Posted this in the Softail section and tslonige told me post here and ask you Dawg. Any ideas??

The specifics:

He has a 2000 Fatboy, carbed. He rode it about 1 -1/2 months ago before parking for winter. Half tank of gas. Two weeks ago he got it out and rode a short trip then washed it and covered it back up. Yesterday he goes to start it for a quick ride on the finally dry streets only to have it backfire through the carb and pipes. After looking he found the plugs were fuel fouled. Cleaned and re-gapped them and it started for a few seconds before again backfiring.

Tonight we pulled the plugs and checked for spark. Check! Fuel was not a problem. Check! Thought maybe a stuck float and needle wide open so it's probably flooding. Pulled the air filter and the lower part is soaked with fuel. Removed the backplate and dropped the bowl. Float seems to move freely so we buttoned it back up, cleaned the plugs and cranked with them out to try and air out the cylinders. Put the plugs back in and tried to start again. This time a HUGE backfire through the exhaust including a 6" flame. This screams out of time to me but why from just riding then parking and nothing happened in between?

Also, he was told a sensor at the front on the primary side would not allow the bike to jump time. My thing is, I think it may be electrical related to the SPARK timing, not the engine timing. I'm thinking he got something that controls the coil wet and shorted out causing it to send incorrect info to the coil.

Anyone have any thoughts?

 

Replace the plugs with new ones, before you go any further.

You can clean them all day and still be fouled. (and they don't cost much).

 

Ditto,bad plugs are still bad plugs after they are cleaned.