Small Engines (Lawn Mowers, etc.): B&S 3.5 wont stay running, blown head gasket, oil trail

Question
Paul-Feel certain you can help me on this.  I bought a McClane reel mower with a B&S 91202 Model 3.5 hp engine on it.  I've cleaned the gas tank & Carb and replaced the diaphram in the carb (also the plug...just for grins).  The most I get is a few seconds of running while I try to spray carb cleaner in the carb while I'm yanking the cord.  Engine sounds fine for those few seconds!  I clearly have a fuel delivery problem but don't know what else to try.  Any help is appreciated!  

Answer
Instead of sucking air through the carb your engine is sucking outside air through either a blown head gasket or a poor seating intake valve.   Pull the head, you will have to do this for either problem, if the head gasket is blown you will see an oil trail where it was leaking.

Difficuty level, changing a flat tire with a crappy tire iron.