If it’s a motor mount tube it’s got to be welded on. You could have a 5/8″ aluminum sub plate made then use a Burris 3rd bearing top plate for a Yamaha mount. But I would think you could find a magnesium factory mount for it without too much looking. The factory mount would also use the Burris top plate.
FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience