Small Engines (Lawn Mowers, etc.): briggs enginr, hp briggs, internal passages

Question
i have a mtd 17 hp briggs rngine on a mtd mower.
it starts real hard and then dies sfter running good for about one minute . gas and spark seem good.

Answer
Assuming compression (valves leaking) is not the problem, as indicated by whisping sound from exhaust when turning over, it sounds like you need to clean the carb thoroughly, including using a piece of tag wire to push through all of the internal passages.  Before you proceed with that, try loosening off the fuel cap a little.  If the problem goes away the issue is with the fuel tank vent.  Hope this helps.