GS550L Cylinder not firing, has compression, spark, and fuel. Gas leak from exhaust.

[jscislaw]

Hey friends,

I might have a bald spot after scratching my head so hard on this one.

Bike: GS550l 1981 Suzuki

After cleaning the carbs three times, I can verify that all cylinders are getting fuel. New plugs are all getting electricity, and all cylinders are showing healthy levels of compression. However, for some reason cylinder #2 is giving me trouble, either firing very infrequently, or not at all. The #2 exhaust port is cold to the touch after running, while the others would burn flesh. After testing it three times, the #2 plug was wet once, and dry twice, leading me to believe its firing occasionally.

Now here's something I have never seen before. The exhaust connection port on the bottom of the bike is leaking a significant amount of fuel. Once guess is that it's coming from cylinder #2, which may be getting too much fuel. Even if the cylinder wasn't firing occasionally, there was so much gas leaking from the exhaust that it just doesn't seem right.

Is something plugged in carb #2 that's letting too much gas into the cylinder? Could the exhaust leak be coming from somewhere else?

I would appreciate any suggestions!

 

[gustovh]

You told us that you cleaned the carbs, did you dip them or just spray carb cleaner? What adjustments have you made to the carbs> Pilots out 2 turns as a starting point, bench sync? 1/8" drill works well and will get you close.

You might have a couple issues. Your gas valve might be leaking, if it has a hole in the diaphragm or the O ring seal in the gas valve is leaking, the gas would run down the vacuum tube into #2 cylinder.

The next thing to try is unscrew the plug cap on #2 wire and cut about 1/4" off of the wire and screw the cap back on. A little bit of spit on the outside of the wire helps lubricate when screwing the cap on.

If that doesn't work check for a vaccum leak on the #2 intake boot at the head.

Be sure to check your oil for the smell of gas, if it is overfull change it and you have a leaky gas valve.

 

[Almonus]

I was having the same problem with my gs 750T. It worked fine with an auxiliary tank but the stock gas tank was flooding out cylinder 2. Turned out to be a leaky gas valve, annnndddd now it's back to fine tuning the jetting.

 

[tkent02]

#2 has the vacuum line to the petcock, if your petcock diaphragm leaks you can get way too much fuel in that one. I have seen it leak so much fuel it can't fire very well. Try running the petcock on Prime, blocking of the vacuum port on the carb and see if it hits on all three. Or just suck on the vacuum line and see if any fuel comes through, with a good petcock there won't be any.

Do not leave it on Prime when the engine is shut off.