I have a 1956 TEA20 Fergy. Unfortunately its starter motor has died. I have bought one from a local supplier who claims it is the correct one but it has a shorter shaft and only 9 teeth. The original (I know so because it is stamped with the date 1956) has a longer shaft and 10 teeth. Does anyone know whether the one I have bought will work or it will it stuff up the starter ring?