Its a Honda XR50 in '04 they changed the name to CRF50. They do all kinds of crazy stuff with these things, not to mention there are a million parts available for them to make them hold larger riders. They are actually for kids in stock form. Check out
www.cycletrader.com you can usually find used ones going for around $800 or so.
They run about $1300 or so OTD new from your local Honda ATV and motorcycle dealer. Do some searches on google for fiddy, XRfiddy, XR50, and what ever else you can think of. These things are HUGE! And the arent just for off road, they stunt these things all of urban neighborhoods.
Dang, I cant wait to get one.
Im trying to find a cheaper used one, but all that I have found have already been sold.