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Bob - The carb 3 screws are the high speed and low speed mixture and idle RPM adjustments. They're probably marked H, L and I respectively. (If not marked, "H" is farthest and "L" is closest to the motor, and "I" is the mechanical stop screw that limits throttle plate travel.) To rough set the carb before tuning, set "H" and "L" both 1 turn open. Now look down the carburetor throat and turn "I" in or out until you see the throttle plate is completely shut (it stops moving). Then give it about 2 turns clockwise. This should be sufficient to get the motor running. Now try to start the motor using full choke. If after several pulls you don't get any results, open "H" 1/4 turn and try again. Repeat until the motor starts. Once the motor runs, slowly open the choke and adjust "H" as required to keep the motor running. After the motor's run a couple minutes to warm up, adjust "I" as to get a reasonable idle speed (i.e. the chain stops moving), then adjust "L" to maximize idle RPM, then slow the idle back down with "I". It'll take 2 or 3 iterations of the above to find the optimum settings for "L" and "I". Once the idle is set, pull the throttle trigger quickly. If the motor stumbles or stalls the high speed mixture is too lean - open "H" 1/4 turn and try again. If the motor runs rough, won't achieve full speed and smokes excessively, "H" is too rich - turn it in 1/4 turn and try again. Repeat as required until the motor picks up quickly and smoothly when you snap open the throttle. Finally apply a load (saw some wood) and see how it goes. You'll probably fine you need to open the "H" 1/8 to 1/4 turn more from the previous setting in order to achieve maximum power under load. Once the "H" is set, go back one more time and tweak "L" and the "I" for the best idle and to insure the chain stops when the trigger is released. Hope this helps...
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