Once you've done the free mods to the wrf (throttle stop, grey wire etc) the only difference in power is cam timing and the pipe. The stock jetting is different but doing the free mods is going to require rejetting too. The wrf also has a heavier flywheel, wide ratio transmission and softer suspension which wouldnt be good on the track. If you don't need the estart, it's probably easier to get a yzf and modify it a bit to work in the woods as well as a track. That's what I did anyway.