i dont know of anyone who has, but i know of people within the club who are fitting r1's into their 126 correct me if this is wrong but im sure theys aid they are fitting x2 r1's. Wern't R1's the fastest bike at one point??
Somwhere on this forum is a link to a video of a fiat 500 with a bike engine, not in a pretty state but very nippy!!!
Chris