Well, I picked up my 2000 Fatboy earlier this year and have pretty much been plagued with the rear cylinder plug fouling out to the point of the bike becoming unrideable within @ 100 miles of operation. I've been through the carb and cleaned it out, along with the tank (had it cleaned out at an Indy shop due to rust). Slow jet is a 45, mid is 2 clips up and main is an 85. Added an in-line fuel filter. Ran, same problem... Had the Indy shop check out and set the carb with their computer/analyzer. Ran, same problem... pulled intake and checked seals, no problem, replaced, of course, same problem. I pulled a compression check today and both cylinders checked at @ 90 initial and went up to @ 145 psi. Went ahead and cheked with a shot of oil to each and the pressures were about the same. The rear cylinder does have light black smoke on start-up and smokes light black smoke when I hit the throttle. The front plug is relatively clean with little color change. Black on rear plug is sooty, not oily. I'm at the point of thinking the valve seals are gone...The bike only has @ 10, 000 miles on it. Ideas?