Sounds like a vacuum leak between the carb and engine.
Mike

Does it run at high speed?

Yes..Mower will run at high speed. But sputters and stalls when at idle.

I was able to find the problem. Turn out to be a stuck choke valve. I removed the entire carb and cleaned it. There were a lot of build up grime and dirt in the inside of the carb bowl. I noticed one of the springs on the valve was covered with dirt and was restricting the valve to open freely. A good spray of carb cleaner and an air hose did the trick. Problem resolved.