Are these tubeless, and it's leaking around the stems, or is the tube leaking and it's coming out around the valve stem? Do R4's or ags require a different size rim? If you get the old tires off, maybe brush the rims, and if they are not pitted/corroded too bad, I would just weld up the old valve stem hole, and drill another in a different spot. Lot cheaper that a replacement wheel.