Sticks

[foxxx85]

81 gs1000 GL. Here's the issue. Starts perfect, idles at about 1200. But, once it's warm, if i rev it up say to 4k or so... instead of returning to idle it goes to about 2.5k and stays there when I left off. The same happens when I'm riding. I can return it to idle by pulling the choke all the way, but as soon as I rev it again, the same thing happens.

[Nessism]

Hey Foxx,

You have a classic vacuum leak – most likely from the intake boot O-rings. This is the no. 1 problem on GS bikes and some newbie posts this exact same question several times per week. You can get new O-rings from a dealership, or on-line source, or from cycleorings.com. Sometimes the boots themselves are leaking so judge accordingly when you take them off to do the repair.

[p_s]

This has happened to me before when the slides were not closing smoothly. If I wiggled the idle adjuster the slides would close and the idle would come down.

But if the o-rings are old I'd replace them first.

[argonsagas]

There are several possibilities.

O-rings were mentioned.

Float level in the carb bowls can lead to this, and a float check, possible adjustment would be in order.


The most probable thing, however, is the throttle cable....and also the easiest to deal with.

It can stick due to corrosion inside the sheath or because it has a kink due to improper routing.

Look at the routing of the cable : this is the easiest thing possible as it is a visual check. If there is any sharp turn in it, try and soften the angles or loosen it off completely and re-route the cable.

Inside the sheath it is possible to have a frayed cable, which will have to be replaced, or sometimes the sheath will be bad as well, and both get replaced. More likely is dirt and/or rust, and a simple solution for that is to put a few drops of oil into the upper end of the cable and let the oil move down overnight to lubricate the path.

If that works a longer term solution is to remove the inner cable, lube it with a light grease, run oil through the sheath and then put it all back together.

You can check for restriction inside the cable sheath/outer cable by loosening the cable at the carb end and then twisting the throttle as you hold onto the loose end with your fingers. It should have a free, unrestricted movement and if it sticks at all you know where your problem is.

[Nessism]

Throttle cables can bind but the probability is much lower than the intake leak. I’d go so far as to say that if the intake O-rings are not leaking, change them anyway since they will be leaking soon if they are the originals.

Regarding throttle cables, they only cost about $15 so if yours is binding, just pitch it and get a new one. My 850 has lower than stock handlebars, so I installed a Katana 550 throttle cable since it’s shorter; throttle snaps shut with more authority than before the upgrade. Good stuff.

[robertbarr]

Out-of-sync carbs will cause this. Have you recently disassembled them?

[foxxx85]

I bought this bike a few months ago. The PO had the carbs done (Cleaned...i believe) a year ago. But it was fine for a while. About a month ago, this problem just started happening. Just kind of popped up one day.

[howling60]

it's funny, i just purchased an '80 450.. for $300.. does this EXACT thing, only it's about 3-4k when it idles up. Only reason the guy was selling, is because he doesn't have the mechanical ability/knowledge to play with it... fortunately for me, I have been known to turn a wrench or six

[foxxx85]

Still messed up

This is still happening. I replaced the o-rings and gave it a shot. Idled fine warmed up great. I let off the choke and the idle was 1-1.2k. I cracked the throttle and it revved up to 4-5k. on the way down it stuck at 2.5k. I had the throttle cable checked out and it is fine. If i yank on the choke when it is stuck at 4k it will return to idle and stay there when i let off choke. Until i revv it again then sticks at 2.5k. I sprayed wd40 around the intake boots and the rev did not pick up, that means a good seal right. Could it be on the airbox side? how do i check that? Thanks.

[Nessism]

Where are the pilot screws set? Did you tweak them for the best idle?

[foxxx85]

I just changed the large idle adjustment on the back once it was warm. It idled good.... to me...

[foxxx85]

I just saw the post about out of sync carbs. I will try to find someone that can sync them for me if that is the possible issue.

[Nessism]

I just changed the large idle adjustment on the back once it was warm. It idled good.... to me...

What is this comment in reference to?

[Billy Ricks]

What is this comment in reference to?

The throttle stop it would seem.

[Nessism]

A couple of things to try…

A hanging idle means a lean mixture. Good job on changing the intake O-rings, they are very prone to leaking so that’s a good start. A lean pilot screw setting can also cause the lean mixture. Standard process is to play with these screws until you achieve the highest idle speed – should be somewhere between 2 – 3.5 turns open from lightly seated.

To sync the carbs, you can set the idle speed up to about 2000 using the throttle stop screw, and then pull one of the spark plugs off at a time and see how far the idle speed drops down. Adjust the sync so both sides fall to roughly the same idle speed. This process sounds a little barbaric but it works. Common method employed by BMW twin owners.

Hope this helps and good luck.