I have done this. It will work. Use your original KDX Knuckle, and swap over the lever. You can then use the old KDX lever as a hockey stick, or put it back onto the KX. I have a 1996 KDX engine in a 1996 KX 125 chassis. I do have a bit of a clearance problem with the kicker rubbing the pipe. On my old frame (1996 KDX) I had no problem with clearance.