The fuel enters through the idle metering jet (g) and mixes with air entering through the idle air bleed (u) forming an emulsion. The emulsion flows to four small discharge ports located near the throttle valve. The amount of emulsion dispensed through the lowest port is controlled by the idle mixture screw (W). The emulsion dispensed into the induction throat through the idle mixture port combines with induction air which is passing through the partly open throttle valve and atomizes into idle mixture.
The idle mixture can be leaned out by turning the adjustment screw in, and enriched by turning it out: both screws should be set approximately same.
The idle speed adjustment controls the engine idle rpm, i. e.. turning the screw clockwise increases the rpm, and turning it counterclockwise decreases rpm.
The idle system employed in this carburetor is an independent system since it draws the fuel from a point before the main jet carrier (Y). As a result, negative pressures prevailing in the induction throat have a continuous effect on the idle metering system and a certain amount of the idle mixture is fed into the induction throats at normal power settings as well.