Walbro Engine Management, L.l.c.

Walbro Corporation

Paul J Dow

David D Hacker

Toshimasa Takahashi

Joseph M Graham

Hiroki Ogasawara

Tetsuya Takahashi

Giovanni Vimercati

In one presently preferred embodiment a stratified scavenging carburetor has a scavenging air passage with an air control valve and a fuel and air mixing passage with a throttle control valve, and a lost motion coupling associated with the valves to delay opening of the closed air valve until the throttle valve has partially opened from its idle position to an off idle position and preferably thereafter to open the air valve in phased relationship with the throttle valve so that the valves become wide open at substantially the same time. Preferably the coupling has reels associated with the valve and connected by a flexible cord.

Stratified scavenging carburetor

An apparatus for adjusting the air-fuel ratio of a fuel mixture to be supplied to an engine. The apparatus has a pair of needle valve bodies and a pair of receptacles formed in a main body of a carburetor for receiving the needle valve bodies. Each needle valve body has a needle and a head. The needles are axially movable relative to a respective needle orifice. The needles may be axially advanced and retracted by rotating the needle valve bodies within the receptacles to respectively decrease and increase the flow of the fuel mixture around the needles and through the orifices. To prevent tampering with the needle valve body setting, the head of the needle valve body has an unconventional shape requiring a specialized tool to rotatably adjust the needle valve body. To further prevent tampering, the head is recessed with the main body of the carburetor. A retainer is disposed in the main body of the carburetor and receives the needle valve bodies to facilitate maintaining alignment of the needle valve bodies relative to the receptacles. The retainer assures that a constant fuel calibration setting is maintained through the orifices by resisting displacement of the needles due to such factors as external forces applied to the head of the needle valve body or engine vibration.

Carburetor air-fuel mixture adjustment assembly

A self-relieving choke starting system for a carburetor of a combustion engine has an elongated cammed latch which projects radially outward from a rotating shaft of a choke valve located in an upstream region of a fuel-and-air mixing passage carried by a body of the carburetor. During a first attempt at starting a cold engine, the user manually rotates the choke valve from a spring biased open to a full choke position whereupon a cam end of the latch contacts a follower arm, which projects radially outward from a rotating shaft of a throttle valve located downstream of a venturi of the mixing passage. As the choke valve manually rotates closed, the throttle valve automatically rotates in an open direction against the biasing force of a throttle spring from a slow idle state, for normal engine operation, to a fast idle state for engine starting. Once the choke valve is in the full choke position and the throttle valve is in the fast idle position, a rich mixture of fuel-and-air will flow into the combustion chamber of the engine during the first attempt at starting the cold engine. If the first attempt should fail, the user can manually rotate the choke valve in an open direction to a half-choke position while the throttle valve is automatically maintained in the fast idle position to provide a slightly leaner mixture of the fuel-and-air to the engine for following attempts at cold starting.

Self-relieving choke starting system for a combustion engine carburetor

A carburetor with a valve assembly having a plastic cam body connected to a plastic shaft which extends into the carburetor body and a valve head press-fit into a slot formed through the plastic shaft. Desirably, the valve assembly eliminates the use of threaded fasteners and the need to swage or otherwise deform any of the components to connect them together. Desirably, the shaft and cam body are constructed and arranged to prevent relative rotation between them. This permits accurate location of the cam body on the shaft and facilitates calibration of the throttle valve assembly between its idle and wide open throttle positions. Further, the characteristics of the throttle valve assembly can be changed by simply providing a cam body having a different shape or construction with the shaft and/or valve disc being the same for a wide range of carburetors. The slot in the shaft is preferably longer than the diameter of the valve disc so that the valve disc may shift axially relative to the shaft so that it is self-centering within the fuel and air mixing passage. The valve disc can preferably also shift laterally relative to the shaft. This greatly facilitates assembly and manufacture of the throttle valve assembly by greatly increasing the tolerances with respect to the location of the valve disc on the valve shaft and of the slot.

Growing community of inventors

Cass City, MI, United States of America

Paul J Dow