Stuck open (needle out) Motor floods and won’t run. Way rich, no adjustments effect it.
Stuck closed (needle locked up in the hole) Motor runs out of fuel and dies.
If your running a carb that has developed problems after running fine for some time, change the filter, remove all jets and blow air through all hole in the jets and carb itself, change pump completely or just rebuild. Also check tank pickup and all fuel lines for kinks or blockage. Lot’s of the karts with age tend to wear out the pickup in the tank, rubber gets hard and crack, ect. Still got problems, change plug, ignition, reeds, inspect piston, you know the drill.