Pull the carb, remove needle and inspect for any pitting, then wipe it down with some brake kleen. An AL carb sitting that long has corrosion issues, carb cleaner will not remove. That needle and seat are probably worn enough it's allowing fuel to leak. Have you checked the float? One sitting that long, if your rebuild kit didn't include one should be replaced.

With that many years lying dormant it may have been cheaper to replace it.