After about 30-45 minutes it will die and will not run. You can start it with the choke, but it dies as soon as you put it on run, so I assume it is a fuel problem. Rebuilt the carb and cleaned it several times. Cleaned the tank and fuel line. Replaced the fuel filter and air filter and spark plug. Any ideas?

Sounds like you have a clogged fuel cap and its not letting your take to vent . This is called a vapor lock.
Luck

Cleaned cap and drilled vent hole larger. Tried mowing and started dying after about 40 minutes . It was a good try, anyway. Back to square one.

Sounds like you need to look at the carb , maybe let some one that knows how they work look at it.I'm not trying to be mean , but it sounds like your about ready to blow it up.. I have had to take these carbs apart and soak over night in strong carb cleaner more than once , you can hand clean them but that's not good enough.
Luck