Small Engines (Lawn Mowers, etc.): B&G model number 28N707 15.5 HP, briggs and stratton, vapor lock

Question
I have a Craftsman riding mower tractor with the above mentioned engine.  The engine will start and run but as of late will not run past idle.  I have replaced the fuel filter and the line and checked for the vapor lock in the tank.  All work fine.  It is some years old and I am wondering where lies the problem?  It had done this in the past but only after a great deal of run time and the engine was warm.  Just two days ago I ran it with no problems for about 10 minutes and today it ran for about 20 seconds.  It will start and run at idle but not at operating speed.

Answer
 Hello Brian:

 Has the Carburator been Cleaned and Rebuilt? From your Description is Sounds like the Carburator has Trash in it. Soak the Carburator Overnight in Cleaning Solution(Gunk carburator cleaner) and then Blow Out All the Passages with Compressed Air. You can View this Engine at this Addy http://www.outdoordistributors.com/ and Click on the B. Then Select Briggs and Stratton. Then Select Dont have Part Numbers. Then Scroll Down to File # 28 and Click. Then Scroll Down to the Model Number and Click. This will Download a Breakdown/IPL of this Engine for you to View Online. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John