As the throttle is opened slightly above idle, the suction at the idle discharge hole diminishes and idle fuel-air flow is decreased. However, the increased volume of air entering the engine through the secondary venturi creates sufficient suction at the tip of the discharge jet to draw fuel from the metering well through the discharge jet.

The main jet controls the fuel delivery during the cruising range (from about one-quarter to three-quarter throttle opening). A small amount of air is admitted through the well vent jet (high speed bleeder) into the discharge jet through air bleed holes in the jet below the level of fuel in the metering well to insure a constant mixture ratio.

With atmospheric pressure on the fuel in the fuel bowl and lowered pressure at the tip of the discharge jet, the greater pressure on the fuel in the float chamber forces the fuel through the main jet and not the metering well (where the fuel is mixed with air admitted through the well vent jet) before being discharged into the air stream passing through the secondary venturi. The space between the power jet tube and the inside diameter of the discharge jet serves as the passage for the main jet fuel.

The fuel-air mixture discharged from the main discharge jet is first mixed with air in the secondary venturi before being mixed with additional air in the main venturi.