I had an 02 RM 250, the only problem I had with the bike was the top of the piston above the rings on the exhaust side broke off. I did end up having to get a new cylinder which was $450.00. They are a little pricey on cylinders. Other than that, the stock seat foam breaks down after a while and gets pretty mushy. Those were the only problems I had, but I loved the bike. I have an 03 RM 250 now, and I had a similar piston problem. This one didn't break, but it cracked. Both pistons were the original pistons in the bike. I have been running Yamalube at 32:1. I don't know if this is a manufacturing problem with the pistons, but wanted to give you a heads up.