GS1000 1979 or 1980 mostly 80 no points.

[mike10]

I have the BS34SS carbs I'm getting some backfire from time to time from # 4. I got it to idle between 1500 and 2000 for the carb syinc which seemed to go alright. When I blip the throttle the rpm's drop back down slowly. Then all by it's self while idleing the RPM's will start climbing up slowly to around 4000. Chokes not on. I feel like its trying to tell me something? Anyone know what it could be? I checked the throttle cable working nice and free.

[tkent02]

Most likely vacuum leaks.
What has been done to the carburetors and intake system?
What engine maintenance has been done?
Has the bike sat a long time?
Has it always run this way?

[Big T]

Classic lean condition

Intake boots?

O rings?

Clean the carbs per spec?

[mike10]

Capped Off

GS1000 1980 BS34SS carbs the only vacuum I found was on #2 that went to the tank capped her off. The engine was in pieces I took the head and pistons cylinders to a shop and had the guy there measure everything do the valves and new guides it's pretty much like a new old engine. The short answer is I don't know most of the stuff you asked. I cleaned the carbs per instructions from GS web site. All new gaskets and O- rings stock air cleaner with holes repaired. What do Ya think

[tkent02]

GS1000 1980 BS34SS carbs the only vacuum I found was on #2 that went to the tank capped her off. The engine was in pieces I took the head and pistons cylinders to a shop and had the guy there measure everything do the valves and new guides it's pretty much like a new old engine. The short answer is I don't know most of the stuff you asked. I cleaned the carbs per instructions from GS web site. All new gaskets and O- rings stock air cleaner with holes repaired. What do Ya think

Did you replace the o rings between the intake boots and the head?
What are you using for a petcock?

[mike10]

New O-rings

Yes, New O-rings between head and boots. Stock petcock, I took the O-ring off the little vacuum thing in the petcock so the gas would run straight through while I was working on the carbs. There's no leaver for off, on, RES. Have to use a screw driver it leaks a little gas where you turn it with the screw driver.

[blakebird]

I just went thru some of the same symptoms you're having, on a 1981 GS1000G I recently bought.
(btw, a vacuum petcock will flow gas on the "PRI" prime setting. You can leave the vacuum hooked up)

My GS had the top end rebuilt at 53,000 miles. New rings, honed cylinders, new valve guides/seals, relapped valves.
My idle would climb as the engine got to temperature, to about 2500-3000 rpms. Started easily with no choke from cold.

I took the airbox off and carbs too. I replaced the o-rings in the intake manifolds - but the ones I removed were quite good still, I think they'd been replaced before. I also replaced the float needle seat o-rings.
The ones I could not get to, were the 12 that are in the connector tubes.
The rack mount philips heads were so tight - I didn't want to bung them up, and there was no leaking going on there...that I decided against breaking something while trying to fix it.

The airbox's foam seal between the element and the airbox was bad at each end - once I replaced the foam seal the idle barely climbs at all anymore. Once warm, the idle stays nice and low, but will wander to 1500-1800 rpm's for a moment, then go back down...and not often at that.
I think it was a combo of that and the fuel/air screws being ~4.5 turns out when I bought the bike. They're at 3 turns out now, and I'm going to try 2.5 turns out. Throttle response is not bad at all. Not perfect, but certainly livable if 1/2 turn more does nothing.

[chef1366]

Did you set the float heigth?

[blakebird]

Did you set the float heigth?

I'm sure the question is directed at the o.p., but I checked mine while I was in there, they were all spot on. The insides of my carbs looked as new, diaphragms and all looked like new pieces.

[mike10]

Blakebird Yep

Thanks, my problem sounds the same as the one you had.RPM's climb when its warmed up. I,m going to check that stuff out.

[blakebird]

Thanks, my problem sounds the same as the one you had.RPM's climb when its warmed up. I,m going to check that stuff out.

My climbing idle is not completely gone.... I took the bike for about a 200 miler today, the first chance I've had to ride it longer than 'round the block since getting it back together.

When good and warm (stop and go traffic), it is still climing to 1500-1800, and on occasion around 2200 rpm. A little frustrating, but at least it's winter and I have a couple other bikes to ride while I dig deeper.