First get all the bikes systems up to a good baseline. Things like a clean airfilter, valve clearance, cam chain tension, points adjustment and timing, spark strength, spark plug condition and gap, charging system checked out, etc. Part of the baselineing would also involve your carbs . . .Float level should be set to stock specs, bench synchronize your carbs, and assuming your bike is stock, make sure that the idle air screws are clear and at the initial stock settings, needle clip position and main jet are all to stock specs. Warm up your bike, guage synch your carbs and adjust the idle air screws for maximum idle rpm. If all the bikes systems are working properly and assuming that you have a stock setup you should not be running rich anymore. If you still have rich looking plugs then go back and find out which of the bikes systems is not baselined correctly. Don't make the mistake of trying to treat the rich "symptom" with carb tuning (changes to the clip height and main jet size etc) until you are certain of your "baseline". Carb tuning is typically required for bikes with modified intakes, exhaust, engine displacements etc where the stock carb specs are no longer valid. The plug chopping method mentioned previously will give you an idea of whether your have a rich or lean conditon at a particular throttle setting and thereby tell you which carb "circuit" is involved with the particular condition. It is possible for example to be rich at idle, lean in the midrange and rich at WOT so examing the plugs carelfully at a particular throttle position is key to making the proper carb adjustments.
