Small Engines (Lawn Mowers, etc.): craftsman 20.5hp tractor, briggs and stratton, craftsman

Question
craftsman tractor 20.5hp briggs and stratton model 461707 will not restart after it heats up

Answer
How long does it take to heat up?  Is it running properly before you shut it down?  Does it quit while running or are you saying you mow for a bit until its warm, shut it off and then it wont restart?  

Please provide me with a little more information