im thinking about getting an f4 track bike, and i was wondering if an f4i motor will fit on its frame, or anyother fuel injected motor

 

A little confused by the title of the thread 'F3??' as you are asking about F4's

The F4i should in theory fit in the F4 carbed frame as far as i am aware, both being ally framed.

The F4i engine wont fit in the F3 steel frame.