I am considering buying a dirt bike for my son's 10th birthday. He currently has an electric Razor dirt bike that tops out at 17mph. What suggestions do you have? I am considering a Yamaha PW80 3 speed auto trans or a Honda CRF80 F with 5 speed standard transmission. My son is on the smaller side at about 4'4'', 25'' inseam. Any advice or suggestions? 2 stroke vs. 4 stroke? Auto trans. vs. standard trans? Seat height?