I was looking around for someone to help with an oil leak on our Kitchenaid K55 when I saw your post. I don't know about yours, but if we remove the back cover on ours, there are three screws involved in speed contrtol. We had the same problem you describe, then adjusted the bottom screw, which helped, but adjusting the 2 at the upper corners (they had check nuts and springs locking them in place) got us to the speed we wanted in stir speed. I hope this helps. Joe
Joe, March 2006