Motorcycle Repair: Carberatur, harley davidson sportster, dyna jet

Question
How do you adjust richness & leaness on the 1999 1200cc Harley Davidson Sportster Motorcycle ? I am experiencing an occassional backfire at low speeds and twice it has shut itself off at a stoplight and then had to sit turned off before it would start again . I want to know if the richness and leaness is the problem or might it be something else ? Please give me any ideas if you think that the richness and leaness isn't the problem. Keep in mind that it doesn't do this ALL the time , only occassionally and usually only in heavy traffic . I have changed the spark plugs and the oil but nothing else.
Thank you VERY much ,
          Devin Watts

Answer
TO adjust the richness and leaness you have to change jets int he carb. Your bike came from the factory lean to pass EPA standards. The best way to correct thins problem is to install a Dyna-jet kit. Its pretty easy and has good directions, so you should be able to do it yourself. Should stop the backfire.
Good luck and happy riding
Mike