Don,

Dan may be right that your engine is not getting enough gas. Check for
possible vacuum leaks around the carb by spraying carb cleaner at obvious
connections while the engine is running. If there's a vacuum leak the engine
will suck in the cleaner and stutter or die.
Also, check the needle valve adjustments. My guess is that you've
adjusted the carb too lean or air is entering by a vacuum leak. These are
both easy to fix.

Dave M.