High idle when warm (1982 GS450)

[tkent02]

I also broke the head off the bolt on the idle adjust knob. I think it's the idle adjust thing. It's on the right side of the bike, connected to the rear of the engine. It had a nut then a knob and a spring on it. I have it tightened as far as it will go now. Which is how I broke the head off the little bolt that goes through that knob.

This is the cam chain tensioner, do not run the engineor even turn it over until you find out what you did to it.

Get a manual before you ruin anything else.

[850 Combat]

On a couple of my old bikes, a sticking idle was caused by a sticky mechanical advance mechanism. The hit the kill switch thing worked on that.

Too bad about the cam tensioner. The idle speed will be attached th the carburettors and throttle cable. Not the back of the engine.

[blakebird]

I ended up replacing the o-rings on the float needle seats, and the intake o-rings as well. Got the bike buttoned back up a few days ago, with the airbox sealed against the filter element - and also the rubber end pieces under the chrome caps fitted properly. They were pinched and not sealing, but it was the pre-filter chamber and not the sealed ends of the filtered air section.

It was handy to have the carbs off so I could see clearly where the idle adjustment screw was backed off completely. All the linkages are working properly, etc.

I rebuilt the petcock, but it dribbled with the new K&L kit diaphragm.
I took it apart a few times and checked for the alignment of the little hole....verified it was assembled correctly, and it still dribbled.
It wasn't a leaker before, so I put the oem diaphragm back in, problem solved. The center o-ring on the diaphragm was in remarkably good shape for it's age (assuming it was the original innards).

Took it for a few short local rides to ensure fuel system integrity. No leaks...so I ran it to temperature and was pleased to find the high idle at temperature is 95% fixed. The only other change made during the freshening of a few rubber parts....was that the air screws seemed to be out quite a few turns when I got the bike (about 4.5, but not all were equal).

I set them to 3 turns out, and will try going in another 1/2 turn to see if it helps crisp up the off-idle response a bit.
The idle will creep from 1,000 rpms up to 1500-1800 momentarily, then return to normal. Pretty small potatoes compared to what it was doing before. The air screw might even help. The next step will be to re-synch the carbs.

I have to recalibrate my expectations after coming off my EFI FJR.