GS850 high idle, one more time....

[Guest]

Tonight, after I reinstalled the air filter with the new weather stripping, I left the choke completely off - AND the bike hadn't run in three days. It started instantly and raced immediately to 3000 RPM. Something is way off, and I really don't think it's anything to do with the installation. I have removed and reinstalled the carbs several times by now, and there's just not that much to it. So this weekend I'm going to pull them back off and bench sync them and see what happens.

And I'm also going to do another compression check; the #3 exhaust pipe is slow to warm up, the bike spits and sputters when it's running, and there is an intermittent metallic clanking sound coming from the vicinity of the clutch/right-front of the engine that has me worried.

 

[jlyon40]

I had a similar problem with my 81' 850g recently and with mine when it first started it would idle low and then when the bike warmed up it would jump to 2500-3000. I fixed mine by getting a new airfilter and also get some weatherstriping tape that I got on amazon for less than $10 to make sure the side covers and the top of the air filter were air tight. I also had to bring my idle adjustment screw down a little bit and now she's running fine, no problems after warming up or anything.

 

[Guest]

I had a similar problem with my 81' 850g recently and with mine when it first started it would idle low and then when the bike warmed up it would jump to 2500-3000. I fixed mine by getting a new airfilter and also get some weatherstriping tape that I got on amazon for less than $10 to make sure the side covers and the top of the air filter were air tight. I also had to bring my idle adjustment screw down a little bit and now she's running fine, no problems after warming up or anything.

Hi. Thanks for that input. I've done all of that on my bike. Nothing. So the next thing is to try spraying carb cleaner on all the air connections to see if I can spot a leak. And if that doesn't find it, there's nothing to do but pull the carbs back off and start inspecting them closely for issues.

 

[eil]

While I'm not as much of an expert as some gurus around here, I have managed to get my 850 running great. Like they say, you won't get very far only doing some of the maintenance. Since we both live in the same neck of the woods, I'd be willing to stop by and offer a hand. I have everything needed to dial in valve clearances (minus the gaskets and maybe some shims) and do a proper carb sync. PM me if interested.

 

[Guest]

Woo hoo!!!!! I found the problem! Apparently, all four of the throttle butterflies have to be perfectly flat. After a vintage bike mechanic in Austin, TX ("Chris" at Limey Bikes) told me that before you bench sync your carbs, you need to make sure all four are able to make a perfect seal around their perimeter - at the same time. When Charles (from Ypsilanti) was here a few weeks ago and we were inspecting the carbs, we noticed the the #3 had a few dings on the edge, so I filed those down gently and made the edge as smooth as I could, but I did not remove the valve from the carb so that I could inspect it closely. So a few nights ago I pulled the carbs - again - and did a really close inspection to see how well they valves were able to seal; #1, #2 and #4 were perfect, but the bottom of #3 showed a fair amount of light through it. So I removed the valve from the shaft so I could see it from the edge, and sure enough, it was a bit "potato ship-y" around the edge, and there was evidence of having been mistreated by a PO. Luckily I had another one on the way from Ebay and installed it tonight. Eureka! Charles has graciously loaned me his CarbTune Pro, and I've got the four cylinders close, but I suspect there's still room for improvement.

I'm convinced that this is a really unusual situation. I mean, how many people run across a warped butterfly valve? So along with all the great advice about checking for vacuum leaks, too-tight throttle and choke cables, etc, be sure to check your butterfly valves for flatness! Hope this helps someone.....