After warming up the engine at part throttle for a couple of minutes, clear it out with a 3 second burst. Then idle the engine.. If the chain rotates, turn the idle speed screw to the left (CCW) until the chain stops.
Turn the LO NEEDLE slowly to the right (CW) to find the fastest engine speed. If this causes the chain to rotate, repeat idle screw adjustment to stop the chain from rotating.
High speed (with throttle wide open). Set needle 1-1/4 turns open, checking for smooth acceleration by opening the throttle wide for 3 seconds. If the saw stumbles, turn needle to the right (CW) 1/8 turn @ a time until smooth acceleration is obtained. Try a saw cut to see if adequate power is available. Continue making 1/8 turn adjustments (CW) until saw shows a power drop when asked to cut. (This indicates too lean a mixture setting.) Then, from the setting in step 3, turn the HIGH NEEDLE 1/4 turn to the left (CCW). Check the cutting ability of the saw again. This should be the best setting for your particular altitude, temp. and humidity conditions.
To pre-set before initally starting the saw, turn LOW and HIGH and IDLE screws in gently till each one just stops. Then turn each out (CCW) 1 - 1 - 1 1/4 turn.
Hope this is helpful. Try www.zamacarb.com/tips.html
Select the "Tech. Guide"
Good luck and God Bless.