Small Engines (Lawn Mowers, etc.): 5.5hp Toro Push Mower, new spark, spark plug

Question
I've got a 5.5 hp Toro push mower.  I prime it and pull once or twice and it starts with no probolems.  Problemis after it starts it only runs for a few seconds and then cuts out.  The oil has been changed, air filter cleaned, and new gas put in it.  I've also put in a brand new spark plug and that didn't change anything.  Any suggestions?

Answer
 Hello Gerald:

 It Sounds like the Carb needs to be Cleaned and Overhauled. The Main Jet isnt Pulling Gas through it. Gas Left in teh Carb over the Winter has Turned to a Varnish Like Substance and is Clogging the Jet. Hope this Helps. Let me know what Happens, Please.

 Good Luck

 Respectfully

 John