Small Engines (Lawn Mowers, etc.): Snapper Rear engine mower will not start, hp briggs, safety switches

Question
I have a 2002 snapper 281123bve rear engine mower with an 11 hp Briggs and Straton engine. After standing it up on end this morning to check the blade the mower will not start. It started fine before I stood it up on end. The fuel tank was full when I stood it up. I have checked to make sure it is getting a spark and fuel—both were fine. I also checked all three safety switches and all appear to be working fine. I even changed the oil. What else can I check?

Answer
I am assuming some oil got into the cylinder and the plug is covered in oil.  Remove the spark plug, CRANK the engine over a little bit to expel any oil that may be in the cylinder.  Clean the plug reinstall and you should be fine.

The engine will most likely some a lot of blue smoke to begin with, but after a minute or two it will clear itself up.