I've worked on an 'Autoshift' bike, the kind with the weights on the rear wheel that controled shifting. I even had to take it for a test ride. My advice; If you ever come across one, run, don't walk, away from it. They are cheap in every sense of the word. And the ride is horrible. It will shift when you least expect it, and it is jarring. Cheaply made would be a compliment for these things.