SOURCE: i have two screw settings on my echo hedge trimmer
On an otherwise healthy machine, the carb tuning procedure goes like this:
1) With the engine off, turn both mixture screws clockwise until they lightly "seat". Then turn them back counter clockwise two (2) full turns each.
2) Turn idle screw CCW and observe the throttle shaft movement. When it stops moving, the throttle plate is completely closed. From here, turn idle screw back clockwise two (2) full turns.
These initial settings should be sufficient to get a healthy machine to start up and stay running for the carb-tune procedure.
START THE ENGINE AND ALLOW ONE MINUTE TO WARMUP.
3) Turn the mixture screw closest to the engine (marked "L" ) clockwise in small increments (1/4 turn at a time) until the engine smooths out. Then back CCW until you have a slightly rough idle.
4) Accellerate to full throttle and turn the mixture screw closest to the air filter (marked "H" ) clockwise until the engine revs get higher and eventually begin to fall off again. Turn back CCW beyond ultimate top speed . . . until a very slight flutter is heard at top speed.
5) Release the trigger and adjust base idle speed until the blades barely crawl, then lower it one more touch.
6) Repeat steps 3, 4, and 5 once more and then check throttle response on quick rev-ups. VERY VERY small adjustments to the "L" screw in a CCW direction will give better response but larger adjustments will affect "H" settings.
That's it.
Special note for step 5: When you make the FINAL base idle adjustment, set it as high as possible without allowing the blades to move. This facilitates easier starts when warm.
Hope this helps,
Dolf-
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