HELP: Only Getting One Cylinder Firing

[95GSGUY]

So I went for about a 2 hour long ride a few weeks ago. Since I am from BC, Canada, the wet and cold weather started to set in, so I didn't ride it for over 2 weeks. I went to ride it just recently, and noticed I could barely keep it going without revving the throttle.

So I tried pulling the ignition wire off the left plug and it made no difference. I tried the same thing on the right side and it died instantly. So I concluded from this that I was only getting ignition in one cylinder.

Next I pulled the plug out of the left cylinder that wasn't firing and noticed it was sparking, but covered in oil. I replaced both spark plugs and tried the engine again. Once again, both got good spark, but the left side was still not firing.

I decided to drain the carbs and get some fresh gas in there. When draining the left side, I only got about a teaspoon of gas out, compared to the right side, where I got about 1/4 cup of gas out.

I had noticed while riding it all season that I got some hesitation when accelerating quickly, and especially when revving it for the first time each time I started it.

Does anybody have any ideas what I could/should do to fix it. Or has anyone experienced this same problem before??? Any help would be great

[JeffD]

Start the engine and spray some carb cleaner in the left carb....if it revs up its time to clean your carbs.

[gsJack]

A carb problem is possible but a loose spark plug wire in the coil is more likely it.  Pull the plug cap off and see if you can turn the wire around a turn or two clockwise.  If so that's probably the problem, tighten it as much as you can and try starting it.

If that's the problem you can cut a half inch off the coil end of the wire so it will tighten better and put a big gob of dielectric grease on the end of the wire before screwing it into the coil.  Should be good for another year.

The plug wires screw onto a post inside the boss on the front of the coil and they are bonded in there and can't be turned when new.  Coil and wire are sold together but once loose you can replace the wire by screwing a new one into the coil.

I had/have the same problem on the same left coil on my 02 GS and just replaced the wire for a second time.  Have over 65k miles on bike now.

[95GSGUY]

gsJack:

I'm not great with bikes mechanically yet, so I'm not quite sure I understand:

So even though I could see the sparks jumping across the spark plug to my left cylinder, it could be that the spark plug wire is loose?

Does that explain at all why I only had a very little amount of gas in the left carb float?

[95GSGUY]

JeffD:

Probably a dumb question, but when you say to spray some carb cleaner in the left carb, where exactly do I spray it? How do I get at it?

[JeffD]

To be able to do what I'm saying you'll have to pull the tank and airbox.  The engine will idle on the fuel in the floats for a minute or two. 

[gsJack]

First, it's quite possible to show good spark when checking with the plug out of cylinder and held against the head to ground and for it to then missfire when in the cylinder under compression pressure.  The spark will take the path of least resistance and with a little moisture added to the coil and frame and the greater resistance of the loose wire it can missfire.

Mine acted just like you describe and so did a couple of others here that had a loose coil wire.  In another recent case with the same symptoms it turned out to be a carb problem instead.  I could check for the loose wire in less time than it takes to type this and far less time than it takes to pull the tank and the airbox.  Just pull off the sparkplug wire cap and see if it will turn taking nothing apart.  If that isn't it you can persue the carb problem possibility.  I just changed my left side plug wire without even pulling the tank. 

[Paulcet]

gsJack may be referring to my recent case.  To me, it is certainly easier to rule-out electrical problems, but that may be just because my formal training is in electronics.  Follow gsJack's suggestion first and go from there.  Buddha might think carb problems are easier to diagnose and in my case, he was right.

Reminds me of a joke about 3 engineers riding in a car...