High Idle about to make me say forget it

[melton1313]

I have searched the forum for my particular problem and haven't found the fix yet. When warm my 1981 gs1000 idles great. The problem is when I rev it up the idle will stay at about 2k to 3k rpm's. I run the idle down but it keeps doing it. Sometimes it will idle and all of a sudden the idle shoots up. I have sealed my air box, replaced the boots, o-rings, plugs and inspected the carburetors for any problems. I am a competent mechanic but I am completely stumped and am humbly asking for help.

[melton1313]

p.s.

I forgot to add I have synced carbs and used a colortune to check the mixture.

[hampshirehog]

Sounds like it's running fine and then running weak - classic airleak symptoms. However, you've checked that (worth checking again?) so could be float levels too low / sticking float needle, in the shut off position (unusual), poor supply from the fuel tap (weak vacuum, crimped fuel pipe etc). That's assuming it's not something daft like a trapped throttle cable.

[rkubik]

... assuming it's not something daft like a trapped throttle cable.

That will do it, too. Make sure you have enough free play in the cable - if you don't, it won't return to idle. Set the adjustment at the carb end of the cable.

[Nessism]

Idle mixture is lean. Could be an air leak or overly lean pilot screw adjustment. In my experience most GS bikes run best with the pilot screws in the 3-turns-out range. Also, if you have an aftermarket exhaust and air filter(s), the bike will run lean until you rejet.

[melton1313]

Fixed?

I haven't rode yet but I believe I fixed her. I'm not sure if this is the way I should have done it but I did anyway. I adjusted the throttle cable just on the verge of being too tight and adjusted the throttle cable at the handle almost all the way loose. I put the idle almost to where it wouldn't idle and made it idle with the throttle. When I say I made it idle with the throttle, it was just a small adjustment. I can rev it up and the she goes right back to idle speed. Hopefully this solves this problem but I still need to ride however its freezing right now and I'm not that motivated.

[jadesystem]

It sounds like an air leak. Best way to troubleshoot is to get a can of flammable WD-40 with a red tube extension. Spray all around the carb
body AND most importantly, the rubber carb boots. If it shoots-up in RPMs, you have a serious air/vacuum leak. What is happening is the WD40 is burning directly into the engine, through your air/vacuum leak.

This will also pinpoint for hairline cracks in the carb body(ies). Make
sure airbox and carbs itself are tightly sealed via the clamps. If the body
is cracked, probably could weld it to seal it. Check the rubber carb boots - if they are old and cracked, they're trashed !!

Good luck to you !@!

:-D\\/