My uncle has an older model articulated Husqvarna mower with a 17.5 ohv Briggs&Stratton engine. I can't find a model # on it anywhere as the engine cover is missing and the seat has been changed. My question is, it has stopped pulling. It will not go forward or reverse. The drive pulley has dropped down to where the crankshaft is just spinning inside of it. 1-Is there a keyway in this pulley? 2- How do I acces the pulley to service it? Any help would be greatly appreciated.