I just bought a 2003 cr250 that looks to be in great shape. He claimed it had low hours, and it seems like it does. It has good compression and starts first kick every time. Even in -15 degrees celsius. (5 degrees F) On my first ride with fresh gas, mixed at 32:1 with opti 2 cycle oil, it seemed to run great. The second ride I notice a rattle in the engine when just cruising at half throttle or speeding up through the mid range. Today I took it out for a ride in the snow and realized something was wrong. When riding in the snow, it seemed I couldn't even rev it too little or too much without the engine rattling. Usually I can ride good low and high, but in the middle of the power accelerating or cruising, it rattles a bit. But now it rattles A LOT. It still idles fine without any noise. I just payed fully for this bike with the cash that I have saved up for 5 months. When you just spent $2000 on a bike at 15 years old, you sh*t your pants. I really would appreciate feedback. And before you mention it, my dad was with me and looked over the bike when I bought it.