High Idle

[monhollenj]

For some reason when my bike warms up, it revs up real high when I'm stopped behind someone w/ the clutch held in. It goes back to regular idle as I release the clutch, but sounds like it's going to blow up when I come to a stop. Could the carb boots be causing this. Mine are cracked on the outside and didn't seemed cracked all the way through when we first put everything back together. I'm going to order a new set anyway, but was wondering if this could be the problem or if I should look down another avenue?

[bikerphil]

Have you sync'd the carbs?

[monhollenj]

yeah, we bench synched them before we put them in.

[bikerphil]

Bench sync is just for getting them close so the bike will run, you really need to vacuum sync them.

[motoman]

+1 bikerphil stated.......and that includes re-setting idle mix also a couple times during the sync process.

[Spookysxs11]

another member told me that high idle is due to lean condition if your carb boots are not leaking and the carbs are guage sinked then your idle screws need to be adjusted.

[cywelchjr]

In addition to everything else, no matter how well together you think the rack is, it's likely to move a little bit between the carbs when you put them in. This changes the sync even IF it was perfect before you put them in, and this means that even if all you did was take them out and put them back in, they need to be synced.

[brcree]

Hay Mon.....it could be several things....I just finished working on a friends 81 Kawasaki kz 1100.....it was doing the same thing. I took the carb boots that are between the heads and the carbs off and resealed them. The orig. material used was all dried up and flaking off. Bike ran like a new one after the fix.....P.S. those cracks in your boots could go all the way through and cause you probs.

[monhollenj]

Thanks guys. I really appreciate all the help I receive from you all on this forum. It really helps. I will check all of these and get back to you. It may take a few though, cause I'm juggling school and funds

[SlipNot]

Whenever you have high idle issues it's due to an air/fuel mixture problem. Particularly, too much air. You have an air leak somewhere and sounds most likely from your boots. Wrap with electrical tape temporarily to see if the problem resolves and then replace them if so. Also, with the bike running spray starting fluid around the carbs, if you get a sudden idle increase you have a leak. Of course if your running pod filters avoid spraying into them.

[Gallaecus]

have you figured out the problem???? mine is doing the same thing. any touch of the throttle will send the engine to 6 thousand RPM and I have to shut it down. #2 carb is leaking when petcock to prime. so i figure..too much gas? I would think if your boots were cracked, you would get more air and less gas and not a high idle. im thinking float and valve seat problem. ?

[cywelchjr]

Originally Posted by GALLAECUS

have you figured out the problem???? mine is doing the same thing. any touch of the throttle will send the engine to 6 thousand RPM and I have to shut it down. #2 carb is leaking when petcock to prime. so i figure..too much gas? I would think if your boots were cracked, you would get more air and less gas and not a high idle. im thinking float and valve seat problem. ?

I've not seen too much gas do that myself, but I won't say it can't do that, especially since you have a clearly leaking valve/float problem. A lean issue WILL cause a hanging idle issue, a large part of the reason for it on these bikes is because it requires you to open the throttle setting at idle too much to get enough idle speed and it gives enough vacuum to the vacuum advance to keep it from retracting when you return to idle. This keeps the timing advanced which keeps the idle really high as a side affect. This is why a good sync almost always fixes this, because the idle mixture is adjusted as part of a proper sync, so with proper idle mixture, proper sync and proper idle speed, the vacuum advance drops back to 0 when you release the throttle leaving you with no advance and engine speed drops to idle as you would expect it to do.

[Bellerophon]

Originally Posted by cywelchjr

I've not seen too much gas do that myself, but I won't say it can't do that, especially since you have a clearly leaking valve/float problem. A lean issue WILL cause a hanging idle issue, a large part of the reason for it on these bikes is because it requires you to open the throttle setting at idle too much to get enough idle speed and it gives enough vacuum to the vacuum advance to keep it from retracting when you return to idle. This keeps the timing advanced which keeps the idle really high as a side affect. This is why a good sync almost always fixes this, because the idle mixture is adjusted as part of a proper sync, so with proper idle mixture, proper sync and proper idle speed, the vacuum advance drops back to 0 when you release the throttle leaving you with no advance and engine speed drops to idle as you would expect it to do.

Listen to Cy. I had the exact same problem, and did not get it corrected until a proper vacuum synch was done.

[skids]

Originally Posted by Bellerophon

Listen to Cy. I had the exact same problem, and did not get it corrected until a proper vacuum synch was done.

And back to your original question, you are spinning your wheels trying to synch the carbs if you have leaky boots, nipple caps, or vacuum hoses.

[James England]

The symptoms you describe are not due to slightly out of sync carbs. If you bench synced them, then any slight inaccuracy wouldn't cause anything like the drastic symptoms you've described. I'd say it's more likely to be an air leak from somewhere. The carb boots are deceptive though... they are double skinned and the outer skin can be cracked quite badly but the internal skin can be undamaged.