Abstract: A rotary throttle valve carburetor includes a main body defining a mixing passage and a valve bore, and a throttle valve rotatably received in the valve bore to selectively open and close the mixing passage. The carburetor main body includes an integral throttle valve support extending radially inwardly relative to the valve bore adjacent to a first end of the valve bore and a second end of the valve bore is open. A throttle cable retaining portion may also be integrally formed with the carburetor main body.

Abstract: A carburetor has a throttle valve assembly with a cam member and cam surface internally arranged in a body of the carburetor. The cam member is carried by the throttle valve body and preferably has outwardly extending tabs for locking engagement within slots formed in the throttle valve body. The throttle valve body has a dust seal constructed from an elastomeric material. The dust seal has one end sized for a tight resilient fit about a boss extending upwardly from a cap of the carburetor, and another end sized for tight resilient fit about a shaft carried by the throttle valve body, and a mid-section expanded over a flange.

Abstract: A float bowl type carburetor has a fuel and air mixing passage extending therethrough, a float bowl assembly, a priming pump communicated with the float bowl assembly and a fuel supply pipe that is communicates fuel in the float bowl assembly with the fuel and air mixing passage. The priming pump is operable to deliver pressurized fluid into the float bowl assembly in the area of the fuel supply pipe. Preferably, the priming pump discharges fluid in line with the fuel supply pipe so that at least some of the fluid discharged from the priming pump flows directly into the fuel supply pipe to facilitate delivering a rich fuel and air mixture to the engine to facilitate starting the engine.

Abstract: A rotary throttle valve carburetor includes a body having a fuel and air mixing passage and a throttle valve movable between idle and wide open positions. A valve bore is increasingly aligned with the fuel and air mixing passage as the throttle valve is moved from idle toward its wide open position. A fuel metering needle is responsive to movement of the throttle valve so that the needle moves relative to the body in response to movement of the throttle valve. A fuel nozzle extends into the valve bore, is associated with the fuel metering needle, and has a fuel ejection passage with an effective flow area controlled by movement of the fuel metering needle relative to the fuel nozzle and includes a portion with a cross-sectional area that gradually increases in the direction of fuel metering needle movement corresponding to throttle valve movement toward its wide open position.

Abstract: A carburetor includes a body having a fuel and air mixing passage formed therein and an opening in fluid communication with the fuel and air mixing passage, a fuel metering assembly carried by the body and including a fuel metering diaphragm that defines at least part of a fuel chamber that is communicated with the opening, and a groove formed in the body and open to the fuel chamber. The groove communicates at one end with the opening so that fuel vapor in the groove can be moved from the fuel chamber to the fuel and air mixing passage via the groove and opening. The groove is preferably provided at least in part in a peripheral portion of the fuel chamber to guide vapor to a fuel jet as the fuel vapor moves within the fuel chamber.

Abstract: A rotary throttle valve carburetor includes an air intake passage and a throttle valve bore formed in a carburetor body, a cam disposed in the throttle valve bore, and a throttle valve disposed in the throttle valve bore so that one end engages the cam and the other end is accessible from outside the throttle valve bore for operable connection to a throttle valve lever. The carburetor may also have a cable holder with a receiving cylinder for an outer tube of a throttle valve lever cable, an insert port for an inner wire of the cable and a slit between the receiving cylinder and insert port. The slit is smaller than an end of the inner wire to prevent that end from passing through the slit. The carburetor may further include a tamper resistant fuel adjustment bolt including an anti-turning body keyed to the carburetor body and splined to the adjustment bolt after calibration of the carburetor to prevent inadvertent rotation, or user tampering with the calibrated setting.

Abstract: A starting device for a rotary throttle valve-type carburetor enables adjustment of the quantity of air and fuel delivered to an engine to facilitate the cold start of the engine. The starting device changes the position of the throttle valve prior to starting the engine to adjust the fuel and air mixture delivered to the engine as desired to facilitate starting and initial warming up of the engine.

Abstract: A stratified scavenging mechanism of a two-stroke internal combustion engine including a carburetor for supplying and controlling an air and fuel mixture to the engine, an air intake passage in which a throttle valve is disposed, an air passage provided on a scavenging air supply body, an air control valve disposed in the air passage for opening and closing the air passage, and an air valve lever operably connected to a throttle valve lever. The scavenging air supply body is carried by the carburetor. More than one air passage may be provided, and a separate air control valve is preferably provided for each air passage.

Abstract: A stratified scavenging carburetor with a lost motion coupling permits limited relative movement of a throttle valve relative to an air valve so that initial opening of the throttle valve off idle does not open the air valve to avoid diluting with scavenging air the fuel and air mixture delivered to an engine. Rotation of the throttle valve beyond a predetermined amount from idle causes a corresponding opening of the air valve to provide scavenging air to the engine. Closing a choke valve engages a lock lever with the throttle valve to move the throttle valve off idle to a start position without opening the air valve. In another embodiment, closing the choke valve prevents the air valve from opening even if the throttle valve is moved beyond where the throttle valve would cause the air valve to open if the choke valve were open. Thus, a richer than normal fuel and air mixture can be supplied to the engine during a choke-assisted start and warm-up of the engine.

Abstract: An idle fuel supply device for a carburetor has an idle air passage that communicates with an air intake passage and a fuel chamber. A passage extending from a fuel metering chamber is connected to the fuel chamber preferably via a fuel adjusting needle valve. A low speed fuel nozzle hole communicates the fuel chamber with the air intake passage in the vicinity of a throttle valve when in its idle position. A passage communicates with the fuel chamber and the idle air passage, so that fuel and air may mix in at least a portion of the idle air passage.

Abstract: A rotary throttle valve carburetor includes a body having a fuel and air mixing passage and a throttle valve moveable between idle and wide open positions. A valve bore is increasingly aligned with the fuel and air mixing passage as the throttle valve is moved from idle toward its wide open position. A fuel metering needle is responsive to movement of the throttle valve so that the needle moves relative to the body in response to movement of the throttle valve. A fuel nozzle extends into the valve bore, is associated with the fuel metering needle, and has a fuel ejection passage with an effective flow area controlled by movement of the fuel metering needle relative to the fuel nozzle and includes a portion with a cross-sectional area that gradually increases in the direction of fuel metering needle movement corresponding to throttle valve movement toward its wide open position.

Abstract: A rotary throttle valve carburetor has a fuel-and-air mixing passage which extends through a carburetor body. A cylindrical throttle chamber extends down from a top surface of the body and communicates transversely with the fuel-and-air mixing passage. A rotary throttle seats rotatably and vertically or axially movable within the chamber and through the fuel-and-air mixing passage. The rotary throttle has a bore fully communicating and longitudinally aligned with the fuel-and-air mixing passage at wide-open throttle. The rotary throttle has a throttle shaft projecting upward through the top surface of the carburetor body and through a hole of a base portion of a plastic lid plate engaged between the top surface and a metallic bracket. An upward projecting annular shoulder of the lid plate is disposed concentrically to and spaced radially apart from the throttle shaft.

Abstract: A starting device for a rotary throttle valve-type carburetor enables adjustment of the quantity of air and fuel delivered to an engine to facilitate the cold start of the engine. The starting device changes the position of the throttle valve prior to starting the engine to adjust the fuel and air mixture delivered to the engine as desired to facilitate starting and initial warming up of the engine.

Abstract: A stratified scavenging carburetor with a lost motion coupling permits limited relative movement of a throttle valve relative to an air valve so that initial opening of the throttle valve off idle does not open the air valve to avoid diluting with scavenging air the fuel and air mixture delivered to an engine. Rotation of the throttle valve beyond a predetermined amount from idle causes a corresponding opening of the air valve to provide scavenging air to the engine. Closing a choke valve engages a lock lever with the throttle valve to move the throttle valve off idle to a start position without opening the air valve. In another embodiment, closing the choke valve prevents the air valve from opening even if the throttle valve is moved beyond where the throttle valve would cause the air valve to open if the choke valve were open. Thus, a richer than normal fuel and air mixture can be supplied to the engine during a choke-assisted start and warm-up of the engine.

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: A variable venturi carburetor for a combustion engine has an uprighted cup-shaped piston head which forms an integral part of a venturi within a fuel-and-air mixing passage carried by a carburetor body, and a needle that projects rigidly downward from the head into a fuel feed passage. The position of the piston head controls air flow by adjusting the air flow cross-section of the variable venturi, and the needle simultaneously controls fuel flow into the fuel-and-air mixing passage at the venturi via obstruction of the fuel feed passage. The piston head and needle move in unison by a flexible diaphragm engaged to and disposed above the head. An atmospheric chamber is defined below the diaphragm and a vacuum chamber is defined generally above the diaphragm. A vacuum passage extends through the bottom of the head communicating between the fuel-and-air mixing passage at the venturi and the vacuum chamber.

Abstract: A diaphragm-type carburetor has a body defining at least in part an air intake passage, a fuel metering chamber that receives fuel for delivery into the air intake passage, a fuel supply passage communicating a supply of fuel with the fuel metering chamber, and a bypass passage communicating the fuel supply passage with the air intake passage to facilitate removal of air and fuel vapor from the carburetor. The bypass passage is routed around, and does not communicate directly with the fuel metering chamber. Fuel vapor or air in the carburetor is quickly led from the bypass passage to the air intake passage to prevent a large quantity or volume of fuel vapor or air from staying in or flowing to the fuel metering chamber and thereby adversely affecting the operation of the carburetor.

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 diaphragm-type carburetor has a body defining at least in part an air intake passage, a fuel metering chamber that receives fuel for delivery into the air intake passage, a fuel supply passage communicating a supply of fuel with the fuel metering chamber, and a bypass passage communicating the fuel supply passage with the air intake passage to facilitate removal of air and fuel vapor from the carburetor. The bypass passage is routed around, and does not communicate directly with the fuel metering chamber. Fuel vapor or air in the carburetor is quickly led from the bypass passage to the air intake passage to prevent a large quantity or volume of fuel vapor or air from staying in or flowing to the fuel metering chamber and thereby adversely affecting the operation of the carburetor.

Abstract: A fuel metering assembly for a diaphragm type carburetor has a fuel metering diaphragm with at least two convolutions or annular projections providing greater travel of the diaphragm and more consistent movement of the diaphragm throughout its stroke or travel. In one embodiment, the diaphragm has at least one annular projection generally U-shaped in section projecting toward a fuel metering chamber defined on one side of the diaphragm, and at least one annular projection having a generally inverted U-shape in section projecting toward an atmospheric chamber defined on the other side of the diaphragm. Preferably, the annular projections are continuously provided between the peripheral edge of the diaphragm and a central portion of the diaphragm.