1980 gs1000g

[ironbiker]

Carbs rebuilt by Wired George around 9 months ago,new intake boots,ignition rewired to get full 12 volts to coils. Starts fine,idles fine ,warms up and starts revving to 2-3000rpm,will not idle until cold again,driving me effing nuts.I bought this bike new,did the alternator update,new clutch,front and rear master cylinders replaced,new petcock and fuel lines,new coils and wires,new mirrors,I guess I should have bought another bike...baffled in Orlando.

 

[tom203]

You bought this bike new….?
anyways, did you use new o-rings under the new carb boots? Sure sounds like air leak as cylinder head gets warm.
did you sync throttle positions?

 

[ironbiker]

New O rings were installed,carbs were bench synced by the one of the best carburetor men in the country. I've had same problem with old carbs and old boots,all this work and no change.I've read that maybe a valve adjustment would cure this..I dunno.

 

[Nessism]

You have an air leak.

 

[ironbiker]

Suggestions.....?

 

[unfocused]

Are you running CV carbs?

I'd guess something is out of sync or an air leak as already mentioned.

A stuck ignition advancer could also cause a smiliar issue.

Don't blame the bike. It did nothing wrong.

I've had plenty of issues with my GS750 and GS1000 but was always able to solve them.

 

[Rich82GS750TZ]

I'll ask again. You bought this bike new? in 1980?

If you haven't done valve clearance check, or had it done recently by one of the best valve clearance check men in the country, then I'd get to it. It certainly can't hurt, and probably really needs to be done.

 

[Nessism]

I've seen two different sets of "George's" carbs, where the carbs were heavily contaminated by blasting beads on the inside. I had to do a full teardown to clean them out properly.

These are the O-rings that commonly leak air.

 

[salty_monk]

carbs were bench synced by the one of the best carburetor men in the country.

That is highly debatable... Lots of mixed reviews of his work if you search around. Personally I would tear them down myself over anything from that particular source. Check for leaks everywhere. Carb boot o-rings. Carb boots to carbs. Carb mouths to Air box. Air Box itself. Vacuum lines. Good luck!

 

[Nessism]

I've read that maybe a valve adjustment would cure this..I dunno.

I hope you realize that valve adjustment isn't an optional thing. Failing to adjust the valves will damage the engine.

But, no, valve adjust will not cause a creeping idle.

 

[ironbiker]

With the all the work I've done to it with no different results I suspect a crack internally...BTW the valve adjustment procedure on these engines is a clusterfxxk ,IMO. The valve adjustment will be done when and if I solve the creeping idle problem.I'm sure I'm not the only one to have this specific malfunction.

 

[rphillips]

Where are you anticipating a crack, I've not seen that before... Adjusting valves may be a little aggravating, but hardest thing about checking them is removing valve cover.

 

[Nessism]

The valves on the shim and bucket GS's are very stable. It's one of the reasons these bikes run to 100,000 miles easily. They are dead easy to check too, and don't often need adjustment. I agree with rphillips that the most difficult part is removing the valve cover.

A creeping/hanging idle when hot is almost always related to the intake system in some way. A vacuum carb sync is required, and you can also try opening the pilot screws a little more. If the airbox side cover foam seals, and/or the seal on the air filter cage, is deteriorated, that will allow false air to enter the system also.

 

[Rich82GS750TZ]

You think shim over bucket is hard? Try a Triumph Triple or other engine w/ the shims UNDER the bucket.:dejection:

 

[rphillips]

Yes, try my Honda CB1100F, shims under buckets, 2 cam chains, 2 cam chain adjusters. Royal PITA...Hard to imagine Suzuki started using "under the Bucket" in their 2007 Bandit 1250's.... For me as rare as spitting a shim is, they tried to fix something that wasn't broke, and just caused more problems... Also don't try to make me believe they did it to save wgt. on the valve train... That's what Kawasaki said back in the early 80's when they did it.

 

[Nessism]

Yes, try my Honda CB1100F, shims under buckets, 2 cam chains, 2 cam chain adjusters. Royal PITA...Hard to imagine Suzuki started using "under the Bucket" in their 2007 Bandit 1250's.... For me as rare as spitting a shim is, they tried to fix something that wasn't broke, and just caused more problems... Also don't try to make me believe they did it to save wgt. on the valve train... That's what Kawasaki said back in the early 80's when they did it.

KZ650, which came out in 1976, is shim under bucket. It's more stable and lighter. Racers guys put the 650 buckets into their big KZ's for that reason.

 

[rphillips]

Wondering if there were ever an estimation of how often the shim over bucket would spit a shim, I'd say never without excessive over revving. But however rare it was, the under bucket took care of it, just added 3 or 4 times longer to adjust the valves at every valve adjustment...

 

[ironbiker]

Airbox removed,carbs rejetted..running pods..same creeping idle after all this changed,still looking.

 

[Nessism]

How many turns open are the pilot screws, and did you perform a vacuum sync?

 

[KiwiAlfa156]

Wondering if there were ever an estimation of how often the shim over bucket would spit a shim, I'd say never without excessive over revving. But however rare it was, the under bucket took care of it, just added 3 or 4 times longer to adjust the valves at every valve adjustment...

Well, you'd think to flick a shim it would have to be in serious valve float/bent valve territory


In his book Croz: Larrikin Biker, Graeme Crosby wrote about the 8-valve GS superbikes he raced (including the XR69) were sensitive to rpm limits, and lunched their valve-trains if they over-revved (no rev limiters back then). A missed gear was blown engine and a guaranteed DNF. And these were proabley fitted with shim under buckets.
https://www.classicmechanics.com/book-review-graeme-crosby/
https://www.motorcycle.com/features/archive-suzuki-xr69.html