Dropping a cylinder HELP!

[Dad2g5]

How you guys doing? My 79 XS1100 standard is dropping a cylinder after cruising on the highway at 60 to 70mph for 10 minutes or so. After Stopping and letting it idle for a few minutes maybe 5, then is starts to fire again. its dropping cylinder #2. I cant figure it out. Cleaned the carbs for the 5th time now. They are spotless. Please Help!

[webbcraft2150]

First thing you have to do is figure out if you are losing spark or that cylinder is running out of fuel. Take a extra plug with you, when it croaks, pull the wire off, attach to spare plug and crank it, no spark, electrical, got spark, fuel delivery issue. You could also just pull the #2 plug and look at it, if it was starved for fuel, the tip should be dry and looking kinda white, indicates a leak condition. Or... swap plugs with another cylinder and see if it fires. I had a problem with NGK plugs that would just quit fireing, switched over to AC's and problem has gone away.

[skids]

Try opening the gas cap and see if she is vacuum locking. Check for kinked fuel lines. Make sure that inline filters are not clogged. Rust can clog the petcock filter towers (hope not). The pick-up coils can cause that also.

[Ken Talbot]

You are probably losing two cylinders. Go straight to the pick-up coil wire repair article.

[fredintoon]

just #2 or #3 as well?

Hi Dad,
there's a simple test to see if a particular cylinder is running or not and I learned it as a child from my mum. (well, she was checking if her iron was hot enough to do dad's collars, but still - - - )
With the bike running, lick your finger and quickly dab it on the exhaust pipe and off again. Average reaction time is 1/5th of a second. That quick. If that cylinder is running the spit should flash to steam under your finger. If it don't then it ain't.
I'd say if #2 & #3 are both dead, most likely Ken has nailed the problem.
If #2 alone don't work you have a weirdness. I confess to fighting with my own iggy for a week to get #4 to fire only to find that cleaning #4 carb did the trick.
Perhaps it's that 6 is your lucky number for carb cleaning?
Fred Hill, S'toon.

[HobbyMan]

If one cyl is cutting out, I would suspect old spark wires arcing before the plug

[randy]

Dad2g5;

To verify if it is a spark problem swap #2 and #3 plug wires. If the problem moves to #3, then you have a spark problem. To try and cure it, remove the plug caps (unscrew from wire) and clip 1/4" off, that will expose fresh wire, re-install caps.

If you move the wires and the problem stays in #2, then you have a carb (sorry) or valve (yikes!) problem.

[HobbyMan]

Do a compression check when its hot