im pretty sure you caant widen the rear axel let alone replace a stock one because its shaft driven i think you may just have to leave it how it iss lol and as far as the brake i dont think so because on a chaiin drive atc there are little teeth taht the disk slides onto and the original axel for a 250sx does not have sorry buddy. i had a two fifty sx i tried to mod it as much as i could all i was able to do was weld a fmf silencer on it and new plastics and blue lights everywhere lol let me know if you need any help by the way i got some brand new fenders for the 85 sx im tryin to sell my my 250sx got stollen almost two years ago fenders are just sitting in my closet brand new black leather seat too!!
ThReE WhEeLeRs ArE NoT ThE cAuSe Of PeOpLe GeTtInG KiLLed, NoT KnOwiNg How To coNtRol OnE is WhAt KiLLs.
Legalize atc's!!