I have an S U Eliminator ll carb on my 77 FXE. I get a big belch through the carb now and then, thinking it was lean I began to richen the mixture, turning in the screw. The belching is all but gone but it is now turning the plugs black.(too rich) I Have not rejetted it yet. Should I? Or should I just swap it for an S&S? C'mon guy's and gals, What do you suggest?