wow I just finished rebuilding that exact model number for a customer.
I guess the place to start is to ask how long has the carb been sitting? If it's any length of time at all the gas will gel up, get gummy and all the adjusting in the world won't clear out the air bleeds and all the other passages where the gas needs to pass through correctly.
The carb I just did only sat for about 18 months and needed a fresh rebuild. Runs perfect now.
BSE Racing Engines