I have a 2002 Ultra classic with the 88 c.i. twin cam in it. I was riding the other night and when I pulled onto my street the piston stopped firing. It started back up at the edge of my drive way. I parked it and a couple of days later it had a hard time starting. When it did start it was running on the rear piston only. Thinking it was the spark plugs, I gaped new ones to .40 and changed them. Same thing, only running on the rear piston. I removed the the spark plug, held it to the frame, and hit the start button. It has spark. Any suggestions?????

 

 

3 things are needed
compression,
gas
and spark-
I am going with Ranger 73, fuel as a first guess.

 

I hate it when that front piston acts up.

But seriously, why not pull out the ol' service manual and your volt/ohm meter and start troubleshooting the ignition system? Plug wires, coil, etc? Also fuel delivery as mentioned. CPS also.

Or I guess you could just keep replacing stuff and maybe you'll stumble across it.

 

Pass the envelope?

 

Mine's a 94 so it's carbed, but when I lost spark to one plug I swapped plug wires at the coil and the spark moved with the wire.
Indicating 1 side of the coil failed/

 

Since he clearly states "I removed the the spark plug, held it to the frame, and hit the start button. It has spark." I doubt it's the coil, plug or wires.....
The engine needs fuel, air, spark and timing. I'd start by swapping the injectors to see if the front cylinder runs and the rear cylinder doesn't.

 

If the spark moved with the wire, wouldn't the other wire be bad?

 

No, I moved it at the coil end. The wire on the rear plug won't reach the front plug smart ***.

 

The 02s don't have a CPS. Did you mean CKS? Plug wire, plug, coil, and ECU/ignition module for spark. If EFI, injector or injector wiring. Carbed? Probably not fuel if running on the other cylinder. Next would be compression.. Remember, you need pressure, spark and fuel to fire a cylinder.