Small Engines (Lawn Mowers, etc.): rider dies after warms up, valve adjustment, fuel cap

Question
i had to fix the blade support under my craftsman rider.  i tipped it up on its back end and when i set it back down it would not start.  i cleaned the carburetor and it now starts but dies after 8 minutes of running.  any suggestions?

Answer
If the problem keeps recurring after 8 minutes each time, then the
carb is likely not the cause, but run it again, and when it starts to die, loosen the fuel cap, to make sure that it is not venting, and
a vacuum builds up in the tank until it starves the carb.
  If not, then I would suggest you check your mower's valve adjustment.  For me to go into any detail there, I need some model numbers off of the engine, or at least the tractor

 Thanks,

Fish