[taweste]

The bike idles fine, until I give it throttle where the engine idles very high until it comes back down on its own, which usually takes awhile, or you put a load on the engine. Any ideas?

Thanks
Tim

 

[DiamondLil]

Welcome Tim to the most wonderful HD fan place around. Don't be shy. Introduce yourself. We look forward to hearing from you.

 

[taweste]

Alright, so after some messing around, I've realized that if i lower the idle adjustment screw down to a point where the engine does not idle, the problem stops. But, the new problem is the fact that I have no idle.

I tried to adjust to the point where I get a functional idle, but as soon as the idle is there, the problem with the engine ceasing to come back down begins again. I cannot reach a happy medium, with the idle adjustment screw.

Would the idle air/fuel mixture be causing any of this?

Thanks
Tim

 

[taweste]

Its a mikuni carb.

Thanks
Tim

 

[taweste]

I am no mechanic, but I dont believe its a leak or worn parts because the hanging idle goes away if I turn the idle screw down to a point where it ceases to idle?

 

[Kainam]

In addition to what Dave suggests, if the carb has been on your bike awhile (over a year or so) clean the throttle return spring with carb cleaner.

 

[glens]

I've had carbs that have been in service a long time get the butterfly worn on the sides. This allows extra airflow, making idle speed spotty. As well, if there is any side-thrust, it can allow the butterfly shaft to shift sideways, causing it to stick open and more gradually vibrate closed if it even does.

Just throwing that out there. I don't know if that carb has direct control of a butterfly or a slide (which could also be worn).

 

[glens]

Agreed. The Makuni has a slide, not a butterfly and they're prone to leaks on older ones, as the diaphram goes bad. Causes a lean running condition, but Taweste says it's NOT the carb.

So they're CV carbs or not? You mention a diaphragm.

I don't know how it could not be the carb. If he turns the idle stop screw, allowing the slide (or whatever the throttle cables are actuating) to a lower, more precise position and this stops the problem. Whatever moving part he's adjusting is, I would guess, worn excessively at the normal idle position. Even if it's just an air bypass orifice/needle.

 

[Hawkmann]

Check your cable adjustment.

 

[xjwmx]

Alright, so after some messing around, I've realized that if i lower the idle adjustment screw down to a point where the engine does not idle, the problem stops. But, the new problem is the fact that I have no idle.

I tried to adjust to the point where I get a functional idle, but as soon as the idle is there, the problem with the engine ceasing to come back down begins again. I cannot reach a happy medium, with the idle adjustment screw.

Would the idle air/fuel mixture be causing any of this?

Thanks
Tim

I had this EXACT same problem. I found the thread here looking for a solution to it. The solution for me, after I'd tried everything else, was checking and setting the exhaust valve clearance. Problem solved. Check your valve clearances.