Working on a 725 that has a pretty good oil leak coming from the top end. This is my father in laws and I was told it started to make noise so they shut it off and that is where I came in. I plan to work on it this winter and try to rebuild it. I looked at the oil and it looks good and the level is good too. I started it for a short time and it smoked bad. After it ran I was looking at it and I noticed oil slowly dripping on the side of the block where the oil filter is. I figure I would pull the motor and try to figure out what is going on. As I started to disconnect wires, belts and exhaust I notices there was only one bolt holding the engine to the frame. It looks like this has been leaking for some time based on the amount of oil and grass packed in the frame and around the exhaust. The engine is now out and ready to hit the bench this weekend to see if I can find where the oil is coming from. I am sure it is a seal but not sure what would cause it to leak from that location. It would be the upper seal on the crank since the engine is mounted horizontally. The mower has a little over 1000hrs on it so I am hoping I can rebuild it and get it back to them by summer. Any idea what would cause the oil to leak from this location and if anyone has done this and has some advice prior to digging into this that would be great.