I think there could be a significant market for Kalkhoff ( Duma ) motor replacements. I have perfectly good Kalkhoff Tasman which my wife uses but after the second replacement the third is showing signs of stress. I had given thought to replacing the motor/controller with something potentially more reliable. I can fabricate stuff ( I built my own track car ) and I know a master welder. However as has been pointed out post welding heat treatment is a significant issue so this really needs to be a bolt on via an adapter plate. No idea of the dimensions involved or the most suitable replacement. If I can find the time I could DIY but if there was a kit I would be first in line! Bearing Man?