81 GS650G idles fast after warming up

[BenelliSigma]

Hi guys, this is my first post, I registered after buying my first bike last Saturday which i love, seems to run great and the little riding ive done so far has been awesome. My only problem is that after spinning it around the block a time or two and getting it nice and warmed up it will jump to 2.5-3k at idle. Im thinking maybe an air leak or something of that nature but i wanted to know if any of you have any ideas. I wouldnt think anything is set wrong or messed up, the guy i bought it from really seems to know what he's doing so let me know what you think.

[tkent02]

Hi guys, this is my first post, I registered after buying my first bike last Saturday which i love, seems to run great and the little riding ive done so far has been awesome. My only problem is that after spinning it around the block a time or two and getting it nice and warmed up it will jump to 2.5-3k at idle. Im thinking maybe an air leak or something of that nature but i wanted to know if any of you have any ideas. I wouldnt think anything is set wrong or messed up, the guy i bought it from really seems to know what he's doing so let me know what you think.

Is the choke on?

[Larry D]

Welcome to the fun !!

I have to ask some questions first.
What maintenance did the seller do ? Did he clean the carbs ? Adjust anything ? etc....

Could very well be an air leak. How do the rubber boots look and feel ?
Could be your idle settings are incorrect to allow the bike to idle properly. How many turns are your idle screws turned out ?
Could be incorrect jetting....

Maybe the guy didn't know what he was doing. Which is why I like working on my own bike. I may not know anything either. But I know what under my azz at 80mph.

[BassCliff]

Greetings and Salutations!!

Hi Mr. BenelliSigma,

An air intake leak is always the first suspect with your symptoms. Check carb boots and intake O-rings, seal the airbox, etc. To help you get started, how about my "welcome thing"?

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[BenelliSigma]

the choke is only on to warm the bike up and then its pushed all the way in so i dont think thats the problem. it idles fine for a while but then it just revs. I think the guy that I bought it from knew what he was doing, he has many bikes, and most of them GS's. I believe he said he cleaned the carbs and all, went through just about everything to get it running, and its inspected and everything works which leads me to believe this is a more recent thing. Ill check for air leaks but whats the best way to do so? and dont you have to remove the carbs to adjust the idle properly? or is there another way? like i said im new to bikes. theyre extremely fun and great! Ive worked on cars my whole life but bikes are def. a diff. world.

[tkent02]

the choke is only on to warm the bike up and then its pushed all the way in so i dont think thats the problem. it idles fine for a while but then it just revs. I think the guy that I bought it from knew what he was doing, he has many bikes, and most of them GS's. I believe he said he cleaned the carbs and all, went through just about everything to get it running, and its inspected and everything works which leads me to believe this is a more recent thing. Ill check for air leaks but whats the best way to do so? and dont you have to remove the carbs to adjust the idle properly? or is there another way? like i said im new to bikes. theyre extremely fun and great! Ive worked on cars my whole life but bikes are def. a diff. world.

There's a big thumb screw under the carburetors, it adjusts the idle speed on all four carbs together. This is a throttle stop screw on the rack itself, NOT the big knob on the cam chain tensioner on the back of the cylinders. You do it while it is running, adjust it to idle at 1,000 or so after it is all warmed up.

[Larry D]

Well you're one up on me. Before I got my bike a year ago. I had little to no mechanical experience.

The search feature in the upper right of the forum pages, has many threads about the Highest RPM method. I'm pretty sure there are instructions on Cliffs MEGA site. As a matter of fact, I'd be surprised if it wasn't there.

[BassCliff]

The search feature in the upper right of the forum pages, has many threads about the Highest RPM method. I'm pretty sure there are instructions on Cliffs MEGA site. As a matter of fact, I'd be surprised if it wasn't there.

Plug Chops-Highest RPM Methods
(by Mr. tkent02 and Mr. psyguy)




Thank you for your indulgence,

BassCliff

[Nessism]

You guys are beating around the bush; 90% of the time an idle that creaps up is do to an intake leak from the Intake Pipe (boot) O-rings. It's almost certain that these O-rings will leak if they are the originals.

[BenelliSigma]

ill check it all out, i mean i can get by with it the way it is but i have a little OCD about making sure things are as perfect as i can make them.. granted someone else may be better but i have to know i did my best you know? Ill locate the adjustment screw and try that, but i still want to check for air leaks. whats the best substance to use to find the leak? water and soap? carb cleaner? Windex?

BTW thank you for your help! I didnt expect such quick replies. The guy who sold me the bike was right for turning me on to this site, I feel I can find out just about anything I need to know through here. If not its obviously on Bass's site.

[Nessism]

If you ride the bike with that air leak the engine will suck air from around the intake boot which will lean out the fuel mixture and make the engine run hot. A holed piston is not unheard of from running the bike in such a condition. The choice is yours but don't underestimate the consequences.

BTW, spraying junk around the boots has proven to be an unreliable method to detect leaks. Only thing you might try before taking off the carbs it to open the pilot screws to 3 turns or so and see if that fixes the problem.

[tkent02]

You guys are beating around the bush; 90% of the time an idle that creaps up is do to an intake leak from the Intake Pipe (boot) O-rings. It's almost certain that these O-rings will leak if they are the originals.

Pretty sure I changed out those o-rings on this bike a few months ago...

[BenelliSigma]

alright well not to sound like a complete novice or anything (though i am with bikes) but if i do have to remove the carbs how will I find the leak? whats the method?

[tkent02]

alright well not to sound like a complete novice or anything (though i am with bikes) but if i do have to remove the carbs how will I find the leak? whats the method?

Did you adjust the idle speed screw yet?

[Nessism]

Pretty sure I changed out those o-rings on this bike a few months ago...

It's easy to tell by looking at the screws.