Question: what is the difference between a twin cam?
Answer: Pictured below is the major difference between a Harley Davidson Twin Cam "A" & "B" motor (other than the engine cases being different etc..) This is the balance system found in the Harley Davidson Softail motors from 2000 - present. There is no balancing system in the Twin Cam "A" motor from a Dyna or Touring bike.