Please state which saw you are referring to.
If your carb is fully adjustable, it will have not one but three screws.
L = low speed jet
H = high speed jet
.... and a third screw that is idle speed.
Some saws do not have an "H" adjustment, which is a bad deal.
Here is a tutorial on carb tuning
Madsen's tuning guide
For the beginner, a tach is helpful until you develop an "ear" for tuning. A good saw tach costs about $100, though.
To complicate things, most new saws have limit caps on the tuning screws. You'll have to deal with the limit caps, at a minimum pulling the cap and cutting off the "ear", then reinstalling the cap (if it survived the pulling process).
You mentioned your screw was all the way clockwise. That doesn't sound good.
Read the tutorial, let us know what saw you have, and check back with more specific questions. It takes a while to learn to tune a saw, but you kinda have to learn because saws don't have electronic computer controlled fuel injection like cars. The carbs do need to be tuned or else you will not achieve maximum power and/or the saw may run too lean and eventually seize.
