My son has several good small engines 25cc's whatever. Wants to make a friction drive . I have no knowledge of these. I would guess the roller has to be a certain size for the engine etc. Anyway where to start looking for the engine mounts? As mentioned earlier, he has the engines and I said would try to steer him in the correct direction on getting a mount and here guessing rear drive. Thanks and hopefully you can point to a jobber who handles these. gphil.