idle speed goes up by itself

[PAULYBOY]

after about 2 minutes idling. We got my sone modded GS450T back from college yesterday. My other post about his suddenly resurrected bike, and all the mods I did to it don't mention this, but I didn't touch the carbs, or the cable. Just rerouted the cable. The day after he took it back to school, he noticed the speed going up to about 2500-2800 by itself. Choke off, Coil mod done, throttle cable lubed, adjusted and working properly. Today, I had about an hour of free time (really, thats all I usually get on saturdays) and totally disconnected the throttle cable. Started it up, choke off, abd after about 2 minutes, sure enough the idle speed just sittitng in the driveway went back up to about 2400 rpm. When we did the hour long shakedown cruise several weeks ago, there were no problems at all withthe idling. As I stated when I did the coil mod on my 850, his bike also started, idled and responded better than it had in the 2 yeasr and 5 k miles he's put on it. Anyone have any ideas? As I said, no ones touched the carbs, the engine, or anything other than the coil mod with the relay.

[TheCafeKid]

after about 2 minutes idling. We got my sone modded GS450T back from college yesterday. My other post about his suddenly resurrected bike, and all the mods I did to it don't mention this, but I didn't touch the carbs, or the cable. Just rerouted the cable. The day after he took it back to school, he noticed the speed going up to about 2500-2800 by itself. Choke off, Coil mod done, throttle cable lubed, adjusted and working properly. Today, I had about an hour of free time (really, thats all I usually get on saturdays) and totally disconnected the throttle cable. Started it up, choke off, abd after about 2 minutes, sure enough the idle speed just sittitng in the driveway went back up to about 2400 rpm. When we did the hour long shakedown cruise several weeks ago, there were no problems at all withthe idling. As I stated when I did the coil mod on my 850, his bike also started, idled and responded better than it had in the 2 yeasr and 5 k miles he's put on it. Anyone have any ideas? As I said, no ones touched the carbs, the engine, or anything other than the coil mod with the relay.

Pauly, my lil KZ440 did that as well when it warmed up. Couple of different possibilities, but first thing i would check is the intake boot rings. Its possible as the bike warms, the gap between the head and the boot becomes larger, therefore making the idle rise. Failing that, it might be wise to break the carbs down. Could have something in there sticking when they get warm as well. Like i said, im off from work the 16-19. Im not going to be able to make the Brown County rally, so any of those days, aside from the 17th, that you'd like, I would be happy to come by and tinker round with yours and your sons. Im not an expert by any means, but i know enough to prolly help out a bit.

TCK

[Nessism]

Classic symptoms of an air leak. Number one problem with GS bikes. As Cafe said, intake boot o-rings are most common source of air leaks.

Good luck.

[PAULYBOY]

Josh, someday your gonna be a lifesaver for me, but Brian (my son) is doing a 50 mile marathon outside St. Louis on the 17th, so we'll be gone from midFriday 'til mid Sunday next weekend. Thanks anyway, I'll sheck the boots, which I'm assuming you mean the boots between the carbs and the engine? BTW, how are the stones? If you have enough pain to think Mick Jaggers comin to see ya, you know its a big stone!!!!

[PAULYBOY]

Classic symptoms of an air leak. Number one problem with GS bikes. As Cafe said, intake boot o-rings are most common source of air leaks.

Good luck.

So, here's a question to you and the TCK. If I took a bottle of something inflammable, like WD40, or soap bubbles, and squirted it around the boots, would it tell a leak by suddenly altering the idle?

[Nessism]

So, here's a question to you and the TCK. If I took a bottle of something inflammable, like WD40, or soap bubbles, and squirted it around the boots, would it tell a leak by suddenly altering the idle?

That technique is unreliable in my experience. Sometimes works, sometimes doesn't. Can't hurt to try. If the idle speed changes, you have confirmation.

[TheCafeKid]

So, here's a question to you and the TCK. If I took a bottle of something inflammable, like WD40, or soap bubbles, and squirted it around the boots, would it tell a leak by suddenly altering the idle?

WD40 will work, but carb cleaner spray or something like that will work too. If the idle changes, (some say it rises, mine bogged) you have a leak good sir Stones are feeling ok. Actually i dont feel them at all, and i havent passed them that ive seen. Which worries me a bit, because this happened to me once before. They kinda got stuck, and quit hurting cos they werent moving. Then they started again, and i was right back to the ER. Lets hope thats not the case..lol

[chuckycheese]

Soap!

Soap bubbles aren't inflammable!!!!!!8-[

[PAULYBOY]

Soap bubbles aren't inflammable!!!!!!8-[

keeeerectomundo! Pardon my punctuation. I should have asked whether to use something flammable or not, dependig on which would get better results.

[TheCafeKid]

Actually Pauly, you want something that will burn. This is why most suggest carb cleaner or the like. You dont want soap in your cylinders, and the flamability of whatever you use will help let you know you have a leak, because suddenly the idle will rise or lower (i think this has to do more with the cumbustion rate/temp of whatever is used. Carb cleaner likely has ethyr in it, so it burns quick)

[chuckycheese]

Right

keeeerectomundo! Pardon my punctuation. I should have asked whether to use something flammable or not, dependig on which would get better results.

Yeah, I can remember when gas trucks were labeled "inflammable" but those days are just about gone. I also have a dictionary, from about 1975, and "flammable" isn't even in it. I guess it became acceptable by convention.

[basic]

i found that the quick drying electrical contact cleaner works pretty well, as well as carb cleaner or starting fluid. I have a leak on mine and am ordering new carb to head boots for my 750L soon.

[PAULYBOY]

Thanks for all the replies. It stopped raining long enough this evening for me to go out with a can of carb cleaner and have a GO at it. I started the bike, let it run for about 2 minutes until I could get rid of the choke. After another 30 seconds, the idle went up and I started spraying, first around the boots connecting the airbox, one at a time, then to the intake, one at a time. No variations. Could there be some other source of vacuum leak? I kno in carburetted cars vacuum leaks will either create a stumble or a spike in the idle depending on how the vacuum is set up to act upon the fuel and air delivery to the engine.

[GSJohn]

I don't know if there is a connection or not but my bike's idle used to increase from 800 to 1500+ as it warmed up. Last week I synched the carbs and it does not do that anymore. But it does have a little stumbling going on at 2500 to 4000 RPM, dang it.

[robertbarr]

Here, re-read this:

That technique is unreliable in my experience. Sometimes works, sometimes doesn't. Can't hurt to try.

You're dealing with a bike that's about 30 years old. (I didn't find the year mentioned in this thread).

How old are the intake O-rings? If you DON'T know, then any effort OTHER THAN replacing them is wasted.

There's only one sequence that makes sense, if you want to solve this. If you want to just horse around, that's fine. Your bike. If you want this dealt with, you have to have a solidly sealed intake, clean carbs, proper valve lash and THEN a carb sync.