I don't know if sprockets from a yz450f will fit the wr250x or not, but I have a 56 tooth rear sprocket and chain from my old 450 that I don't need anymore. It's basically new and ill sell it cheap. Also have a set of front and rear SME axle sliders that have never hit the ground.

 

do the sliders fit? i plan on buying axle and frame sliders, sprockets, skidplate, fullthrottle handbrake with an r1 master most likely, easy pull and many more im not thinkin of right now lol!