How to use a 2 PTO shaft engine to add reverse to a go kart

[Ans213]

Hi, I would like to add reverse to my Yerf Dog, and I can across older engines that have two shafts, a crankshaft and a camshaft and that each shaft spin in different directions. The crankshaft spins counter clockwise ans the camshaft clockwise. Does anyone know how I can use one of these engines to add reverse to my go kart