I have a stock 91 Electraglide. While on a 2000 mile ride and noticed soot on my exhaust pipes. It has a BUB exhaust.( it is not a true dual). While I was on the road I replaced the air filter thinking that might be the culprit. I rebuilt the carb not that long ago. 4000 miles. When I accelerate hard black smoke comes out the pipes. ( mostly the right pipe). The plugs look good. Light tan to gray. I pulled the carb apart and replaced the float needle. The rubber came off of the rebuild needle very easily. I thought maybe the float was hanging up. The float adjustment is correct. While I had it apart I cleaned and blew out everything. It's still blowing black smoke. The plugs aren't that old. Maybe 8000 miles. I don't know what could be causing the soot. Any help would be greatly appreciated. I always use Sea Foam. Thanx. Bus Driver.