The 220s are notorious for eating stock pistons, so that may be the problem. If so, then I would recommend a complete rebuild. Wossner has a rod and piston (the 200 and 220 use the same rod), so you can get parts for them. The motor (and bike) didn't change for 10 years, so other parts shouldn't be a problem. I have a 220 in my kx/kdx hybrid. They are a lot of fun to ride, and make a great buddy bike. If you can get it for a low enough price, it might be worth it.