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running rough - part 2

  • Thread starter Thread starter maro
  • Start date Start date
M

maro

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Bike began running rough a few days ago. Part 1 ended with me checking all plugs, checking for leaks, etc. and thinking it's an exhaust issue. It's NOT.

Today I noticed a symptom I've felt before, a bit of stuttering from idle to 3rd gear. Could this be a Low idle circuit issue, AGAIN!! BUT, what's weird is, all my pipes ARE getting Hot, and the stuttering is happening intermittenly. The last time this happened (3 weeks ago), the 4th pipe was not getting hot, so it was easy to diagnose which carb to pull apart. Last time, it turned out the circuit jet plug crumbled and clogged the jet. I cleaned the jet and replaced plug with an extra I had...done!.

Let me mention that when diagnosing / pulling the spark plug caps , 3 & 4 showed little drop in idle movement...compared to 1 & 2 ( when I pulled 1 & 2 (seperately, the bike almost quit out).

Is there any chance that what is happenening is really due to a bad coil (the right one)? Is this another carb issue? If another cap fell apart, where can I get one, or do you know of a ghetto fix for a cap? help!
 
maro said:
Bike began running rough a few days ago. Part 1 ended with me checking all plugs, checking for leaks, etc. and thinking it's an exhaust issue. It's NOT.

Today I noticed a symptom I've felt before, a bit of stuttering from idle to 3rd gear. Could this be a Low idle circuit issue, AGAIN!! BUT, what's weird is, all my pipes ARE getting Hot, and the stuttering is happening intermittenly. The last time this happened (3 weeks ago), the 4th pipe was not getting hot, so it was easy to diagnose which carb to pull apart. Last time, it turned out the circuit jet plug crumbled and clogged the jet. I cleaned the jet and replaced plug with an extra I had...done!.

Let me mention that when diagnosing / pulling the spark plug caps , 3 & 4 showed little drop in idle movement...compared to 1 & 2 ( when I pulled 1 & 2 (seperately, the bike almost quit out).

Is there any chance that what is happenening is really due to a bad coil (the right one)? Is this another carb issue? If another cap fell apart, where can I get one, or do you know of a ghetto fix for a cap? help!
Click to expand...

It sounds to me as if you're running lean. A weak spark (if it makes it through the spark plug) will still fire the cylinder...and a lean cylinder (if not too lean) will still fire on a good spark. My gut is telling me that you're lean on 3 and 4 as they are fired from two different coils.
 
Dave8338 said:
It sounds to me as if you're running lean. A weak spark (if it makes it through the spark plug) will still fire the cylinder...and a lean cylinder (if not too lean) will still fire on a good spark. My gut is telling me that you're lean on 3 and 4 as they are fired from two different coils.
Click to expand...

thanks Dave,


Well, when I began yesterday, I checked the plugs. #4 was tan and #3 was blackened. So I replaced #3 with a new plug, and ran it a few mile and checked it again. It was tanning pretty quick. So I leaned out the mixture screw a quarter turn on #3.
 
maro said:
thanks Dave,


Well, when I began yesterday, I checked the plugs. #4 was tan and #3 was blackened. So I replaced #3 with a new plug, and ran it a few mile and checked it again. It was tanning pretty quick. So I leaned out the mixture screw a quarter turn on #3.
Click to expand...

Where were they set at, to begin with? A quarter of a turn (if they were set right to begin with) may have put you over the edge of the "lean cliff".
 
Dave8338 said:
Where were they set at, to begin with? A quarter of a turn (if they were set right to begin with) may have put you over the edge of the "lean cliff".
Click to expand...

actually, what I meant to say was it leaned the screw "IN" not "out", turning them in leans my carbs... and if they were turned too much in to lean them, could that then create that stumble?

I realize I should be doing the mixture screws at highest idle, etc... but the roughness came after the mixture screw had been set and the bike had been running smooth for a good while.
 
Last edited:
maro said:
actually, what I meant to say was it leaned the screw "IN" not "out", turning them in leans my carbs... and if they were turned too much in to lean them, could that then create that stumble?

I realize I should be doing the mixture screws at highest idle, etc... but the roughness came after the mixture screw had been set and the bike had been running smooth for a good while.
Click to expand...

OK...it has been a few years since I went through my carbs (same as yours) but if I remember correctly, on the CV carbs...in on the idle air screw (the one on top and at the front of the carb where it meets the intake boot), richens the mixture.
If I'm wrong on this, someone stop me now...
 
Dave8338 said:
OK...it has been a few years since I went through my carbs (same as yours) but if I remember correctly, on the CV carbs...in on the idle air screw (the one on top and at the front of the carb where it meets the intake boot), richens the mixture.
If I'm wrong on this, someone stop me now...
Click to expand...

STOP!
On CV carbs tight is lean, loose is rich.
 
SO I just ran out for a quick ride. She is definitely stumbling. Could my leaning out the one (#3) mixture screw make it stumble. As the bike got hotter, she ran a bit smoother.
 
maro said:
SO I just ran out for a quick ride. She is definitely stumbling. Could my leaning out the one (#3) mixture screw make it stumble. As the bike got hotter, she ran a bit smoother.
Click to expand...

Thanks, Doc! (age is catching up with me) And Maro...YES, lean runs better hot that cold.
 
Dave8338 said:
Thanks, Doc! (age is catching up with me) And Maro...YES, lean runs better hot that cold.
Click to expand...

Yep, knew I was a little too lean on pilot circuit because my idle would go from 1100 to 2000 when the bike got good and warm. You're just lucky you haven't had to screw with yours in a while.
 
Running lean...?

Running lean...?

I have an '82 GS850G. Lovely machine...of course.

A few years ago, I removed the airbox (can't remember why).

As it turned out, I knocked the rubber "snorkle" loose from the back of the airbox whilst reinstalling it. That caused a very lean condition that made the poor thing run like trash.

After discovering my mistake, I re-fitted the "snorkle" properly and went the trouble to apply weather stripping on the inside of the airbox to make sure there was no light visible (and no air leakage). This solved the problem. Read a post back then that said these bikes were set very lean at the factory to deal with (then) new EPA standards.

If you have been playing with the airscrews, I offer the following advice having fiddled blindly with them to bad effect myself.

I watched a pro fix my dabbling as follows: he closed all 4 airscrews (counterclockwise, I believe, but check that). He then advanced the idle screw at the back of carburetor so the bike would run. He then began opening each airscrew until the engine reached maximum rpms. After each airscrew adjustment, he turned the idle screw down/back to 1050 rpms, progressively setting each airscrew the same way. Thus, there is not a set number of turns for each airscrew, but "where each wants to be" as per the sage. Bike has run like a champ since.

You might have someone with the right equipment do a carb balance as it adds to smoothness, especially on closed throttle deceleration.
 
okay, so now it is day three and symptoms remain the same. I'm going to pull the carbs off and dive into number four. That pipe is not getting as HOT...AGAIN. Yey 27 year old bikes.... Why am I looking for a another, bigger GS?
 
maro said:
okay, so now it is day three and symptoms remain the same. I'm going to pull the carbs off and dive into number four. That pipe is not getting as HOT...AGAIN. Yey 27 year old bikes.... Why am I looking for a another, bigger GS?
Click to expand...

You'll get it, it's really not that tough. Follow the manuals or threads...these bikes are a lean burn beast. (that can be changed)
 
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