Most replacement carbs are jetted too lean. 2 options:
1) Replace the main jet with the one from the old carb.
2) Drill out the main jet with the next size larger drill. If it still doesn't run correctly go up one more size.
1) Replace the main jet with the one from the old carb.
2) Drill out the main jet with the next size larger drill. If it still doesn't run correctly go up one more size.