85 gs450 idle spikes when it gets hot

[Guest]

It has me baffled. When the bike is cool or run under 5 min runs great. Then all of a sudden the idle shoots over 3k. I have adjusted the valves has great compression. cleaned carbs new boots stock air filter. Is there supposto be plugs on the idle mixture screws?. I have checked for vac leaks with starter fluid can't find any. Bike has never had and float problems and i do not see how they would change when it gets hot. I am using a portable fuel supply if you shut off the gas it does not change anything. Before idle goes crazy carb styx are so close not even worth changing I did not check when it does. Slides seem fine did the clunk test on them and were fine no resistance.

[Dave8338]

'Usually', when an engine runs faster after getting warmed up, it is a result of being lean and the most likely culprit on the GS bikes, is on the intake side. Did you sync the carbs after you cleaned them? Set the idle to highest possible with engine running and then back the idle set screw back down to 1,000~850 RPMS?

[cutlass79500]

To me i think its lean also. I will try that again tomorrow .When it was cool you could see on the guages it was not happy after about 3 min everything smoothed out and it did not gradually go up it goes from 1k to 3 to 3500 rpm instantly i would guess between 5 and 7 min. When it starts idling so high i start having issues letting out the clutch it is like it sticks on the way letting out the clutch lever out a little sticks for a sec then the lever pops out a little more and more but just on take of like the motor is getting really hot. The clutch has no slippage. But i just got the bike a short time ago after sitting so i am not sure if it had any of these problems before. Its almost like the fast idle cam popped into position. When you shut it off when its that high idle it will actually ignite the raw gas in the tail pipe from running so high.

[tom203]

Ok, new boots , but what about o-rings at boot/head interface?

[cutlass79500]

Ok, new boots , but what about o-rings at boot/head interface?

Tom it has new orings also. checked for vac leak with starting fluid.

[tom203]

Well, I'm the suspicious type! viton o-rings from cycle o-rings, right?

[cutlass79500]

Actually suzuki o rings came with the boots. Running into more problems. One of the mixture screws is stuck now moved about 1/2 went to screw it back down and the last little piece of the crew slot snapped. If you turn the other gets stuck after about 3 turns and the idle screw wont move. But tried to tap it loose with a screwdriver and the idle comes down . I have been soaking them with blaster its not penetrating.
I will make sure it works right afterwards The other works fine on adjusting does not make much difference if you screw it all the way in but does at 1.5 - 2 turns idle goes up. Gonna pull them tomorrow. get the dremmel out . Why they put ss screws in aluminum instead of brass is nuts. But i did find a set of carbs and they are on the way just in case. Got oring kits from the oring guy on here new float bowl gaskets needles and seats. So hopefully tomorrow or sunday i will be able to get them apart. I am hoping i have a tap i can carefully chase the threads with. Just in case the are buggered up down at the screw head.