Hi. I'm ROn. I don't have much Knowledge on a yanmar ym240 but i have one I just got. There was no flapper valve on the exh. or an can so water got down the exh. I also have an 1948 ford 8n tractor and an 1952 dextra. i do know how to work on them. The farm is only 2.5 acr but I lone out the...