Both front screws are idle "mixture" screws used to create a "smooth" idle.
(these screws alter the idle speed a slight amount only--- not meant to set the idle speed)
Somewhere (on most all carbs) is a ***** located on the side of the carb as part of the throttle linkage.
This ***** pushes against a cam shaped (or notched) oblong washer, or just a flat spot.
This ***** sets the stop point of the throttle butterfly inside the carb throat.
Backing this ***** out will drop the idle speed.
Having said that.., if you didn't, re-check the timing with a timing light..., sometimes with a new
T-chain-n-gear set..., the timing will move. Too much "advance" will raise the idle speed as well.