Sorry Guys, but I've been searching until my eyes bled. Some people had the same problem, but no one ever solves it or states what they found. Or it was dumb, like they had a bad fuse.

So, I have a 2006 FLHT I that has had the battery out for about 8 months while I raked, and did all the body pieces over. (it ran fine before disassembly)

I went to start it today and it farted and blew fireballs out the exhaust.

I checked the plugs and for spark and it is very intermittent. Like one yellow spark every 10 revolutions.

I checked the Crank Pos Sensor, the fuses, disconnected my Fuel Pack. Speaking of which I do get a fuel pump prime and I have 12v at the coil for those 2 sec.

Checked my ign switch and kill switch for continuity and no shorts. all good.

Checked grounds and the pos to the starter. Checked the coil for the correct ohms at the primary and secondary. Good.

I'm running out of ideas...

 

Hopefully it's something straight forward if it worked fine before.
Just wanted to check that you are aware that you'll get no spark with both plugs out due to the crank sensor needing to see compression. Need to use either a spare plug or a spark tester.
I'm not a fan of it but have you tried some easy start to see if it'll run off of it for a few seconds.? The flames you got suggests you had spark.
What is the voltage across the battery while cranking?
Don't know if you had any wiring disconnected but you're sure the plug leads are on the right way around at the coil, same with injector wires.