I have a '08 WR250x supermoto with 3500 miles in very good shape. I am thinking about trading it for a '09 YZ250f that has no mods and 31hrs. YZ is in pretty good shape. Can tell its been ridden but said it had a mechanic do all the work (heard that before). KBB show fairly even in price but mine is worth a little more. I am concerned buying a 4t with 31 hrs and not knowing anything for sure on bike's history. I know mine is in great shape and don't want to get messed over. Thoughts?