I overfilled my B&S 725ex self propelled lawnmower. I cut front yard no problem. Yesterday I went to cut back yard. I realized I had overfilled it with oil. I drained oil refilled to proper level changed spark plug. Pulled cord it just won't start. Please help.
Pull the spark and make sure it's not wet with oil. If it is, clean it.
Validate there's not oil in the cylinder. If there is, you can squirt carb cleaner into it and pull the string a few times real hard to clear it out. Wash, rinse, repeat a few times.
Check your air filter and ensure it's not saturated with oil. If it is, clean and/or replace it as necessary to make sure it's not wet or oil soaked. If you do clean it, make sure it's not moist from water or a solvent before you put it back into service.
Those are the three top items I would check. You should be good. Of course, make sure your oil is at the correct level again. It never hurts to double check.