Needle and seat or a bad float are the culprits for flooding when not running.
Sounds to me like you missed something else in the rebuild. Your sintered bronze weep plug in the bottom is clogged up. Go to Roberts carb website and look up the parts for a M John Deere. It will fit your carb. Take the carb back apart and tap the old plug out with a pin punch that will fit through the hole. Tap the new one back in with a larger one. Barely tap the edge 4 places around the new plug with a sharp chisel and put it back together.
Should your needle and seat or float fail again the gas will drop out of that plug and you will see it.