Rpm's issue

[ItsStone]

So after a lot of replacing old parts, sometimes twice, I finally got my '91 Gs500e running. Only problem is the rpm's. While in neutral in my garage, I crank up the rpms and they kind of hang for a moment and then slowly fall back to idle. When I'm riding it, the problem lessens (I think, this is my first bike so I'm not completely aware of how it should run) until I pull in the clutch and they'll hit 3 or 4000 rpms until I let it back out and then return to what i assume is normal range for the speed. The carbs seemed to be pretty in sync and float heights were decent. The right looked a little low but it was a quick check, just hooked up a hose to the drain and saw that they were pretty spot on to where another page on this site said they should be. I did a small clean of the carbs but nothing to deep into them, as I didn't want to mess anything up. Any advice on what could be causing this would be massively appreciated:)

[Badot]

Try richening your idle mix.

[saxij]

my 2007 gs500 is having kind of the same problem, and yesterday I found out that the right intake boot going from the carb to the cylinder has a vacuum leak.  So I ordered newer intake boots, I hope that solves the problem.  So I would check for a vacuum leak(s) 

[yamahonkawazuki]

So after a lot of replacing old parts, sometimes twice, I finally got my '91 Gs500e running. Only problem is the rpm's. While in neutral in my garage, I crank up the rpms and they kind of hang for a moment and then slowly fall back to idle. When I'm riding it, the problem lessens (I think, this is my first bike so I'm not completely aware of how it should run) until I pull in the clutch and they'll hit 3 or 4000 rpms until I let it back out and then return to what i assume is normal range for the speed. The carbs seemed to be pretty in sync and float heights were decent. The right looked a little low but it was a quick check, just hooked up a hose to the drain and saw that they were pretty spot on to where another page on this site said they should be. I did a small clean of the carbs but nothing to deep into them, as I didn't want to mess anything up. Any advice on what could be causing this would be massively appreciated:)

possibly an intake leak, but as far as cleaning carbs, get that gallon can of carb cleaner. pulling all hte rubber and plastic parts out, then soaking them for 24 hours for a THOROUGH cleaning

[saxij]

i replaced both intake boots and the same thing is happening.
Is your problem like this -->  https://www.youtube.com/watch?v=QjnVzozwNFA
and then when you ride and come to a stop the rpms just hang there right, and you play with the clutch lever to bring them down again.

[ItsStone]

Thanks for the replies! How would one go about checking for an intake leak?
@saxiJ Yes that is pretty much exactly my problem.

[wayne242]

Could you simply be forgetting to turn the chock all the way off? I forgot to do this the other day when it was cold as heck since the chock had bike idling at 1.5k. I drove with chock left on for about 15 minutes and when i clutched in for red light, the RPM's shot up to 4k. I pull off and was like  then messed with chock.

It might not be the problem, but sticking chock is possible i guess.

[saxij]

did you find out anything yet about your rpm issue? This is driving me crazy! lol

[BeerIsSoAwesome]

Thanks for the replies! How would one go about checking for an intake leak?
@saxiJ Yes that is pretty much exactly my problem.

Easiest thing in the world. Go buy a can of starting fluid.

Start the bike and take it for a ride around the block (if it's rideable) or just let it warm up in place until it's idling somewhat stably. Start on one side of the bike and spray the starting fluid right onto the outside of the seam where the carb meets the boot, before it goes into the cylinder head. You can be liberal, give it a good spray for a few seconds, and wait. If the RPMs go up, then it's sucking stuff in. Move down the line and spray it on every seam, including the boots that go from the airbox into the carbs. Then move to the other side.

https://www.youtube.com/watch?v=oKVHqCJN2LU

[rowbvp]

I had the same thing, hanging idle. What i did to fix it was, New intake boots,with some blue RV where you connect the carb to boots. and adjusted the idle mix screw,after a bench sync. Rev the throttle a little as you adjust the idle on each side.
My exhaust was also lose,by 4-5 turns,so make sure that's tight. Hope this helps.

[BeerIsSoAwesome]

So did you adjust both idle mix screws as the bike was running?

[ItsStone]

So I checked for an intake leak and it would seem that that's the culprit. The left boot definitely is leaky. Would any one have suggestions on a place to buy replacement boots?( I figure i'll just replace them all while I'm at it) The only place I could find them was bike bandit.