My buddy has a walker that is only a few years old and has less that 300 hrs on it. Last year he let someone use it, and they let the oil run low, thus blowing the engine. He could not afford to fix it then and has since got out of the business. I am going to buy it from him and put a new engine on it. I have used it before, but cant remember if it has a 16 or 18 kohler on it. How compatible are the different engine sizes when replacing a engine on the walkers? If it were a 16magnum, could you put the CH20 on it? Or does the replacement engine need to be the same one? Im getting this mower for almost nothing so I dont mind spending the money for a new engine. I have been looking around at prices, any suggestions on a good place to order a new engine cheap?