In an engine that includes a blow-by-gas returning system configured to direct blow-by gas within a crankcase to an intake system through an inside of a head cover, the intake system includes a cover intake-passage disposed at a blow-by-gas outlet of the head cover, and the cover intake-passage communicates with a blow-by-gas passage of the blow-by-gas outlet.

Internal combustion engine comprisinga first pair of cylinders which accommodate, according to a rectilinear reciprocating motion, relative first pistons operatively associated to a motor shaft rotating around a motor axis disposed in a transverse direction, perpendicular to a longitudinal running direction of an associable vehicle, a suction system comprising a filter box which delimits a suction volume which houses at least a first front suction duct and at least a first rear suction duct, respectively disposed in an advanced and retracted position in relation to an air/suction mixture inlet direction, each suction duct channelling the air/suction mixture before entering in the respective cylinders, wherein said first front and rear suction ducts are fixed and have respective mutually different lengths.

An injector arrangement structure includes an air cleaner which is arranged at a rear side of an engine for a vehicle, a rear suspension which extends vertically at the rear side of the engine, and a first injector which is attached to the air cleaner. The air cleaner includes an outlet tube configuring a clean side of the air cleaner. The rear suspension and the outlet tube overlap each other in a side view. A partition wall dividing an intake passage vertically is provided inside the outlet tube. The first injector is attached from a lower side of the outlet tube so as to inject fuel toward the partition wall.

A fuel supply apparatus for a general purpose engine includes a carburetor provided in an air intake line extending from an air cleaner to the general purpose engine, a pressure reduction connection channel connected to a float chamber of the carburetor and the air cleaner, a control valve provided in the pressure reduction connection channel, a pressure reduction pump provided in the pressure reduction connection channel and sucking the float chamber to reduce the pressure therein, an air fuel ratio sensor detecting the air fuel ratio of an exhaust gas discharged from the general purpose engine, and a control unit controlling the opening degree of the control valve based on a detection signal of the air fuel ratio sensor.

An intake device of an engine includes an air cleaner and an air flow sensor. The air cleaner includes an air filter, a cleaner case which forms a primary side space above the air filter and a secondary side space below the air filter, an inlet duct, and an outlet duct. The air flow sensor is fixed to the outlet duct. The cleaner case has a first side wall on which the inlet duct is mounted, and a second side wall which opposedly faces the first side wall. The air filter has a folded shape like bellows, and is held in the cleaner case. The second side wall has a deflecting portion which deflects air introduced from the inlet duct into a flow directed in an obliquely upward direction.

An apparatus and methods are provided for an air cleaner to be mounted onto an air inlet of an internal combustion engine. The air cleaner comprises an air filter that includes a filter medium disposed between a curved base and a cover. The curved base provides an interface between the air filter and the air inlet, and comprises a shape that provides clearance between the curved base and an electric choke installed onto a carburetor comprising the air inlet. The cover secures the air filter and the curved base to the air inlet such that an airstream is drawn through the filter medium and is conducted into the air inlet. A raised portion of the cover is configured to cooperate with the curved base to ensure a desired volume of the airstream is available to the air inlet at substantially all engine speeds.

An air pre-cleaner spin tube includes a vaned inlet section including an inlet flange, and an outer tube inlet portion including an outer wall forming a nozzle that defines a radial direction, and a longitudinal axis. Also, a central stem is disposed in the nozzle, and a plurality of vanes extends from the central stem to the outer wall.

An intake pipe includes a cylindrical pipe main body, a flange, which is provided on an end of the pipe main body in an axial direction and protrudes radially outward about an axis of the pipe main body from an outer surface of the pipe main body, and a chamber forming portion, which is located outside of the pipe main body and defines a chamber. The chamber forming portion is provided to connect the outer surface of the pipe main body and the flange to each other and is integrated with the pipe main body and the flange.

There is provided an air cleaner including: an outlet pipe through which air is discharged; an airflow meter that is inserted toward an interior of the outlet pipe through a wall of the outlet pipe; and a flow-regulating member that is formed projecting from an inner surface of the outlet pipe at a side of the airflow meter, the flow-regulating member including an edge that is formed with a peaked shape with respect to the inner surface and that runs along a direction of flow of air, a rear end that is formed at a downstream end of the edge in the direction of flow, and that is shaped cut sharply toward the inner surface and a width-narrowing portion that decreases in width in a circumferential direction of the outlet pipe on progression downstream in the direction of flow.

To optimize fuel supply of an engine with a carburetor during engine operation, a throttle opening degree detection sensor detecting a throttle opening degree and a control unit controlling a valve body variably controlling an opening degree of a fuel discharge part or a fuel supply passage based on a map are included. The map includes a plurality of sections divided based on the throttle opening degree and an opening degree of the valve body set for each section. The opening degree of the valve body set for each section is the opening degree of the valve body at which the engine rotation speed is highest in each section. The control unit controls an electric actuator driving the valve body to achieve the opening degree of the valve body set in a section to which the throttle opening degree detected by the throttle opening degree detection sensor belongs out of the plurality of sections.