Sportster Custon 02. When the bike gets wet it will backfire and stall. For troubleshooting reasons I cleaned carb and filter. I washed the bike with Carb covered and it still backfired at start up. The plugs are new and gaped to spec. The next thing I was going to look at is the electical system by checking for voltage leaks in plug wires and coil. Does anyone have any idea what would be wrong? On a seperate note: The spedometer is all over the map and sometimes quits all together.

 

Cracked coil case, in the front between the towers. Been there, done that.

Get the bike warm. Get rpm's up to about 2,000-3,000 rpm's. Spray water directly on the coil front.