any age!,there's no age limitAdded: It must be assumed that the bike is street-legal and you are of age to be licensed. Otherwise you may not ride it anywhere off of private property.
You need to be at least 4 or 5. A good bike for 4 and 5 year olds would be an 50cc. From 8 to 11 a jr80 or crf80 would be good. from 10, 11 and 12 something like crf100s or cr80s.
some people say you should be atleast 16 to operate one, but i know some people who started riding when they were 5. so it really is any age practically long as you follow the rules and wear all the...