I agree with Jared. Stay away from the 85's, and don't let anybody talk you into one just because it may have an over sized front wheel. I have seen that a few times, usually more in the 4 stroke 125's though. It's just a trick to get the bigger taller kids to buy those bikes, and you will out grow it within six months.
A 250f, whether it be from Honda, Yamaha, Suzuki, Kawasaki or KTM, would probably be your best bet. I have a 2 stroke 125, and although it is just as fast, I hate having to mix the gas and oil for the bike. I always forget the ratio (I don't ride that much anymore). All you need is unleaded gasoline for the four strokes, and oil is added separately in the bike.
Get out there and have some fun.