Ironhead fast idle

[Cooldean69]

1972 has extremely fast idle in neutral but when I am in first and let the clutch out about half way so I’m just about to roll the idle drops down to where it should be. If I let go of clutch so I’m rolling idle goes back up way high

Keihin butterfly carb with 80 slow and 160 main, idle screw all the way out so that doesn’t help. Mixture screw won’t slow idle will only cut out.

I’m going to check for intake leak but I’m just wondering how and why the clutch is affecting idle speed

No gauges so I’m just going by ear

[ElekVins]

Hi Cooldean69,

Welcome on CC, you should do a little intro here to start, it's great if you introduce yourself a bit :

http://www.chopcult.com/forum/showthread.php?t=96

[Down]

Letting go of the clutch puts load on your motor and the idle won't give enough fuel to keep it going like that.
Sounds like you could benefit from rebuilding your carb, if you don't have an intake leak.

[Guest]

disconnect your throttle cable from the carb and see if it starts. It might be you have kinked it or its snagging somewhere, causing your throttle to stay partly open.

If this doesnt make any difference, it sounds like an intake leak and you should inspect / replace the seals at the manifold.

[JBinNC]

The other consideration not mentioned is a bad or failing mechanical advance unit, if the motor is so equipped.

Symptom points to a vacuum leak or advance unit. Classic.

Jim

[Cooldean69]

Thanks guys