ya stay away from the big headr pipes unless you have done a piston and cam. my dad has an 01 xr650l and mine is 05 xr650l. we are both jetted(mine 160 main dyno jet kit) and he has an white bros e1 series silencer and i use an e2 series. but he has a white bros headr pipe and mine is stock hheadr pipe. mine runs away from his, especially on the bottom. take it for what its worth. later!