Small Engines (Lawn Mowers, etc.): Craftsman push mower wont start, hp briggs, crankcase breather

Question
Hello, and thanks for your time! I have a 6.5 hp Briggs Craftsman push mower (#378381) that I can't get started. I recently changed the blade and had it on it's top (I know..probably a bad idea), and haven't gotten it started since.  I noticed a little oil on the floor afterwards.  The plug looked to be fouled, so I put in a new one and put in fresh gas too.  No luck.  At first, it would sputter a little, but now I can't get it to go at all.  Thanks in advance for your response.

Answer
Tipping the mower one way or the other is always a problem.  One thing to think of is that if you tip it so the spark plug is up there will not be a problem.  

Sounds like you have oil in the breather box.  Remove the crankcase breather and drain.  It is a small metal rectangular box with a hose coming out of it.  It will be in the top, flywheel area, of the engine.  Next check the oil to be sure there is still enough in the engine or that it is overfilled with gasoline.  It will get there when tipping over the engine.  Next check the air filter.  It may be oil and gas soaked from tipping.  Replace it. If the plug is real oilily try to get the engine to run even on choke and try to burn out the oil.  If you cannot remove the head and clean cylinder of oil.  You may need to replace the plug again after getting it started.  Hope this helps