there is considerable difference between the K&B "40" , "60" many remember from the 70's and the SPORTSTER series. for one, the carb is a crap shoot . you may have one work well, the next , total junk. I had a sportster carb on a regular K&B 40 & idle /transition was IMPOSSIBLE. finally bit the bullet & purchased perry carb-TOTALLY new motor! also sportsters were designed with low power user friendly ( with exception for the carb) on trainers they work well. I would NOT use it where you need power , such as on a fighter.