Bizarro problem

[Jim R]

1982 GS1100G. 100% stock.
#2 cylinder not firing. Have good spark.
Took gas tank off.
Hooked up external gas reservoir and plugged vacuum line.
Started and runs perfectly.
Took the time to adjust air / fuel mixture and sync carbs while the tank was off.
Runs like new with external gas reservoir.
Put gas tank back on. Made sure everything connected correctly.
Start up. Cylinder #2 isn't firing again.
Tried running it on reserve as well as prime. #2 doesn't fire.

Anyone??

[jsandidge]

Sounds like your petcock is dumping fuel through the vacuum line into the #2 carb making it too rich.

[Dragon Breath]

Check the routing of the plug wire to #2. Might be shorting on the bottom of the tank.

[Jim R]

Is there a fix for that?

[Jim R]

Spark is 100%

[Jim R]

Actually... I did remove the vacuum line while it was running to make sure there was vacuum. (There was) No fuel was coming out of the petcock.

[mrbill5491]

Okay need some of the long time members to chime in on Jim R. I've been chatting with him on Facebook and not come to a solution to his problem yet.

[tatu]

Has he checked for spark on the bad cylinder with the tank in place?

[Jim R]

Yes. Spark is good.

[loud et]

Test thw petcock.
Put the petcock in the run position. Add a small piece of tubing to the petcock vacuum port and give a little suck on it. If gas starts flowing in a nice stream and then stops when you stop sucking on the tube then your petcock should be fine. If the gas just dribbles out or does not come out at all then you have a seriously blocked petcock.
Simple test to see if you are getting fuel. Doesn't sound like it.

[loud et]

That or despite your efforts cleaning the carbs, there is some blockage somewhere in the #2 carb.
Just a couple things that came to my mind.

[hillsy]

Have you replaced the vacuum hose? It might have a split in it?

Or maybe a split / leak in the vacuum tap diaphragm?

It sounds like #2 is sucking air through the vacuum inlet rather than through the carbs and it can only be from the above.

[Jim R]

There's lot's of vacuum through the vacuum line. I'm hoping it's just a clogged up petcock. Emptied the tank. Going to take the petcock off tomorrow.

[Jim R]

Nah. Remember... It runs perfectly on auxilliary tank connected to fuel line.

[bonanzadave]

Nah. Remember... It runs perfectly on auxilliary tank connected to fuel line.

Where did you get the fuel in the aux tank ? Maybe you just have bad gas in the bikes tank.