Main Metering

The pressure drop caused by airflow past the fuel discharge nozzles causes fuel to flow from the fuel bowl, up the main well tubes, through the main metering jets and into the venturi.

The fuel flow rate is controlled by tapered metering rods inserted into the main metering jets and linked to the venturi valve. Small torsion springs are used to position the metering rods against the top of the main metering jet orifices for more precise fuel flow control. A change in throttle plate opening or engine load causes a change in venturi valve and metering rod position, providing fuel flow in proportion to airflow.

This is the only open fuel channel for stabilize (warm) engine operation. At engine start and cold run (under 23.9~C (75~F)) the cold enrichment channel will also be opening.