Hi Bill,
Back and this is sumpin' else?
The amount of fuel mixture the engine desires is regulated by the amount
of suction at the carburetor. So it is the suction which creates the correct
fuel flow.
With a plain fuel supply this action is automatic with the mixture being attained by adjusting the amount of fuel flow with the needle valve.
The engine's correct operation is with this fuel flow so it must be mintained.
When pressure is applied to the fuel supply this increases the possible
fuel flow at the carburetor intake,. the amount of air intake remains same.
So, to create proper mixture the needed fuel flow is adjusted via the needle valve. Actually the needle is closed an amount to suit the pressure
present.
Effectively all the fuel supply and flow must do is to be sure fuel is available in the needed amount for the suction to draw from at the carb
inlet.
Will cut short and hope!~

Hal [email protected]