83' GS850GL idle problem after carb rebuild

[nanoluxx]

To get you up to speed. I bought this (83’ GS850GL) bike not running. I just finished rebuilding my carbs and sealing my gas tank. It now cranks and gets running with full choke and a bit of starter fluid. It starts up at about 5,000 rpms. I then lower the choke all the way. The RPM’s drop to about 3,000. I wait for a few moments without any throttle and it eventually (rpm’s dropping slowly) stalls. Throughout the whole process there is a lot of backfiring. I have the air mixture screws 2 turns out from seated. When I started the process it wouldn’t idle at all and I slowly turned the idle screw in until it would stay on. I also noted in one attempt when I started to see it stall again, without any choke, I tried to throttle it a bit and it still stalled.

Any idea’s?

Thanks,
Jayson-

[Dave8338]

Where is the base idle set screw at? Have you backed it out all the way?
Airbox sealed tightly with filter in and lightly oiled?

[bwringer]

First off, throw that starter fluid into the garbage can. That crap is dangerous to you and your engine and has absolutely no use anywhere near your bike.

Secondly, the airbox and air filter MUST be mounted and properly sealed to get an 850 to run right.I suspect that's your problem.

Also, set the idle mixture screws to 3 turns out and make VERY sure your float height is set EXACTLY at the lowest measurement given in the manual.

Oh, and the valve clearances are adjusted correctly, right?

[nanoluxx]

The air box is sealed and oiled. The base idle set screw.. is this is the long screw attached to the master carb, which when screwed in restricts how far the throttle can rest back or idle? I called this my idle screw in my first statement. If so.. no, it is not backed out. Should it not be restricting the throttle at all?

On a more recent trial the bike stayed idle much longer and at a more realistic RPM but when I tried to throttle, it stalled. Does this hint to anything else I should check?

[nanoluxx]

First off, throw that starter fluid into the garbage can. That crap is dangerous to you and your engine and has absolutely no use anywhere near your bike.

Secondly, the airbox and air filter MUST be mounted and properly sealed to get an 850 to run right.I suspect that's your problem.

Also, set the idle mixture screws to 3 turns out and make VERY sure your float height is set EXACTLY at the lowest measurement given in the manual.

Oh, and the valve clearances are adjusted correctly, right?

Okay.. no more starter fluid. thanks for the tip

I thought to have sealed the air box well, but I'll check it again.

and I'll try to turn those mixture screws in one more time.

[lucabond]

It sounds like its getting to much fuel. Did you replace the fuel inlet o-rings when you rebuilt the carbs ? Good luck

[bwringer]

If the airbox is on and all that and it will only run on choke, then the idle passages and/or pilot jets inside the carbs are still completely clogged.

The carb cleanup series points out everything in detail, so please review that information.

[nanoluxx]

If the airbox is on and all that and it will only run on choke, then the idle passages and/or pilot jets inside the carbs are still completely clogged.

The carb cleanup series points out everything in detail, so please review that information.

I cleaned my carbs using the carb cleanup series. I dipped all parts in berry-mans chem dip.. and could see through all the passageways when I was done. It should be clean. I also have all new jets.

It sounds like its getting to much fuel. Did you replace the fuel inlet o-rings when you rebuilt the carbs ? Good luck

Yes, all O-rings were replaced. Is there something I can tune to reduce how much fuel its getting?

[Dave8338]

I cleaned my carbs using the carb cleanup series. I dipped all parts in berry-mans chem dip.. and could see through all the passageways when I was done. It should be clean. I also have all new jets.
?

There are several passages that can't be "seen through". It is best to follow the chem dip with a few cans of carb cleaner spray using the little red tube as even it...is too large for most of the passages. After all of this I use the air compressor and blast everything I can find.

[nanoluxx]

I used both spray carb cleaner and compressed air after the chem-dip.

[rustybronco]

Where are your fuel "levels" at? (not the measured float heights). they should be 5mm below the carb body IIRC.

what do the spark plugs look like?

[Dave8338]

Then it has to be in the set up and or it may be the o-rings between the intake rubbers and the head. Somewhere you're leaning out which is what causes the base idle to climb and then drop off. If everything in the carbs is clean and you're sure that they're set correctly it must be too much air. That or you petcock is not flowing correctly. One way or another the air fuel ratio is lean...

[nanoluxx]

Where are your fuel "levels" at? (not the measured float heights). they should be 5mm below the carb body IIRC.

what do the spark plugs look like?

How do I check my "fuel level"? and the spark plugs are new... and seem to be firing fine.

Then it has to be in the set up and or it may be the o-rings between the intake rubbers and the head. Somewhere you're leaning out which is what causes the base idle to climb and then drop off. If everything in the carbs is clean and you're sure that they're set correctly it must be too much air. That or you petcock is not flowing correctly. One way or another the air fuel ratio is lean...

I replaced the intake boots and o-rings between the carb and head.


Recently while ive been tinkering with the air-screws.. 3 turns out from seated not working at all, or very poorly, 2.5 turns out working the best, 2 turns out over rev'in.. I've noticed a jet sound every once and a while. the moter will idle with no throttle (if i try to throttle at all it stalls) and the choke all the way open (if i reduce choke it stalls) and while its sitting there, running fairly normal RPM's I hear a psss sound, shorter and not nearly as loud as a turbo blow off valve coming from the front of the bike somewhere. When this sound happens the bike seems to want to stall but it recovers and keeps going normally. It eventually stalls...

[nanoluxx]

Recently while ive been tinkering with the air-screws.. 3 turns out from seated not working at all, or very poorly, 2.5 turns out working the best, 2 turns out over rev'in.. I've noticed a jet sound every once and a while. the moter will idle with no throttle (if i try to throttle at all it stalls) and the choke all the way open (if i reduce choke it stalls) and while its sitting there, running fairly normal RPM's I hear a psss sound, shorter and not nearly as loud as a turbo blow off valve coming from the front of the bike somewhere. When this sound happens the bike seems to want to stall but it recovers and keeps going normally. It eventually stalls...

Anyone have any theory of why this sound is happening? Is my engine depressurizing somehow? Is this signs of an air leak?

Before I rebuilt the carb, the bike would start up and I could keep it running for a good amount of time by keeping a little throttle on it. Now I can't throttle at all without stalling but it runs without throttle?

[Octain]

Anyone have any theory of why this sound is happening? Is my engine depressurizing somehow? Is this signs of an air leak?

Before I rebuilt the carb, the bike would start up and I could keep it running for a good amount of time by keeping a little throttle on it. Now I can't throttle at all without stalling but it runs without throttle?

Did you replace the air jets, the ones on the outer edge of the carb where the airbox connects? Whats brand of jets did you use?