Dead Cylinder

[mbautsch]

I have a 81 gs550t. My number 2 cylinder is dead. When all of the other pipes are way too hot to touch I can grab and hold on to the number 2. I have 2 sets of carbs and I have tried both of the number 2 carbs and rebuilt them both. I have cleaned them extensively during the rebuilds, several times. I have good compression in the cylinder and I have a spark at the plug.

Any Ideas?

Thanks

[relic-rider]

Is the plug wet? Your petcock could be leaking gas down the vacuum line hooked to #2 flooding it out. A wet plug will sometimes spark outside the engine, but under compression will not. Change the plug anyway.

[mbautsch]

Thank you! The petcock is bad. I put a vacuum plug on the vacuum on number 2 and plugged the vacuum on the petcock and ran it on prime and it worked great. I guess I need to rebuild the petcock.

[Nightmare]

OMG... i wonder if this is the same problem on my 80' GS850... I'm having the EXACT same problem and I have tried everything under the sun to fix the problem (tomorrow I was going to run some Sea Foam through the tank to clean the intake valves that I suspect might be sticking?)

[Nightmare]

Interestingly enough, the petcock on my tank was bad. I hooked up a clear tube to the vacume line and could see it sucking a ton of fuel. I got lucky and found a brand new replacement for 30$ but my #2 cylinder is still cold (appears to be running really rich). Carbs are synced, floats adjusted, carbs cleaned (air passage ways, jets, etc). Good spark, good compression, the only thing left to check are the valves... When i pull the #2 plug its damp (wet, but not as bad as it was before the petcock was replaced)

[relic-rider]

Did you put a new plug in #2? Do that before checking anything else. Plugs foul out real easy when they get wet, then they stop sparking and just get worse.

[mbautsch]

Nightmare, change your oil!!!

Once I discovered that fuel was just dumping into the #2 cylinder I changed the oil and filter and it reeked of fuel.