YT 18H Ford Yard Tractor. Model 9800688. dies?

I have a Ford YT 18H Yard Tractor. Model 9800688 It dies after running for abou 30 minutes. I changed plugs and fuel filter. Air cleaner and screen are clean. After it sits and cools off it will strat right back up and run for about a 1/2 and hour again. It dont miss it just dies and will not start untill it cools off.

Joe C
April 2011