Lawn tractor can be started normally and run fine for about twenty to thirty minutes, even with the blade engaged. After that time engine will start to lope and reduce (throttle level wide open and off choke) power until it finally quits.

After cooling down for about 15 minutes it can be restarted normally and will repeat paragraph above. It seems to be heat related.

DID:
1. Changed and gapped spark plug.
2. Check for bad gas. Clean carb bowl.
DID NOT:
1. Change fuel filter, Fuel selenoid, magneto.
HELP

Check fuel tank cap , make sure it is venting .
Luck

To DG: Clearing gas cap worked. Thanks