Abstract: A carburetor fuel mixture adjustment assembly has a threadable holder which suppresses rotation of a needle valve body disposed within an elongated receptacle defined within a carburetor body. The threadable holder is rigidly engaged within a threading chamber of the receptacle. During assembly, the needle valve body is extended through a bore of the holder as a threading portion of the valve body rotateable cuts an interior threading groove into the threadable holder. The threadable holder is held rigidly within the threading chamber by the carburetor body. A sealing holder is disposed within the receptacle axially inward of the threadable holder and is prevented from rotating within the receptacle by the threadable holder. A stem holder portion of the sealing holder assures a needle portion of the needle valve assembly remains concentrically disposed within an outlet orifice of a fuel chamber of the receptacle.

Abstract: An acceleration fuel pump for use with a combustion engine carburetor is an integral part of the carburetor body and provides an additional flow of fuel to the fuel-and-air mixing passage of the carburetor during acceleration of the engine. The acceleration fuel pump has a plunger which inserts sealably into a cylindrical cavity carried by the body of the carburetor. During acceleration of the engine, the plunger inserts further into the cavity against the resilient force of a spring and toward a resilient check valve member causing the member to deform into a fuel feed state. A fuel passage which extends between the bottom of a fuel chamber of the carburetor and the fuel-and-air mixing passage of the carburetor is intersected by the cavity and the resilient check valve member.

Abstract: An acceleration device of a carburetor for a two cycle engine with a rotary dual valve which controls air flow through both a scavenging passage and a separate air intake passage each extending through a carburetor body. The carburetor body houses a metering fuel chamber and an air reference chamber defined by a diaphragm between them. Fuel in the metering fuel chamber is discharged through a port into the air intake passage. An acceleration pump has an actuation chamber which communicates with the scavenging passage and a pump chamber which communicates with the air reference chamber and a membrane between them. During engine acceleration the membrane is displaced by a pressure introduced into the actuation chamber to forcibly send air into the air reference chamber from the pump chamber to move, the diaphragm into the metering fuel chamber, and thereby increase the fuel delivered to the air intake passage.

Abstract: A limiter cap assembly of a carburetor for a two cycle engine restricts maximum and minimum fuel amounts. The limiter cap assembly has a first cap engaged telescopically to the end of a low speed needle valve and a second cap engaged telescopically to the end of a high speed needle valve. The first and second caps are identical, each having a first tab and a second tab. The first tab sets the maximum fuel amount by contacting the adjacent cap and the second tab sets the minimum fuel amount by also engaging the adjacent cap. The first and second tabs are axially spaced apart so as not to obstruct rotation of the adjacent cap via the adjacent tabs. A housing having a lid encompasses the first and second caps. The caps each have a plurality of projections which engage an inner edge of the lid, thereby, provisionally staging the caps to the carburetor while final needle valve adjustments are made.

Abstract: A fuel injection system injects a rich mixture of fuel-and-air directly into a cylinder of a two cycle engine through an intake port for combustion. A charge forming device of the fuel injection system carries a primary air intake passage which flows air into the crankcase of the engine, and a rich fuel-and-air mixing passage which flows the majority of fuel into the cylinder, preferably via a tuned injector tube. To control air flow through the air intake passage and simultaneously control fuel flow into the fuel-and-air mixing passage, a rotary throttle valve rotateably and axially moveably traverses both passages. A mixture of fuel and oil is drawn into the air intake passage via a fuel bleed passage only during wide open throttle conditions for lubrication of moving parts and bearings contained within the crankcase.

Abstract: A membrane fuel pump (A) is driven by the pulsating pressure of intake air of an engine. Fuel in the fuel tank (80) is supplied to a constant-pressure fuel chamber (30) through valve (22), and further to an intake passage through a fuel nozzle (16). A membrane purge pump (B) is also driven by the pulsating pressure of the intake air of the engine. A plurality of vapor reservoir chambers (62a-62c) are provided in a ceiling of the fuel chamber (30). The fuel vapor in the vapor reservoirs (62a-62c) is discharged from the fuel chamber (30) and back into the fuel tank (80) by the membrane purge pump (B).

Abstract: A two-stroke internal combustion engine having an air control arrangement which controls scavenging air flow during rapid engine acceleration to optimize the acceleration and maximum power output of the engine while maintaining low exhaust emissions from the engine. Desirably, the air control arrangement may comprise a valve that throttles the air passage to one half or less of its total flow area at a medium engine load or less and completely or fully opens at a medium engine load or more of the engine. Normally, the air control valve opens in unison with the throttle valve, but during rapid acceleration of the engine the air control valve opens later or more slowly than the throttle valve to control the supply of scavenging air to the combustion chamber of the engine thereby enhancing rapid acceleration of the engine.

Abstract: A rotary throttle valve type carburetor including an air intake passage extending through a carburetor body, a cylindrical valve chamber formed perpendicularly to the air intake passage, a throttle valve inserted into the valve chamber, and a throttle valve lever which rotates to impart rotation and axial movement to the throttle valve to thereby regulate the amount of air and fuel drawn through the carburetor. A plurality of circumferentially extending cam surfaces are formed on a bottom face of the throttle valve symmetrical with respect to the axis of the throttle valve, while tapered bores for receiving balls which are adapted to engage with the cam surfaces are formed in a bottom face of the valve chamber. The sliding engagement between the cam surfaces and balls due to rotation of the throttle valve is adapted to provide a predetermined axial movement of the throttle valve.

Abstract: An improved fuel flow control device of a diaphragm-type carburetor having a lever which can be easily coupled to a flow control valve body. The lever has a resilient portion which flexes to permit a cooperating portion of the valve body to pass thereby and into an opening in the lever. After the valve body is received in the opening, the resilient portion returns at least in part to its unflexed position to retain the valve body and prevent its separation from the lever.

Abstract: A circuit for delivering fuel into a valve chamber of a rotary throttle valve type carburetor. The fuel delivery circuit includes a fuel supply nozzle, protruding into the valve chamber and fixed at the bottom of the valve chamber to the carburetor body, and an intermediate wall. The intermediate wall is connected to the bottom of the carburetor body. The intermediate wall has a first chamber defined therein, a second chamber defined therein, and structure which cooperatively defines a first passage and a second passage therein. The first passage communicates the first chamber to the fixed end of the fuel supply nozzle, and the second passage communicates the second chamber to the first chamber. In addition, the fuel delivery circuit also includes an enclosure having a pressurized fuel chamber disposed under the intermediate wall, wherein the intermediate wall cooperatively defines a third passage that communicates the pressurized fuel chamber to the second chamber.

Abstract: A carburetor for a two stroke engine with an air passage and a separate fuel and air mixing passage in a carburetor body and the passages having an air valve and a throttle valve, respectively. A coupling connects a valve shaft of the air valve with a valve shaft of the throttle valve and has an area wherein the valves are rotatable relative to each other corresponding to a difference between an opening and closing angle of the air valve and an opening and closing angle of the throttle valve. Preferably, when the throttle valve is in an idle position, the air valve is closed and the throttle valve can be opened through at least some angle from its idle position before the air valve is moved from its closed position. Also, the air valve is preferably fully opened when the throttle valve is moved to its fully or wide open position.

Abstract: A fuel jet supporting structure for a carburetor includes a support column (5) provided with a fuel passage which introduces fuel to an air intake passage (9). The fuel passage includes a fuel passage bore (24), an air passage bore (19), a threaded bore (18) and an outlet passage (16) which has subsequently reduced diameters. A stepped portion between the threaded bore (18) and outlet passage (16) is tapered. The fuel jet body (25) has a middle portion forming an emulsion tube (26) and a downstream threaded portion (28) which engages the threaded bore (18). A downstream end (27) is tapered and abuts the tapered section in the bore to form a seal.

Abstract: A carburetor for providing a fuel and air mixture and a scavenging air supply to a two stroke internal combustion engine has a throttle valve received in a fuel and air mixing passage and connected to a throttle drive for controlling engine operation and an air valve received in an air passage and selectively operably connected to the throttle valve by a lost motion coupling. Preferably, the throttle valve and the air valve are barrel-type valves each comprising an opening formed through a shaft extending transversely through and rotatable within an associated bore of the carburetor body.

Abstract: A carburetor for a stratified type scavenging engine has a scavenging air supply passage with an air valve therein, a fuel and air mixture passage having a throttle valve therein, a diaphragm which defines a negative pressure chamber on one side and an atmospheric chamber on its other side, and a low pressure passage that communicates a venturi portion of the fuel and air mixing passage with the negative pressure chamber. The air valve is responsive to movement of the diaphragm caused by the pressure differential across it to move the air valve between open and closed positions and a spring yieldably biases the air valve towards its closed position. The air valve is not directly mechanically connected or linked to the throttle valve. Thus, when the throttle valve is rapidly opened during engine acceleration, the air valve is not immediately rapidly opened and is not significantly opened until a sufficient pressure differential exists across the diaphragm.

Abstract: A carburetor for an internal combustion engine with an accelerator fuel pump in the carburetor having a piston actuated by a cam on a throttle valve shaft and a ball between them. The axis of a pump chamber in which the piston is slidably received is offset from and eccentric to the axis of rotation of the throttle shaft so that little fuel is supplied to the operating engine by the accelerator pump as the shaft is rotated to move the throttle valve from its idle position to an intermediate position and most of the fuel supplied by the accelerator pump to the engine is delivered as the shaft is rotated to move the throttle valve from the intermediate position to its wide open throttle position.

Abstract: A construction of a fuel supply pipe with a proximal end press-fit portion formed of metal and a metering tip portion formed of synthetic resin. The metering tip portion, formed with a fuel jet therein, is telescopically connected to the proximal end press-fit portion of the fuel supply pipe to provide a stable fuel supply in a rotary throttle valve type carburetor.

Abstract: A carburetor with a main fuel jet and a throttle valve in a mixing passage and an apparatus for automatically supplying an enriched fuel and air mixture when an engine is cranked for starting and initial running of the engine upon starting. The apparatus has a mixing chamber with an air intake passage communicating with the mixing passage upstream of the throttle valve, a fuel inlet passage, and an outlet passage for the fuel and air mixture which communicates with the mixing passage downstream of the throttle valve. A valve for controlling the flow of the enriching fuel and air mixture through the outlet passage is manually movable to its opened position where it is releasably retained by an actuator mechanism operably associated with the throttle shaft for releasing and closing the valve when after the engine starts the throttle valve is initially moved from its idle position toward a full open position of the throttle valve.