What size dirt bike best fits a 9 year old boy..?

50cc . They are not small and have a lot of power

Ummm?!?!? willie up there aa what the hell are you talking about? haha. Okay buddie back to the question....I am 13 and i am 5'3 and i ride a ktm 105sx. you sound like your a biggener. to get a lot of hieght off ramps its not the kind of bike you have its how well you can ride it. Me i have been racing for 8 years now and i have won numeres championships but the best bike would be a yamaha 85. That bike is very durable and fast and you would have a real good time on it. No critizem to the other answers but if you are a biggener than a 150 expert is way to much for you and you would get really hurt on it. And you want a bike that you dont have to wrench every night. That is why i am not recomending my ktm 105 because they need alot of mantnece

Go 80cc. will last him until his teen years and should fit him now.

TT-R 90