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New Post. Now it Runs But strange....

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blkcorvair

Jedi Knight
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Well it was a simple fix. It seems as if my homeade chocke fabrication did not have enuf pull to open the needle and richen it out. So. Now it starts right up. I Had to open the bottom adjustment (What is this called?) to approx 3 1/4 turns to maintain idle. It idles well for a few about 10 seconds and than races for no reason for ten seconds, than idles again and races again...
 
Still got a bit of goop in the carb or an air leak?
 
Im thinking the throttle shaft may have too much play. Perhaps this is a source for an airleak. I believe I am out of carb cleaner at the moment so maybe difficult to check. The Throttle shaft has some side to side movement but very little if any play between the shaft and bushing. I suppose Ill just go find som ecarb cleaner and do a leak test.
 
The outbord side of the throttle shaft is wet with fuel after running so I have to assume air is getting in there just the same. I can wiggle it slightly. Anyone have any experiance with replacing the shaft? I have seen apt sells oversize shafts or I assume have the bushings replace. Question is a new one sells for $225. So at some point it may not be worth the machining costs. Also when I hit the throttle it breaks up alot and sputters. Also can be related to an air leak though I suppose.
 
Shafts are best replaced by some one like Joe or Hap who do it for a living.
 
Is the SU carb that you put on jetted for that setup? If not, it will be hard to tell if things are right.
Some cars will "lean surge" if the piston needle and jet are the wrong ones....no matter how much you unscrew the jet-nut (that's what it's called).

There are internet sites with "programs" to select the correct piston needle and main jet. Not sure where they are right now, but Google is you friend on this one.

A slight leak at the throttle shaft makes a big difference on a street car...but it is less critical on a racer, since you'll be running WOT most of the time anyway.
A good way to see if a carb is leaking at the throttle shaft is to spray WD-40 at the shaft bearing while the engine is running (use the "straw" to focus the spray). If the engine slows down a lot (due to the WD-40 making it's way into the manifold), the leak is significant.

Edit: The DOS-based program is here:

https://www.triumphclub.co.nz/su_carbs.html
 
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