My guess is you probably can, do you want the pain and frustration of getting to fit and line up??????? But what do you call it YAKA........ YOUR CALL!!!!
I doubt it will fit, the mounts would be different on the frame, what's wrong with the Fizzer engine ? ( EDIT : Fizzer problem continued here http://2fiftycc.com/index.php?threads/fzr250-clutch-gear-problem.1318/ )