Unstable Idle even after replacing throttle cable can carb flange o-rings

[Mickeymoe]

So I was having a problem with the idle speed on my GS1000G randomly switching from ~1000 to 2000+RPM which made the bike hard to ride because downshifting provided no braking and the engine would be racing like crazy at stoplights. At times it would idle, other times, crazy fast.

The forum recommended replacing the carb flange o-rings, which I did yesterday, and replaced the throttle cable with a new OEM unit while I was at it. Then I took the bike out for a ride and things were no different. But after about 10 minutes the bike seemed to be dropping to the proper idle when releasing the throttle. It didn't really make sense that it would take a while for the new parts to "kick in", so I took it for another ride tonight and turns out that things are no different from the original issue before the new parts.

When the bike starts racing if I cut the idle down with the thumbwheel under the carbs and I can get it to idle but of course, it would then stall regularly, because 2000RPM was not a legitimate idle. So I just went back home and put it in the garage, disugsted.

What I DID NOTICE HOWEVER, was that when the bike started reving (for no reason), if I reached under the seat and pushed down on the carb linkages between all four carbs, I could reduce the speed to a normal idle. But when I took pressure off, it would go back to reving.

Could it be as simple as the linkage needs a good cleaning and lube? I made sure when I installed the new throttle cable that there was about 1/4" of play in the the cable before it started engaging the carbs, so it's not that the cable is too tight.

Anybody think that maybe it's just a resistance issue in the linkage the if freed up would fix the issue? I've run out of ideas and really hate riding the bike because of the damn unpredictable reving, really takes the enjoyment out of the ride.

My last attempt is going to be to take the carbs off AGAIN, blast the linkages with compressed air and Liquid Wrench the crap out of them.

Any help would be appreciated.

Thanks, Mark

 

[Nessism]

Is the bike stock or modified? Have you fully cleaned the carbs and replaced all the O-rings? Where are the pilot screws set? Vacuum carb sync?

 

[Guest]

When the bike starts racing if I cut the idle down with the thumbwheel under the carbs and I can get it to idle but of course, it would then stall regularly, because 2000RPM was not a legitimate idle. So I just went back home and put it in the garage, disugsted.

What I DID NOTICE HOWEVER, was that when the bike started reving (for no reason), if I reached under the seat and pushed down on the carb linkages between all four carbs, I could reduce the speed to a normal idle. But when I took pressure off, it would go back to reving.

Could it be as simple as the linkage needs a good cleaning and lube? I made sure when I installed the new throttle cable that there was about 1/4" of play in the the cable before it started engaging the carbs, so it's not that the cable is too tight.

Anybody think that maybe it's just a resistance issue in the linkage the if freed up would fix the issue? I've run out of ideas and really hate riding the bike because of the damn unpredictable reving, really takes the enjoyment out of the ride.

My last attempt is going to be to take the carbs off AGAIN, blast the linkages with compressed air and Liquid Wrench the crap out of them.

Any help would be appreciated.

Thanks, Mark

Did you bench sync the carbs while you had them off? You may have one of the butterflies open a bit more than the others. Borrow a vacuum gauge set and check them. If they are out, try to adjust 1-2 then 3-4 and finally 2-3.

 

[Steve]

Is there a little slack in the cable? Sounds like it's a bit too tight.

.

 

[alke46]

I agree with Steve on this one. I had a similar issue with mine and I was pretty sure the cables were set properly but after slackening them both and readjusting them I was able to get mine settled into correct positions. Sometimes we overlook or overthink the simplest things. Good luck.

 

[Mickeymoe]

"I made sure when I installed the new throttle cable that there was about 1/4" of play in the the cable before it started engaging the carbs, so it's not that the cable is too tight....."

No, the cable is not too tight, I made sure to leave slack that I could adjust out with the top adjuster at the handgrip.

Nobody commented on the linkage being sticky, anyone want to weigh in? Lastly, I don't know how to "sync" carbs. I DID replace the flange o-rings.....are there others I don't know about?

Mark

 

[Nessism]

Vacuum syncing the carbs is part of normal maintenance as described in the factory Suzuki service manual. Please review the maintenance schedule and plan to bring everything up to date as specified.

The normal maintenance schedule doesn't mention rebuilding the carbs and replacing all the 35 year old rubber so plan to do things like that too if you want the bike to be trouble free.

 

[Big T]

Mark, please go to Nessism's post above and check the Top Newbie Mistakes link. Tell us how many of those you have/haven't done.

It's unlikely that the carb linkage is sticking. But, you can easily check that by twisting the throttle and letting it go. Does it snap back? If so, no sticking.

It sounds as tho you bought an old bike and expect it to act like it's new. As you've found out, it needs some TLC.

Did you download a factory service manual?

Not trying to sound like a grumpy old man (which I am), but we need more info on what maintenance you've done with the bike and whether the intake/exhaust is stock.

The cause of your problem is more likely an air leak or carbs out if sync than the linkage.

 

[850 Combat]

Synching the carbs without adjusting the valves first is pointless. Last time my valves were adjusted, the bike went back to perfect synchronization.

A stuck advance mechanism can cause a super high idle. I've never heard of that on a Suzuki. It is common on Commandos. What happens if you quickly flick the kill switch off and back on? That would unstick my Norton advancers.

 

[Mickeymoe]

I bought the bike from the original owner last season, it has 17k on it and I paid top dollar. Replaced the tires immediately and have been riding it with this issue while I converted it to a full dress Vetter setup. I kinda knew it had this problem when I bought it- when I'd move the handlebars the idle would increase and so I thought it was a simple thing like the throttle cable. I'm inclined to think it's a vacuum leak from a hose or somewhere else. BTW, my old GS850G that I sold had 26k miles on it (bought it with 7k) and never had ANY of these problems. So BigT, not to sound adversarial, but it's not a piece-o-s*** that I paid 500 bucks for and expect a new bike. The paint, chrome, and rubber is all near perfect. (I know inside the carbs, etc. doesn't count) just to give an idea of the condition. No rust ANYWHERE, and I mean ANYWHERE. Even the exhaust looks new.

Sure, the linkage snaps back, but why then if I press down on it would the idle decrease back to normal. How could that be an air leak?


Mark

 

[cowboyup3371]

Please follow the recommendations and go through the maintenance carefully