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GS550L Cold #2 Cylinder

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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My 1981 GS550L is giving me a real troubleshooting challenge, and since I've had no luck for two months, I thought I'd see if anyone's experience might lead to some new suggestions.

The problem is that the number two exhaust pipe is staying cold almost all of the time, and lately all the time. My first thought was no spark, so I checked it and it seemed weak. I replaced the boot cap, and coil for number 2 & 3, strong spark on number 2 now. Still less power, cold #2 pipe. The same syptoms, and a lot of fuel coming out of the left exhaust pipe (whitish smoke if ridden). I checked the float height settings on all carbs, and adjusted them to within spec (only one was slightly out, but not No.2). The needle valve is functioning, the float is not sticking, and I just don't know enough about the carbs to guess what the next item to check is.

I've also replaced the no. 2 spark plug several times throughout this process.

I would love any suggestions, because I'm missing some of the best riding weather and scenery! Thanks

-Matt, 1982 GS550L
 
Additional info I forgot to post:

Miles on Engine : 18,000
Most Recent Work Done: Cam Cover Gasket Replaced, Starter Rebuilt, new rubber tubes between all 4 carbs and air box replaced, Ignitor Unit Replaced, Turn Signal Replaced, New Chain,

- Cycle was running excellent until late August, then there was occasional bogging down, (i.e. running on 3 cylinders), but would be very intermittent with no relatoin to hot or cold, running long or just started, etc.

Hope this helps some

-Matt
 
you best bet is to clean every bit of the carbs, it sounds like you have some dirt somewhere inside them. and when i say clean i mean strip apart, replace the o rings, and dip the carbs. i wouldn't bother with rebuild kits just get the o rings. my bike was doing similar things and come to find out that there was a pile of dirt in the filter screen over the float needles.

ryan
 
You need four things for a cylinder to fire: fuel, air, compression, and spark. You checked spark, but did you check the others? You might want to have a deeper look before you take the carbs apart. That may still be what it comes to, though.

Michael
 
Shirkzuki said:
Additional info I forgot to post:

Miles on Engine : 18,000
Most Recent Work Done: Cam Cover Gasket Replaced, Starter Rebuilt, new rubber tubes between all 4 carbs and air box replaced, Ignitor Unit Replaced, Turn Signal Replaced, New Chain,

- Cycle was running excellent until late August, then there was occasional bogging down, (i.e. running on 3 cylinders), but would be very intermittent with no relatoin to hot or cold, running long or just started, etc.

Hope this helps some

-Matt
Click to expand...
I didnt read the whole thread but did you say which cylinder was fouling when it was running on 3??
 
-I haven't checked compression on the number two cylinder yet. I have made sure that air can get to the carb freely, and through the carb to the manifold and the fuel is getting there, alas it seems to be too much fuel. I'm becoming an old pro at getting the carbs in and out, so I'll probably strip them down completely, replace the O rings, and if nothing else, I'll learn something about the carbs this weekend!

Thanks for the replies, and I will mention how the complete carb check up goes.

-Matt
 
You said the left side exhaust was blowing white smoke. This is oil burning, not a rich mixture. Is the sparkplug black and kind of shiny/sticky? Could be rings or valve seals. I think the plug is oil fouling. Check the compression.
 
might need to lean the mixture screw out on the front of the carb...by turning the screw...OUT, right?

its backwards on CV carbs.
 
another thing to check for is a burnt valve and this will come to light in a comperssion test cause you won't have any 8O. from what i have read you have spark you have fuel and you have air so that leaves only 1 thing suspect "compression", and another point that leads me in this direction is that you said it started out very intermitent and steadly got worse until it is now not firing on it at all, this leads me to think that it is a compression problem IE: RINGS OR A BURNT VALVE and best hope for rings cause it is easier to deal with than a valve if it's a valve then off to the machine shop you go unless you have the know how to (and a valve spring comressor ) to fix it, also you will need a new valve seat and a grind (machine shop only) and if your going to do 1 then do them all cause if you don't then your just going to be doing it again soon :cry: another way around this is to look for a good used head and just swap it out for your bad 1 if it is bad but be sure to have it cheaked before you install it so you don't wind up in the same spot your in now
hope this helps you out some

Spyder Out
 
AOD said:
might need to lean the mixture screw out on the front of the carb...by turning the screw...OUT, right?

its backwards on CV carbs.
Click to expand...
Hi Adam. I looked at a drawing of a typical CV carb pilot circuit. If you turn the pilot screw out, it opens a second passage more. This would increase the amount of mixture, so you would be richening it.
Where did you hear that CV's are backwards?
 
What does the number 2 spark plug look like when you remove it.? especially compared to the other three.

Check the easy stuff first! I think #2 has the vacuum line that goes to the fuel petcock. Pull the vacuum line of the petcock and make sure it has no fuel in it. (leaking diaphragm in the petcock) The vacuum line could also be sucking air.
 
Keith, what you says makes sense...someone else confused me prior to this post about CV carbs...so that's why i said that.

Shirtsuki, try leaning the mixture to that cylinder...
 
Thanks for all the suggestions: I'll try to answer some of the quesitions, all the suggestions are great!

I checked compression across all four cylinders on a cold engine:

-Each cylinder read 120 PSI Cold, good news for me

Only one spark Plug is fouled:

-Number 2 Spark Plug gets wet with gasoline only I beleive, wipes off very easily

The fuel petcock seems to be functioning normally

-No fuel in the vacuum line, vaccum exists, plugging the line with no leaks gives no change

I will try to adjust the pilot screw on the front of the number two cylinder carburetor, and I'll post the results. Thanks for everyone's input
 
problem solved

problem solved

The mixture adjustment fixed the problem for now, I may have to fine tune the mixture on that cylinder, however I just made it lean enough that it runs well (no more smoke). I also have to change the oil now, some gas got into it while it was being dumped into #2 cylinder.

Thanks for all the feedback, it helped out a lot!

-Matt Shirk
 
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