Walbro Corporation

George M Parrullo

Michael P Burns

A single needle diaphragm type carburetor has a throttle valve in a mixing passage with a venturi, an idle fuel nozzle downstream of the throttle valve when in its idle position, a high speed fuel nozzle preferably disposed within the venturi upstream of the throttle valve and a supplemental air bleed passage opening into the mixing passage upstream of both the idle and high speed fuel nozzles. Both the idle and high speed fuel nozzles communicate with each other through a transfer passage and are fed from the same fuel circuit controlled by a single needle valve which limits the fuel flow to them. At idle or low speed and low load engine operation air supplied by the supplemental air bleed passage is mixed with fuel supplied to the idle fuel nozzle. At wide open throttle, air from the air bleed passage is routed near the idle fuel nozzle, and mixed with the fuel supplied to the high speed nozzle. The air routed adjacent to the idle nozzle dries out, reduces or eliminates the liquid fuel adjacent thereto such that upon come down of the engine from wide open throttle to idle, there is not an excessive amount of fuel available to the idle nozzle which would cause an over rich come down. Advantageously, the carburetor is readily adjustable with the single needle valve and provides improved performance of the engine throughout its operational range.

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Caro, MI, United States of America

George M Parrullo