High idle when hot

[thessler]

Hi
After riding this bike and trying to work out some bugs, my biggest problem at this time is when it gets hot it will stay at 3,000 RPM or above.
After reading everything I could find on the net, i'm thinking it sounds like a faulty advance unit or dirty hopefully.
My question is for a 1984 does this have a mechanical advance or is it electronic ?

After reading about faulty advances I can not find info on what years they covered, if it is just with a point set up or also with non point or electronic ignition if thats the proper term.

I really believe it's not the carbs or cables or vacuume leak. I need to fix this I can't run around with the engine racing.

 Thank You, Tom

[Bob_Roller]

Most common problem for this, is performing a carb synch or adjustment with the engine not up to operating temp .

Valve clearances that are to tight will also cause this .

If the advance mechanism in the 'bean can' is stuck, you may be able to spray a light lubricant through a small oval plate that is pressed into the side of the bean can and get it freed up, if it is the cause .

Your bike has an electronic ignition system and yes this applies to your bike, the advance mechanism is mechanical on all of the airhead bikes from the factory regardless if it has contact breaker points, or electronic ignition .

[thessler]

Thanks Bob
I have not synch the carbs yet, the engine is just not stable enough to get a meaningfull synch. I never know where the idle is going to be.

Just checked and adjusted the valves and I am sure they are spot on.
Cables are checked and loose.
Now that I know it is mechanical , I will dig into that next.
This is a real runaway throttle, to sit above 3k seems more the a bad synch.
When it's cool or just warm it will idle around 1k.

Thanks, Tom

[Luca]

Tom, a timing light will tell you whether or not the mechanical advance is stuck.  If you have access to one I'd use a timing light on the bike while the idle is problematic before you mess with the bean can.

Somebody suggested in your other post that they had a problem like this with weak enrichener (choke) return springs.  Have you tried pushing the levers for those mechanisms down once you take the bike off choke?  A little bit of extra fuel through the enrichener or idle circuits will cause the bike idle to stay up... just like running a hot bike with a little bit of choke.  Reading a plug (cut the engine while it's running at that high idle) might give you some more insight as to whether it's fuel or electrical.

[montmil]

Next time you're sitting at a stop sign with the bike in gear, try letting the clutch out just a bit to drag the idle revs down. If they stay down when the clutch is pulled all the way back in, it's likely the advance weights needing some love.

Bean can adventures await!

[Barry]

99 times out of a hundred it's the throttle stop screws turned in too far. In the absence of a full carb tune and balance just turn out the throttle stop screws by small equal amounts. It takes 20seconds and is easily reversed if it doesn't work.

At least try the carbs settings before diving into the bean can which is a very expensive item if anything goes wrong.

[Matt Chapter]

I need to fix this I can't run around with the engine racing.

Maybe I'm in the wrong place, but isn't that the point??  ZOOOM!


As far as the high idle, seems like the rest of these "gentlemen" have covered the basics to look at.  Regarding carb sync though, I would suggest if the idle isn't stable, it isn't warmed up yet..  ride it farther and/or faster.

[montmil]

thessler wrote in a different post:

Just wanted to let you guys know, I completely disassembled the ignition can and cleaned.
I found the bigest problem seemed to be below the plate that the weights ride on it has two washers with a fiber washer between them. I think the whole plate moves with the advance and wasn't really returning with no advance.
they were dry and a little stickey, so everything got cleaned real good and a light film of grease.
Now it returns to idle fine, even when hot.
Thanks for the suggestions while trying to sort this out.

 Tom