The rear cylinder on my 2002 fxstb failed. I was riding and it quit. The engine was still running. I rode it home (about 1.5 miles) lijke that. When I got home, after it sat a few minutes, I started it again and it sounded normal for about 30 seconds then the back cylinder failed again. I decided, sinceI wanted to upgrade to 95", to take the top end off while exploring the problem. After pulling everthing off I didn't see anything that would have indicated a mechanical problem. There was plenty of gas in the crank case though. I have since had my cylibders bored, installed new SE pistons, installed a set of Crane 310 cams, and new gaskets all around. The only upgrades i had on the bike previously were a thunderheader, a DSO fue manager and a Ness Big Sucker. I have asked around quite a bit as to what might have been the original problem and have yet to here a definite answer. More often than not, folks have mentiond the coil. Any takers?
Thanks

 

It definately sounds like an ignition problem. Possibly just a loose/broken plug wire or fouled spark plug. Those things should have been checked first. You could also have a broken wire in the coil. I've had that happen. Once the coil gets hot the wires separate and you loose that cylinder. The last thing in the system to check [besides the wires that connect everything] is your ignition timing module. It sends the signal to the coil to fire each cylinder. If one of the electronic components has a loose solder connection it could cause an intermittent problem with the spark.

Doing the top end upgrade would not have changed any of those things unless you changed the plugs and wires. Your service manual will have the ohms check limits for the coil, but if it's an intermittent broken wire the ohms check could show it's good. Again, that happened to me.

Good luck!

 

It happened to my brother in law and it was a spark plug.

 

I sure would have looked at the ignition before tearing the motor apart but if you were going to do it anyway why not ... only thing is you probably still have the problem.. good luck

 

check the connections at the ign. module. un plug, clean with contact cleaner, and reinstall. i believe there was a t.s.b. on this. had it happen on my 00 flstf. steve

 

Yea I had the same problem with my 07 softie. Turns out when I was washing it the night before a toy's for tots ride i partially dislodged the connector to the coil and a half a mile from home it went from 2 cyl to 1 so I shut it off for maby 3 minutes and she started on 2 again then to 1. Then I found the loose connector. Nearly crapped my pants on that one. Good excuse for an upgrade anyways. Enjoy!

 

If it's fuel injected the ECM will cut out the cylinder if it reads the engine temperature is to high. You could have a defective sensor.