I found an 07 YZ450 for sale. The seller claims less than 20 hours on the bike, and said he rode it in 5 MX races. My question to all of you is: how much damage could have been done to this bike in such a short time? I can buy it for $4,000. It sounds like a great deal, and I really want to upgrade from my '98 YZ400. But I don't want to buy it, then spend $$$ fixing it. I need your opinions. What kinds of problems could I be in for if I take the risk and buy it?