Small Engines (Lawn Mowers, etc.): Mower with a 6 HP Brigg & Stratton engine wont start, briggs stratton, hp briggs

Question
I have a Craftsman 6 hp (Briggs & Stratton Model # 12H802-2639-B1) 21" multi-cult rotary lawn mower.  It is ~ 4 years old.

The mower will not start.  I have taken off the carburetor and cleaned it off.  No obstructions or defects can be found.  The spark plug has been cleaned off.  There is a dry, black soot on the plug which I cleaned off.

Before I removed the carburetor, the mower would just quit and not start for a while.  When it would run it would last for no more than 40 seconds.  After a day of this the mower no longer starts.

Answer
Hiya Arthur
Quick check- squirt some fuel directly into the carb- see if it will start.  

If it starts for a sec- you next check will be to drop the bowl and verify you can control the fuel flowing in by raising and lowering the float.

If thats ok- get a can of carb cleaner and spray directly up the center tube in the bowl, look for evidence of spray entering the throat of the carb (this checks your jets)

Lastly- make SURE your gaskets good between the carburator and the engine block- heck go get a new one N put it on they're cheap.
Lemme know how this goes ok?