Jul 5, 2013. #14. im 5'8 170+ all geared up, 125 works for me, I do casual (for fun) mx and trail riding, if you think you want more power than your YZ250f go to a 250, if the power is good for you get a 125. If you ride sandy tracks quite a bit, I don't recommend the 125. Also, bare in mind that 2 strokes require rejetting fairly frequently ...