82 GS650gl High warm idle

[spadefoot]

My bike starts reasonably well, and idles around 1500 RPM once it's warmed up enough to be off choke. However, once I get out and ride for a while and the engine gets really warmed up, my idle runs up to about 3500 and stays there.

Some searching found a thread where there was the suggestion that it could be leaky intake boots, and there was some discussion about adjusting the idle fuel mixture screws.

I'm guessing that the idle fuel mixture screws are the place to start. Any suggestions?

[skidMarkNZ]

My bike starts reasonably well, and idles around 1500 RPM once it's warmed up enough to be off choke. However, once I get out and ride for a while and the engine gets really warmed up, my idle runs up to about 3500 and stays there.

Some searching found a thread where there was the suggestion that it could be leaky intake boots, and there was some discussion about adjusting the idle fuel mixture screws.

I'm guessing that the idle fuel mixture screws are the place to start. Any suggestions?

Set idle mixture screws at 2 full turns out from full in (720 degrees) don't do them up too tight when screwing them in before you start or you will bugger the ends...

take off your seat and tank to get at them... on top of carbs on intake side...

[Steve]

My suggestion would be to start with the intake boots.

While you have the carbs off to get to the boots ... how long have you had the bike?
Do you know its history? Can you guarantee that the carbs are CLEAN?

I ask this because the best place to order the o-rings for your intake boots can also supply you with stainless allen-head screws to hold them back on (your stock ones will likely crumble when you remove them) and they can also supply you with a full set of o-rings to rebuild your carbs, all at a very reasonable price. The place? www.cycleorings.com. The proprietor is a member of this forum.

When you do get around to playing with the idle mixture screws, turn them out to somewhere between 2 and 3 turns out from lightly seated for a good baseline, then tweak them for highest idle. This adjustment is useless unless the intake boot o-rings are in good shape, though.

.

[Billy Ricks]

Classic intake leak symptoms.

[BassCliff]

Hi Mr. spadefoot,

There are several places for air intake system leaks. Usually it's the O-rings on old carb boots next to the cylinder head. It could be the airbox boots (between the carbs and the airbox). It could be that the airbox itself needs to be sealed up good.

When you are sure there are no air leaks, then we can discuss the air/fuel mixture for lean/rich conditions. Adjustments include float heights, jetting, mixture screws, etc, and depend on clean carbs and properly adjusted valve clearances.. Feel free to check my website and read up on all the usual suspects and procedures. There are no shortcuts or silver bullets. Check the "Top 10 Common Issues" in the mega-welcome.... CLICK HERE.

Thank you for your induglence,

BassCliff

[Nessism]

All those intake system rubber parts turn hard and brittle after 25 years. If the intake boots and carb o-rings are not leaking now, they will be soon if they are the originals. Performing a full carb rebuild is the first thing I do on every GS bike I get.

[spadefoot]

Wow, you can tell it's the start of the season! Posts are scrolling by so fast I didn't think I'd ever get back to my post.

The carbs are clean and rebuilt last summer. This weekend we did some work on the idle mixture screws and the idle adjustment, and it seems to be much better. I needed to wait overnight to try things from a totally cold state, but the weather has been bad since. I'll try one day this week and let everyone know how it went.

It could be an issue with the intake boot o-rings, that's the only seal I didn't replace when we did the rebuild on the carbs (forgot to order them).

Thanks for all the advice!