Standard for most modern two strokes I know is turn both high and low jet screws (on carb) all the way in, careful not to over tighten as you'll damage the seats and/or needles, now unscrew both one turn, most saws should run with this setting, if not adjust low speed little by little whilst turning over. Adjust low speed screw first - start saw, warm up and turn out screw till max tickover, unscrew another 1/4 turn and check it ticks over and revs freely, if not adjust slightly and rev again till it does. If it won't there is a possible problem elsewhere. High speed jet -briefly rev saw to max and listen, if saw is screaming jet is lean and using it like this will burn engine out very quickly - sometimes seconds. Turn out screw to enrich fuel/air mix. turning out screw will drop engine revs, depending on the saw this can sound quite different - I don't tune my husky and Stihls to sound the same, I tune my saws till I can just pick out a burble at max revs under no load and the Husky seems to rev much higher, try the saw on a good chunk of wood, if it struggles adjust screw, more fuel gives more power up to a point then saw just chokes. With domestic saws (MACs etc) I'd tune richer to be safe
TreeSmith, November 2010
