I have a 6.5 HP Briggs and Stratton Lawn Mower from Sears. It has plenty of gas and a new spark plug. After I prime the gas it cranks immediately runs for 5 seconds then shuts off. I've heard that this may be because it sat for some time without being used. Any suggestions on what to do?

Probably Fuel or Carburetor, will need to clean.

Remove Carb And Clean Well.