Weber air adjusting screw set up

[cosley]

I'm trying to adjust the air adjusting screws (locked in place with a nut) I disconnected the linkage, backed off the idle screw and turned the air adjusting screws all the way in. Where should the idle mixture adjusting screw (with spring) be set (if it matters) while I'm trying to adjust the air adjusting screws.
With the everything disconnected and the idle screw backed off the motor is idling around 1000-1100 rpm.
3.4 twin plug w/46mm Webers
Harold #334

[LeafGreen]

Hi,

This is a formula that has worked for me over the years with all kinds of carburetors.

A good place to start for idle mixture screws (with spring) is two turns out from lightly seated. For the air bypass screws (with lock nut) maybe 1.5 turns from lightly seated. It's also important that the throttle blades are in the correct position in the carb body. Usually .5 - 1 turn of the idle stop screw is required for the bottom of the throttle valve to expose 1.5 - 2 holes in the group of progression holes while maintaining correct idle speed. You will have to balance timing, throttle blade angle and bypass screw position to get your idle speed and low speed driveability correct.

[davidppp]

Interesting..

I tend to follow the factory method ..which assumes the throttle plates are shut fully, acknoledges but there is variation between them due to wear and bent shafts!

The purpose therefore of the locked bleed screws is to balance the "leak" between cylinders..

This is not very eays to set on the car but can be done..let the car run, maybe speed the idel a little on hand throttle..

Take off one carb likage.
Unscrew the throttle stopm screw fully..throttle plates should now be fully closed.

unlock the bleed screws and mixture screws and trun them all fully in.

Measure air flow, set all three to match the highest flowing cylinder using the locked bleed screw..

Kind regards
David