after bike warms up, idles high

bike runs great till it warms up, then won't idle. Carbs have been gone throw. The only way i can get the idle to drop back down is to ingauge the clutch with the front brake on and when the clutch engauges the idle will drop back to normal. I know I don't have any vacuum leaks because I used W-D 40 and sprayed the intake manifolds and the motor did not rev at all.

 

wd40 is NOT a good gaugin indicator of your problem. an unlit propane torch would be a better option, as i am NOT a guru i can only give what i have come across in my limited carb experience(doin mine now and finding out a lot of INFO HERE),but if the enrichment circuit was left intact when the carbs were cleaned then the enrichment piston seals may be leaking slightly causing this problem,due to carb cleaner deteriorating the seals.(many peeps cheat on cleanin carbs and this is a fundamental flaw when a proper break down is not done). additionally checkin the idle mixture screws located on the top of the carb next to the enrichment piston is another possibility that it was set up cold and too rich when its warm. the proper setting is 2.5 turns from bottom as a starting point. were the carbs SYNCHED UP properly with a synch stick or vacuum gauge?(synch sticks are more accurate and get it DEAD ON). that ought to just about get u started in the right direction and some others may have better idea's than me,many guru's are present and can offer better insights than me.

 

also, the idle screw between carbs 2 and 3 on the airbox side and turn it out after the bike is completely warmed up

 

Using unlit propane or starter fluid/ether on the throttle shaft seals is the next place to look. Cracked petcock vac tube? In addition to doing a running sync, did you (bother to) check your valve clearances?

Are your sparkplugs all a uniform tan color?

 

You need to make sure you do this first... I know it sounds too simple but maybe you missed it.

 

I have the exact same problem,.... still. When I get back from my trip mid/late Oct. my plan is to take the carb rack back apart, yet again :roll: and, attempt to align the carbs perfectly on the rails that hold them together. I think that another look at the butterflys might be in order also. As I recall, there is enough "wiggle room" on the butterflys that there is a distinct possibility that a 64th of an inch or less from one side to the other could cause the butterfly to hang up. I'm going to keep an eye on this post to see where it ends up because, this problem is driving me nuts too. I think that the issue is a mechanical problem rather than an air leak. I did a re-build of my carbs with all new rubber parts (except the diaphrams). All of my carb boots are in good order as well, checked and re-checked for leaks without a flaw to be found. Wiz clued me in on the fact that I might, (and did) have my carbs slightly mis-alligned. After I broke the rack apart and re-aligned the carbs there was a distinct improvement to the high idle issue I was having but, there are still times that I have to bog the clutch to control the idle speed

Cheers & luck
Ken

 

Thank u guys for your in put that will help me. I do ajust the idler screw between 2 and 3 but after I take for a ride it all comes back. I do have an idea of what it is but i need to check my manual to get the lingo right, be back in a few.

 

from the good guys over at kzrider
kzrider thread

 

nice tip and a gr8 time saver headache alleviator,or dick tracy has solved another one. Awesome link Mr Wizard. thanks for the info.

 

thank u very much xj wizard, I will try that.

 

don't thank me now, you guys ain't fixed squat yet, you just have a few more things to try
now we realize that "warmed up" means at least 10 good miles, not around the block at 35

 

quote="RickCoMatic"]Hook-up a Vacuum Line to the Petcock Vacuum Port.

Place the hose to your lips and draw a Vacuum.
If you taste Fuel ... The Petcock Diaphragm Membrane is leaking.[/quote]

Rick posted this response in "as high as a kite." It came in too late for me to try last night but will give it a shot tonight. Possibility that this may be a solution here also. There seems to be an epidemic of this symptom in the forums.

 

I'm confused as to what your problem actually is. If you are simply saying that it idles high once it warms up, then turn the idle down once it is up to operating temperature after being ridden on the road under load. Not after it has been sitting in the garage getting warmed up.

If you have backed the idle screw all the way off, and the bike still runs at high idle, and you don't have an air leak, you need to synchronize the carbs because one or more of the butterflies are still open with the idle screw all the way backed off.

I had the same problem after I rebuilt my carbs, and I finally came to the realization that I had to adjust the idle after I was riding for a few minutes and it began to idle high. Before that, I was just chasing the idle with the idle adjustment screw. Go for a ride and when it gets warmed up and idling high, pull over somewhere and adjust the idle down making very small adjustments, and working the throttle between adjustments. The sweet spot can be very small and you can easily overdo it. Especially if you keep trying to adjust it before you have been riding for a little bit.

I bet I know what you are doing, and it was the same thing I was doing. I was trying to get the bike to idle too soon after letting the choke off. Since the bike wasn't truly warmed up, I was actually adjusting the idle screw too far in, so when it warmed up, it was actually too high, then I would adjust it back down but I would go too far, then I did the same when I tried starting it back up again the next day or whenever I wanted to go riding again.

It wound up being a never ending cycle, until I finally adjusted the bike hot after riding for a little while, then just accepting that I had to leave the choke on for a little while longer than I originally was.

 

Let's not neglect the fact that a high revving engine is often times fuel starved.

Check the fuel flow out of the petcock.

It can get clogged with debris from the tank, and restrict fuel flow, especially after it's warm, and at high RPMs.

Also, if you have an inline fuel filter, you have to make sure fuel flows through that filter too.

I am finding that higher RPMs were starving the carbs because I could see the air pocket increasing in the inline filter.

I am replacing that tiny filter with a high flow silk screened one.

Hope this helps,