Some of the later ones have an annoying super restrictive baffle in the muff. Cut the front of it off or drill the spot welds and pull it out to defeat it. The earlier saws have no baffle which makes a mm easier (enlarge the opening under the cover or add a side port with deflector). Set the carb to 13,700-14,000 no load for a stock saw with mm. If you have no tach set it to 4 stroke as soon as you lift up in the cut.