So mcmud, if there was an air leak where the throttle shaft exits the carb, it would make it run lean not rich?
would'nt that leak cause excess air in the intake therefor increasing fuel intake making it run rich and therefor making the engine run with the air/fuel screws turned all the way in?
While the mixture screws are set closed (in), at idle, the only way the engine can receive fuel is by drawing from the transition slot.... a throttle plate that is opened too far is allowing/causing that flow.
the one spring i have is the return spring -- I don't think that is my problem. I am running wicked rich -- I checked the float and needle and cleaned the bowl. i am not understanding mcmud about your description of fuel entering from some other location inside the carb therefor making the air/fuel screws to have very very little effect when turned in or out...???
Perhaps this photo will help. On it you will see the hole in the bore that is below the plate, this is the idle mixture hole, typically you would see the tip of the mixture screw extending through it.
The slot is the enrichment/slot.
As the throttle plate sweeps past, fuel in the channel which feeds the enrichment/transition circuit is drawn to the depression in the intake.
If the throttle plate is set where any portion of this slot is exposed... it flows.
The dashed red line indicates how the plate should rest... below the slot.
What would make the carb run rich if the float/needle is not hung-up or out of adjustment?
The allowance of fuel is much greater at the enrichment slot than at the idle mixture hole while the mixture screw is trimmed to spec.
On the subject of the Power valve, this jet feeds a supplemental channel to the main circuit (boost venturis) and there is flow at that nozzle only while there is sufficient air velocity at the boosters. In order for this flow to occur you would have had to open the plates well beyond the transition slots.
If the float is stuck this would cause a taller fuel level (head) in the bowl, which would allow the boost venturis to tip in at a much lower rpm than is designed.
Still the throttle plates would need to be opened to allow enough air to pass in order to cause it.
Check on the position of the throttle plates, maybe disconnect the accelerator cable to see if it is causing the throttle lever to rest unclosed.
Possibly the idle speed screw is set too deep, back it out so that it's tip looses contact with the stop and verify that the throttle lever(that part which the accel cable/rod is attached to the throttle shaft) doesn't move more toward the closed position when rotational pressure is applied to it.
I thought that I read where you've pulled this carb in favor of another, is the carb with the issue mounted to the vehicle?