I just bought two Xr 50. I is a 2002 XR and the other is a 2001 XR. The 2002 Xr 50 top speed is a lot slower compared to my 2001 XR. The 2001 is all stock and runs really well. The 2002 is more of a project bike it runs and has an after market exhaust. i though it ran ok until I got the 2001 and the 02 will not keep up. It does seem like there may be smoke out the exhaust, I am thinking it may need a new piston and rings but not sure. I am new to 50s and have only had one dirt bike in the past any help would be appreciated.