gas taken in through the inlet section. The collecting section is configured and arranged to collect a majority of oil entered into the vapor-liquid separating structure through the inlet section. The vapor-liquid separating section is configured and arranged to execute a vapor-liquid separation treatment with respect to the blow-by gas while guiding the blow-by gas taken in through the inlet section to the discharging section without the blow-by gas passing through the collecting section.

Abstract: An engine assembly includes an engine structure, an air intake assembly and a positive crankcase ventilation system. The engine structure defines an intake port and a crankcase. Furthermore, the air intake assembly is in communication with the intake port. The positive crankcase ventilation system includes a fresh air line, a housing and a foul air line. The fresh air line is in communication with the air intake assembly and the crankcase. The housing defines an air inlet and an air outlet with the air inlet being in communication with the crankcase and partially defined by a wall extending into an inner volume of the housing. An oil separation mechanism may be located in the housing between the air inlet and the air outlet. The foul air line is in communication with the air intake assembly and the air outlet.

Abstract: A compressor for a turbocharger is supplied with crank case ventilation (CCV) gases from the engine which is turbocharged. The CCV gases are piped into an inlet of the compressor housing which supports an insert with an MWE structure. The MWE structure comprises an outer wall and an inner wall with a gas flow passage defined between them. At high r.p.m. of the compressor impeller air flows through the passage to provide more air volume to the impeller and at low r.p.m. excess air is bled out of the passage for recirculation. The CCV gases are directed to a position upstream of an inlet to the gas flow passage where they emerge through an outlet which may be defined in the insert. The CCV gases may be supplied to the outlet via a chamber defined between the insert and the compressor housing. The arrangement provides for improved mixing of CCV gases with the incoming air and does not compromise noise reduction.

Abstract: A filter assembly (100) comprises a housing (200) and a filter cartridge (300) that incorporates crankcase pressure-regulating components. The cartridge (300) includes an end cap (330), a plunger (340), and a spring (350). When the filter cartridge (300) is installed in the housing (200), the plunger (340) interacts with a podium (224), in response to crankcase pressure, to allow or block fluid communication with the inlet chamber (111).

Abstract: Systems, methods, and computer readable storage media are described in which exhaust gas is routed to a hydrocarbon retaining device during starting, and purged to the engine intake manifold. Various alternative approaches are described for controlling operation and diagnosing degradation. Further, various interrelated configurations are described.

Abstract: An engine includes a breather conduit, an intake conduit, and an air filter assembly. The air filter assembly includes a case and a filter element. The case includes a first opening for receiving the breather conduit, and a second opening for receiving the intake conduit. The filter element includes a first aperture, a second aperture, and filter media at least partially defining an interior chamber of the filter element. The first and second apertures of the filter element are at least partially aligned with the first and second openings of the case, respectively. The filter element is positioned in the case such that the breather conduit and the intake conduit are directed to or from the interior chamber of the filter element, such that air filtered by the filter media mixes with unfiltered gases from the breather conduit in the interior chamber of the filter element prior to entering the intake conduit.

Abstract: The invention concerns a device for separating fluid particles from a gas flow, in particular from a crankcase gas flow of an internal combustion engine. A valve is provided to allow a distribution of the gas flow to at least two cyclones depending on the volumetric flow. The valve consists of a cylinder through which the gas can flow. Inside the cylinder is a piston. This piston is designed inside the cylinder with a clearance fit or provided with one or several boreholes. In case of a low gas flow and because of the tolerances or boreholes, this gas flow will be directed around the cylinder to a first cyclone. When exceeding a certain volumetric flow the piston moves inside the cylinder and opens at least one more cyclone for the gas flow to flow through.

Abstract: An engine air management system is provided for an internal combustion engine generating blowby gas in a crankcase containing engine oil and oil aerosol. The system includes combinations of two or more of an air-oil separator, an air filter, and an acoustic silencer.

Abstract: A crankcase ventilation system is provided. The crankcase ventilation system is fluidly coupled between an engine block assembly and an axially extending air inlet adapter. A crankcase vent nozzle is provided as one aspect of the system and extends into the air inlet adapter. The crankcase vent nozzle has a leading edge portion and a trailing edge portion extending radially into an axially extending flow path in the air inlet adapter. The trailing edge portion extending further into the flow path than the leading edge portion.

Abstract: A crankcase ventilation system for an internal combustion engine includes a separator and an amplifier increasing at least one of flow and pressure along the flow path through the separator to provide higher separation efficiency.

Abstract: In a cylinder head lubricating structure for an engine, in which a breather passage which guides, toward a cylinder head, gas including oil mist generated in a crank chamber by oil splashing means housed in the crank chamber so as to splash-oil in accordance with rotation of a crankshaft is formed in a crankcase, a cylinder block and the cylinder head to supply, toward the cylinder head, lubricating oil through the breather passage, a breather chamber with which an end portion, on the crank chamber side, of the breather passage communicates is formed in the crankcase, and a one-way valve preventing backflow of the oil toward the crank chamber is attached to the crankcase to be located between the crank chamber and the breather chamber. Accordingly, it is possible to supply a sufficient amount of oil to the cylinder head side even when the head difference between the crank chamber and the cylinder head is large.

Abstract: A blow-by gas introducing passage having a blow-by gas inlet port, an air-cleaner-side breather passage that extends upwardly as branched from the blow-by gas introducing passage so as to communicate with an intake system, and a case-side breather passage that extends downwardly as branched from the blow-by gas introducing passage so as to communicate with an oil chamber are provided to an inner surface of a side cover that is detachably mounted to a timing-gear chamber communicating with a crank chamber. The blow-by gas introducing passage, the air-cleaner-side breather passage, and the case-side breather passage are formed integral with the side cover.