hanging idle - Timing?

[Guest]

My '82 GS550L -

Rebuilt carbs
replaced o-rings

idles great at 1100 until I stop at a light... then it'll sit around 2.5k (it varies)
If I use the transmission to 'bog down' the engine to 1100, it'll stay there just fine.

At a loss. Is it possible there is a timing issue? Keep in mind this bike doesn't have points, but the electronic pulser.....

[Steve]

First suspect would be an air leak, probably at the o-rings on the intake tubes. Sorry, but that involves removing the carbs, which is not a fun job on that bike.

One thing to try before you pull the carbs would be to check the pilot screw settings. Turn each one in GENTLY until it stops, counting the turns as you go in. Record that number, move to the next carb. When you are done, make sure the screws are out 3 full turns. That is likely a bit too rich, so you will have to turn the screws in SLOWLY, listening for a drop in engine speed. When you hear the drop, turn the screw back out 1/8 turn, move to the next carb. Blip the throttle to see if it has improved.

.

[jgm038]

In my experience - with mikuni CV carbs - a hanging idle is caused by a lean condition.


Like he said, Id check for vacuum leaks. In not sure what you have for mods, but you may also be jetted too lean.

[Brendan W]

As said, unlikely timing.
Air leak is the go to for starters.
I found an unusual one last month. Diaphragm was not seated right on one carb.

[alabamatom69]

I should've said timing ADVANCE, but...

First suspect would be an air leak, probably at the o-rings on the intake tubes. Sorry, but that involves removing the carbs, which is not a fun job on that bike..

Like I said. I have replaced the O-rings, and I can get the carbs off now in just a few minutes I've done it so many times. Carbs are also rebuilt. Runs great except for the idle issue. I'll continue to look for a vacuum leak.

I really don't understand why it hangs but will run fine and apparently forever at 1100 rpm if I bog the engine down to that point. It doesn't rev BACK up like I would expect a vacuum leak to cause....

[Nessism]

I should've said timing ADVANCE, but...


Like I said. I have replaced the O-rings, and I can get the carbs off now in just a few minutes I've done it so many times. Carbs are also rebuilt. Runs great except for the idle issue. I'll continue to look for a vacuum leak.

I really don't understand why it hangs but will run fine and apparently forever at 1100 rpm if I bog the engine down to that point. It doesn't rev BACK up like I would expect a vacuum leak to cause....

Did you replace the large O-rings between the head and the rubber carb holder boots?

You might want to check the Newbie Mistakes thread linked in my signature to see if anything applies...

[cowboyup3371]

Also, when was the last time the intake boots were replaced? You may have a slight crack in one that can cause issues especially if they are fairly old