GS 850 G help please.

[The Artful Bodger]

This is driving me mad!! When I have the choke out on my 1979 (VM carbs.) GS 850 it revs like mad. I took the choke plungers out, fitted an O ring between the screw in top and the spring adding some rubber grease between the rubber seal/cover and the new O ring. Started it up and happy days, problem solved, obviously it's sucking air past the rubber seal on top of the choke screw in top when the choke's on.
Over the next few days the revs on choke gradually got higher until I'm back to where I started. I did wonder with the O rings being on the vacuum side of the cap whether they would suck down enough against the spring pressure to allow air in. I think this is what's happening and only the grease was giving me a seal.
Simple solution, replace the rubber seals, HA! I can't find a parts diagram which even shows any of the choke parts, the main dealers over here (UK) seem to have the same diagram as they can't find them. Despite hours internet searching it would appear that someone cleverer than I is needed to track them down over here.
You guys in the US of A seem to have a much easier time with GS parts than we do over here. I would be forever grateful if someone could tell me where I could possibly buy them in the States.

Thanks

Colin

 

[Steve]

I guess we would have to figure out which is the "vacuum side" of the plunger. :-k

The plungers open a fuel passage and an air passage, there is no real "vacuum" involved. There should also be no need for much of a gasket (o-ring) around the shaft and the spring. There is a thin o-ring around the nut that holds the shaft in place, though.

Because of the way the "choke" works, the engine might "rev like mad" because the "choke" is providing its own air source. Try applying a bit less than FULL "choke" to bring the engine speed down. I like to keep revs on a cold engine below 2500, if possible.

It also sounds like you might benefit from a full refurb on the carbs. You can order all the o-rings necessary from a fellow member at cycleorings.com.

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[The Artful Bodger]

Thanks for the reply Steve, I replaced the O rings, float needles and seats a while ago and the carbs are working fine except on choke. Less choke gives me popping and banging back through the carbs and exhaust and it won't rev up by the throttle until the choke is off. All pointing to an air leak from the choke since fitting an extra O ring and packing grease between the new O ring and the rubber seal completely cured all the problems (over reving, popping with less choke on and instant response to the throttle with the choke on) for a few days until I assume the grease got sucked in.
40 years as a mechanic gives me some confidence in my reading of the problem, what I'm stuck on is where to buy the rubber choke seals for the VM carbs.

Thanks
Colin

 

[Steve]

Congratulations on the 40 years as a mechanic. :clap: :clap:

How many years on a GS? :-k

Not trying to be insulting, just that the "choke" works differently on these carbs, not anything like what is found on automobiles.

Our usual source for o-rings (all the ones that WE have found necessary) come from the source mentioned in my previous post, but here is a link so you don't have to scroll back and look for it. I even have it pointing at the page for VM carbs. Cycle o-rings.

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[The Artful Bodger]

Congratulations on the 40 years as a mechanic. :clap: :clap:

How many years on a GS? :-k

Not trying to be insulting, just that the "choke" works differently on these carbs, not anything like what is found on automobiles.

Our usual source for o-rings (all the ones that WE have found necessary) come from the source mentioned in my previous post, but here is a link so you don't have to scroll back and look for it. I even have it pointing at the page for VM carbs. Cycle o-rings.

.

Just as a by the by in case anyone else is having problems with excessive reving on choke, I am giving an update here. I managed to find the choke cap seal from a supplier here in the UK. Actually they're not listed as the ones for 1979 VM's but are for their new 29 mm carbs, however a very helpful guy took a vernier into their stores and we compared sizes (choke cap sizes!) over the phone.
Before replacing these choke caps I was getting 4000 RPM on full choke and it would stall as soon as I tried reducing the amount of choke. There was one choke position where it would keep running without over reving too badly but it coughed and banged back both through the carbs and from the exhaust. With the choke on in any position any try to twist the throttle to rev the bike would stall it instantly. Cold starting was a case of full choke then trying to find this "one choke position", which usually took several attempts, and just leaving it popping and banging for a few minutes until I could kill the choke and tickle the throttle to get it to rev. Once reved once it would be fine from then on. Even despite NOT being a top notch Suzuki mechanic I did manage to figure out an air leak was the problem, and since it was only on choke it kind of gave me an clue where to look.
Fitted the new choke cap seals and full choke now gives me 1800 RPM. I can rev up on the throttle from any choke position so despite the "advice" given above I figure the problem's solved? If anyone in the UK is looking for these seals, or other carb parts, try Allens Performance LTD. they were very helpful to me.

Colin