Look at the carb needle and seat. Need to pressure test both making sure you are not flooding past the carb needle/seat.
Pull the oil stick and SMELL for fuel. If you smell gas, repair the needle/seat. Needle/seat must pass a pressure test for 30 minutes.
Check carb float height. Most are set too high and will make it run rich.
6mm spark jump, is that the max distance you saw spark jumping? So if you opened the gap up more she would die?
Hope you are testing for spark WITHOUT the plug inline. If you are running resistor plugs, will make your spark weaker. You can Ohm out the resistor. Should be roughly 4,500 Ohms. Anything over like 8k or more, replace the plug.
Recommend non-resistor plugs in small engines.