Idle just jumped to 4500

[DocGraphics]

Like the subject says, yesterday pulled up to a stop light, put in the clutch & the idle zoomed up to 4500, popped the hood & pulled linkage back to drop it down to like 3500 till I could go again.

Limped her home & took a better look. Unhooked the linkage, still 4500 (yet will still rev faster)
Moved throttle shaft, all seems normal, rotates all the way back against the idle set screw & both butterflies at bottom of carb are closing yet still idles at 4500
How does it get gas & air to rev that high with butterflies closed.

Weber 32/36 only been on her since this spring.
Did I suck a carb gasket? is it "mainlining petrol"

Anybody have any clues to whats up? Rebuild time?

TIA, Don

[majicwrench]

Glad to hear you're drivin your car!
When reving like that simple put hand/cloth something over the carb barrels and see which one is sucking too much air. Doesn't taek much to hold a throttle plate open. If not coming thru carb barrels is coming from some other huge leak that should be obvious.
Keith

[DocGraphics]

Keith, I checked where it was sucking, putting my hand over either barrel will kill the engine so it is sucking thru the carb not below it.

Everything sets it self back to 0 when the car is off, i.e. butterflies closed, linkage sitting on idle stop screw, everything moves freely, but when I fire it up ZOOOOOOM 3500 - 4500 rpms with everything in the linkage still sitting where it should be at idle (900)

I'm thinking i need to break her open & see whats up inside.
Any ideas of what the culprit could be inside?

[majicwrench]

Issue is not inside carb, but underneath with butterflies etc. Got to be pretty obvious.
Keith

[DocGraphics]

Guess I'll yank it off & see what I can find, hope its something simple.
Thanks for the help, I'll post up my findings & any more questions.

[DocGraphics]

Well Kieth you were right....again.

Took off the carb & found the secondary butterfly wasn't closing all the way, the stop screw had moved in holding it open about 1/8".
I backed that set screw off till the butterfly closed then back in till it just held it from touching the side of the bore & put on a drop of locktight.
Put the carb back on & adjusted it back to normal & she's running just fine again.

Thanks for the help!

Now back to the driving part of this episode.