my 2005 1200 custom started backfiring out of the blue but only the front cyclinder replaced gaskets.plugs,plug wires.checked coil,dumped out the gas got fresh gas in it,compression check.got a new ICM mod. in stalled new battery bike turns over like starter drags and the engine light blinks.i can put the old ICM back on and it cranks right up but still backfires.I have no codes to go by.anyone got an idea?

 

you didnt post what mods you have on the bike... could be fuel settings or timing. accel or decel?
do you have the shop manual?

 

Was the crank position sensor ever replaced?

 

yes and the same thing with old ICM the bike starts but still backfires. the new ICM module it turns over slow and engine check light blinks but does not start changed out the icm,crank poistioning sensor,new wires, plugs,comp.checked,gaskets,fresh gas,new battery,and checked coil,was told need to program new icm so the data link can sink with sensors,they can pull up codes i pull them up and it comes up none.2/16/2005 taking bike to harley shop tomorrow have it programed and codes pulled find out whats up with the old girl.

 

I had a similar issue, difficult start, backfire from rear cylinder... fixed with crank position sensor and intake gaskets, but you've already done that. I'm leaning towards an electrical gremlin for your troubles. The only things remaining are the voltage regulator and stator. Possibly a short in the wiring somewhere also.
Good luck and let us know what you find.