just been re reading this, the 86 500 doesnt have a detachable subframe........if you cant fix it by welding in a piece of steel you need a full frame, but I wouldnt use an 85 125 frame, not sure if its same size.the 85 and 86 kx250 and 500 frames are the same, apart from not having a mounting for your rear master cylinder on the 85 models as these had drum rear brakes. Surely a good local fabricator can sort it if you havent got acess to the gear? K.