My 74 Super won't idle or hold a speed. Compression is good, I adjusted the valves to .06 this morning, and adjusted the points. I rebuilt the carb about a week ago and still no luck. I have followed the instruction I have seen here on RAMVA, in Muir's book, and various other websites. How can I tell if my carb is bad? It fires up very quickly, and will run indefinitely as long as I keep feathering the accelerator. If I hold it in one spot, it will slowly die. If I try to let it idle, it dies. The two adjustment screws on the side have been adjusted by turning the smaller one out 2.5 to 3 turns and then fiddling with the big one to try to get an idle. Any help would be appreciated.
Help with carb trouble
Feb 03, 2004
13 Replies
I guess you meant to type .006" not .06.
The symptoms you describe are typical of a clogged idle port on the 34 PICT. As the throttle plate moves off the closed position, it uncovers
4 tiny ports (one-by-one) in the throat which supply the idle fuel. The smallest is so tiny that a speck of belly-button lint is enough to foul it. Assuming I'm right that this is your problem, they are hellish to get clean. Disassembly and then compressed air works (sometimes). Soaking in carb cleaner (maybe).I've always wanted to get a jewelers ultrasonic cleaning tank and try that........
Speedy Jim
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No. This would only affect idle and speeds just above idle. Normally you won't notice it driving. An intermittent idle cutoff solenoid (loose) will affect high speed but it won't idle at all (thinking out loud).
Tell us more about *exactly* what symptoms you get, what speed, under load, etc. Jim
Well, the rusty tank is probably a good clue. Odds are the carb is full of rust particles. Speedy Jim
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Sounds a bit like a vacume leak, too. Moving the throttle (and thus the accelerator pump) temporarily makes the air/fuel mixture rich and keep it running.
Max
Idle solenoid not functioning properly, or idle jet clogged.
The idle circyúit actually operates up to 3000rpm, not just at idle. You don't run off the main jet until higher rpms or big throttle openings.
Clean all the tiny passages with an air gun. By blowing against the normal direction of gasoline flow. Remove idle jets first, (you may have two, label them so you'll know which one was which.. they ARE different) then blow air into the tiny holes in the carb body, near the throttle butterfly.
Jan
Ah-ha! That's gotta be it!
:D
Jan
Sounds a bit like the symptoms I had with a vacuum leak. The=20 base of the carburettor, where it meets the manifold gasket had some residuals of the old gasket and would not seal properly. Could drive it, but it would not idle or maintain revs even if the throttle was open a bit.
Check the carb mounting and the manifold rubber boots. If you have rebuild the carb or taken it off, check the thing above also.
accelerator,
in article oZBTb.497$0 snipped-for-privacy@nwrddc01.gnilink.net, Shane at snipped-for-privacy@verizon.net wrote on 2/2/04 4:31 PM:
Get the engine up to full operating temp, then check to see if both sides of your heat riser tubes are too hot to touch. If not, they are blocked with carbon, and will cause just such a symptom as you describe due to 'carb icing.'
Ask me how I know (I have a 1974 SB that had exactly the same problem).
-Rich
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