OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Scott Bonnar Original Engine - Rebuild or Replace?

You should not be able to insert the metal strip anywhere around the fibre disk. If you can, the breather is worn out.

1. Did you clean the breather before taking that picture, or was it already clean?
2. Was the disk stuck to the metal, or could it move back and forth (transverse to the surface of the disk, not laterally)?

If the disk was crudded up and stuck, and you cleaned it and freed it up, we have an explanation for your oil-from-the-breather-hose problem. If it was pristine and working, we cannot blame the breather valve and have to consider uglier possibilities for the problem (like a broken piston, for example, since it happened suddenly).