definitly either a 250 two stroke or a 250 four stroke.. you could probably ride a 450 four stroke, but they are heavy...
im a girl im 5'5 and i weigh 130 i ride a 125 two stroke... its a little too tall for me and probably has more power than ill ever HAVE to use... so that should help you out a little bit.... my boyfriend is about 6' and he is i think 185 he rides the following - 250 two-stroke, 500 two stroke, and IF he were to ride a four-stroke im sure itd be a 450...