Won't idle

[tomkline]

I have a 31 AA completely rebuilt engine. Can't seem to get it to idle down.
Adjusting screw isn't touching. Took carburator apart to replace a broken shaft.
It wouldn't idle before. Seems to running at about 700 to 800 rpm. I made sure that butterfly was centered before tightening the screws. It looks like the butterfly closes off the throat of the carburator ok. Anyone have any suggestions. All help appreciated. Thanks

[Mitch//pa]

ck for a vacuum leak

[jmeckel]

There is a bevel to the butterfly make sure it is installed right so that the bevel matches the throat for a tight fit. Also for the very slow, count the firing..... You will need to retard the spark. I have seen some plates that have been drilled, do not know why, but they should not be.

[BudP]

If the idling circuit is not working well, that is if the air adjustment screw needs to be turned all the way in or beyond three full turns out, the oriface in the idle jet is either too small (adjustment screw turned all the way in to get idle) or too large (adjustment screw turned beyond three turns out). Buy or make jets with flow-through ranges within specs. I get mine from Renner's Corner. Of course, start with a thoroughly cleaned carb. Tom Endy's article at the Santa Anita A's presents an excellent method cleaning the passage ways. A clean carb and correctly sized jets well eliminate the carb as the source of a poor idle.

[Brentwood Bob]

Also you need a tight fit of the throttle shaft to the upper casting on both sides. A quick verification is to use some vasoline, or chassis lube to seal off the shaft. Then rebush, or an oversize shaft, if that is verified as the culprit.
Also, the intake at the block, or the face of the top of the carb, if a zenith. If you have a tillotsin, the casting is prone to warping.

[tomkline]

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I think I found the problem, a leak at the intake, the gaskets were burnt through. Have just ordered copper gaskets.

[mshmodela]

Originally Posted by tomkline

I think I found the problem, a leak at the intake, the gaskets were burnt through. Have just ordered copper gaskets.

Great, I was wondering in reading this if one might use soap and water around the manifold connections to discover leaks?

[Mitch//pa]

there are many ways or methods to find leaks.
just a few that we use are

carb clean (if you have a show engine this may mess up the paint)

propane bottle with a hose attached to it

smoke machine

[Brentwood Bob]

no on the soapy water.

[BILL WILLIAMSON]

CHEEP STETHESCOPE, using JUST the open hose.
Bill W.

[Mitch//pa]

Originally Posted by BILL WILLIAMSON

CHEEP STETHESCOPE, using JUST the open hose.
Bill W.

what if u cant hear
would it then be better to use an alternative method

[BILL WILLIAMSON]

Originally Posted by Mitch//pa

what if u cant hear
would it then be better to use an alternative method

TRUST me, even if you can't hear good, with a $2.99 stethoscope & an open hose, you can hear a GNAT FART, a SPIDER BURP, ETC. I haven't tried it on any other critters
Which has NOTHING to do with that BIRD chirping sound, occasionally, in my LEFT ear, which I acquired after being KRAZY, for 3 weeks, from a bad reaction to FLEXERILL, a muscle relaxant! At that time, I also acquired a "FLOATER" in my LEFT EYE. The FLOATER is BROWN The "BIRD" is like a good old friend now, I call him "BRAKE SQUEEK"
Bill W???