Redback and Big Tim have given you good advice.

Before you remove the needle valve, turn it all the way closed, and count the turns as you go. Let's say you get 2 1/4 turns. Now you can remove the Needle, put the cowl on, replace the needle and close it all the way - then open it 2 1/4 turns so you're in the right ballpark when you try to start the engine.