may be the whole assembly will fit from another model , may be a later shaft might fit with a few mods , know any one with a later model kx250 you could look at , may be go to a wrecker and see if you could compare shafts, i cant see it being to different , part numbers will be different from the smallest difference , it just a matter of finding a later part and comparing and seeing what can be done. let the site know what u find?
