Guessing here, but could be because it's either getting too much air or not enough gas, thus it only runs when you choke the air to get things back in a balance that works. That is, it's running too lean.
I'd check for air leaks(at carb, or between carb & motor) or fuel line blockage issues. Too little gas/to much air will make it run hot, you don't want to burn up a piston.