Zama makes a little "Z" shaped thing to use to set needle height. I usually don't take the plug out unless the thing was really dirty inside. Although some carb manufacturers don't recommend soaking them in carburetor cleaner I do anyway, for a short while. Generally about an hour or so. Don't soak the little spring or the plunger, the spring might disappear. That usually cleans them up inside all the little crevices enough after rinsing it in hot water and gently blowing the thing dry with compressed air. I think Zama has a website with all info on it.