Hey, anyone heard of this?

I've got the idle set to the point now where it chugs along at 1200 RPM, once warmed up for 10 minutes or so. So around town it's great, where I ride 20 minutes, stop, ride back.

But when I go for a longer ride (after about 30-40 minutes of continuous riding), the idle starts hanging at 3000 or so. If I feather the clutch in while stopped in 1st gear, I can get the RPMs dropped down below 1500 or so and it will drop back into the 1200 RPM idle.

Also noted that it starts getting a flat spot / sputtering at around 5000 RPM at about this point, though I'm not sure it's related.

Any idea what's going on with this thing?

No, but I am going to watch your post to see if you have any better results at figuring it out than I have. I am still searching for the answer to my problems which is almost exactly the same as you explained. The only difference, mine happens much faster.

So far, I have read about air leaks and floats and everything else without any "real" helpful suggestions.

If I find something on mine, I will definitely post here as well as my thread.

Did you do a rejet lately? Carb cleaning lately? Remove the petcock diaphragm and plug the vacuum line? Those are some things I have done which seems to have started my round of nonsense.

I also have this problem , hoping that someone will chime in with the answer, during a long ride i notice that the idle hangs around 3000 rpm, It doesnt happen all the time though.  But if i put a small load on it with the clutch it drops back to the 1200 mark, I do not have any flat spots in the throttle. Its a 03 500E

in your discription it almost sounds to me as tho you may have 1 of 2 things going on.  idles not set when the bike is fully warmed up or a choke that not opening up fully or even a thottle cable catching on something.  or i guess it could be a vac leak but it really doesnt sound like a vac leak to me. but with the sputter and flat spot at 5k i would also check your plugs for a leak condition.  your looking for coco brown on the plug if its white your lean if its black your rich.  ill check back for an update

I had this problem right after I got my valves adjusted. The idle would very slowly creep down from 3k and sometimes sit at 1800, so I went by the shop and told him, he had me start it and he reached underneath and adjusted the idle screw. Everything calmed down and haven't had a problem since. What I didn't understand was, if it was fine the first half the day, but then got worse as the day got warmer.. so weird, but it worked...

same problem.

starts fine, warms up nicely, holds 1200 rpm but after abour 20-30 mins riding engine fully warmed up it hangs at 3000-3500 rpm when in Neutral.


At lights, I usually hit the kill switch, wait for the light to turn green and start her back up. Idles at 1200 again nicely until it twist the throttle, there she goes back up to 3000 rpm.

bike needs a lot of work from sitting for so many years

1994 GS500e 6000 miles on the odometer, who knows what the previous owner did to her.

It's occured to me that at 10 minutes it isn't warmed up; the trouble is that if I set it any lower it dies when you feather the clutch out. I.e. instead of dropping to 1200 it just dies. I'd rather have the hanging idle than randomly dying in traffic.

FYI: Carb setup is 40/125/3 turns out on air screws/1 washer on an otherwise stock 1990 with 19K miles, stock airbox with OEM paper filter, stock exhaust.

Prior to the change the plugs looked good and still appear good, but haven't thrown a fresh set in since the change. All valves are in adjustment; still need to synch the carbs (I just eyeballed them on the bench).

Well it could be a few things as Josh mentioned.  First check your cables for proper functionality.  Lube/replace if necessary.  Next, check for a vacuum leak.  Make sure your carbs are correctly connected to your airbox, then spray wd-40 around the intakes while the engine is running.  If the RPMs increase, then you have a leak there.  If not, check your exhaust.  If you recently removed your exhaust, you will need to replace the crush washers/gaskets ($5.00 for a set).  You may need to tighten the bolts regardless if you have removed the exhaust or not.  If none of those things are helping, run the bike for a while and adjust the idle once it is well and truly warm (when your idle starts hanging ).  Finally, I would make sure your carbs are clean and in sync. 

I had the same problem as everyone else and lowering the idle worked for me - but after I synced the carbs and checked the cables I found that I could set the idle to 1500 and not have any issue at all (which was how I had it stock).

I'll sort through that list and see if it helps.

Where are you getting crush gaskets for $5? Parts Unlimited? Haven't seen them that cheap anywhere.

I got them at the dealership - I think that was what I payed.  Regardless, they're cheap.

I finally believe I have SOLVED my high idle and I bet you will not want to hear what I believe it is.

If you have checked everything over 3 times to make sure the float height is correct, carbs are clean, air mixture screw is set correctly for your carbs (2 turns stock, 3 turns for the K&N / Open exhaust, 40 / 150 jets), carb boots are not leaking, and carbs are synchronized as stated using some oil and 1/4" clear hose from the lumber store, I can almost bet money you have a hanging throttle cable.

I couldn't believe it myself. I wouldn't believe it because I would adjust and everything would be great then all the sudden right on it's own, it would climb straight to 3000 - 3500 and stay there. Almost as if there was some sort of vacuum leak or something.

Well tonight, I got out there in the dark and DID WORK and what I found was this. My float levels were spot on, my air screw was set at 3 turns (no exhaust and K&N, 40/150 jets.) I took the tank off, hooked up my temporary test tank, and fired it up. I let it warm up and fiddled with the idle slightly. Then, i connected the 1/4" hose to sync the carbs. (I thought I did a good job by sight but I was wrong. It was pulling harder on the right carb. (Due to valve clearance differences maybe.) Just touching that darn screw it would easily cause the sync to go the opposite way. I finally got it where I believe it is good based on what I could tell in the dark with my tube.

After that, i decided to ride around the complex a couple of times to see if my problem came back. Nada! Great! So, I started to put the tank on, restarted the bike it idled right at 1200 then like clockwork, 3500.

SO this time, I knew it had to be mechanical. I played around a little with the carb and the throttle and I got lucky and say the cable let the center section of the throttle drop and my idle was normal. I re-adjusted the cable to give as much slack when at idle and that seems to have done it.

I have all the caps on the carbs, I have it synched, and I have it adjusted. I rode all over town for about an hour and the bike ran beautifully.

So take a look at all those things. If you have leaks around the edges of the boots, you might try what I did. Take some high heat black silicone gasket in a tube and clean up the edges peeling off the loose broken plastic. The, cover the edges with a nice smooth bead / glob of silicone. Let it dry overnight and then re-install. Mine seem to be working fine and will buy you some time before you have to buy new ones.

Good luck.

Mrs. Bad Example has a bone-stock '09 GS500F.  Off the floor the moto was picky off the line, but amazing everywhere else.

Took it in for the 600 mile service; no more occasional dying off the line, but instead very little engine braking, and the aformentioned 3k-hanging-idle issue.

Turns out the shop had adjusted the idle to 1.1K cold, which translated to 1.5k warmed up and hanging idle.  I backed the full-warm idle to 1.2k-1.3k, and everything seems to be a happy compromise.  No more dogginess off the line, plus throttle-controlled engine braking for the twisties.

I had the same issues after adjusting my idle while the bike was still cold... lowered the idle and it stopped.