tri carb idle adjustment

[kip younger]

I'm still having one heck of a time getting the center carb to idle correctly. The engine starts, and idles fast while the electric choke is functioning. Once the engine warms up, and should low to a normal idle, it drops to about 500rpm, and I can not get the rpm's up any higher. I've messed with the adjustment screws on the front of the carb, but with no change - turning them in will eventually shut the engine off... but once they are opened enough to let it run, it sticks right at 500rpms. The timing is about 9 degrees advanced... and the idle adjustment screw is as far forward (fastest idle) as possible. When working the carb by hand, it runs fine - it throttles right up. My un-intellegent guess is that the idle circuit in the carb is messed up. I've had the carb apart, and of course there's not much to this circuit. Some one told me he thought all three carbs should have idle circuits but I've never heard of that.
The front carb has a vaccum leak in it as well (although) the idle problem remains even with the front carb removed and the intake blocked). with the car running, and my hand on the carb, I can feel it sucking on my hand. I've had the carb apart, and have the butterflies as tight as possible, but can still see, just the smallest light shining past them. Do I need to replace these butterfly values? Thanks - kip younger >

[plastic fantastic]

Have you checked the floats to make sure they are adjusted properly? This may sound stupid, but does the throttle have a set screw you are overlooking?

[kip younger]

I've removed the spring from the idle speed adjustment screw, to give me more speed at idle. It now flucutates back and forth from 500 to 800 rpm's. There are no other screws on the carb but the idle mixture screws and the idle speed screw. thanks - kip