Lawn edger carburetors are set by the factory. Most manufacturers require no further adjusting, while some do require adjustments after the first 10 hours of operation. Because there are so many manufacturers, there is no one way to tune the carburetor. If the edger is not operating as it should or you're not getting good fuel economy, there are some things you can generally do to tune most carburetors without taking them to a repair facility. Don't force any screws that won't turn readily--this can cause damage.
Remove the air cleaner cover, which is near the carburetor. Some have a knob you turn counterclockwise to remove the cover, while others have a screw you remove with a flat-head screwdriver.
Pull the air filter out and clean it in a solution of dish soap and water, if you have a foam filter. Rinse the filter in clean water and squeeze out all the excess water. Allow it to dry fully before reinserting it into the air cleaner housing. If you have a paper filter, replace the filter with a new one. Place the cover back over the housing and secure it with the knob or retaining screw.
Look for a spark arrestor near or on the muffler. The spark arrestor is usually a small plug with a screen. Pull the spark arrestor out with needle-nose pliers and clean it with a stiff toothbrush. If there are cracks or the screen is excessively dirty, replace the spark arrestor with a new one. Install the spark arrestor back in the engine until it snaps into position.
Search for the adjustment screws, if any, on your carburetor. The screws are on the carburetor and will point to the rear of the motor. Some edgers have only one screw, the idle, which has an “LA” or “I” next to it. Other edgers have up to three adjustment screws. These often have an “H,” “L” and “T” letter designation near them.
Place the edger down with the handle on the ground. This keeps the edger blade off the ground. Start the edger and allow the motor to warm to operating temperature. This usually takes five minutes. Turn the “LA” or idle screw on single-adjustment models clockwise with a Phillips-head screwdriver until the motor runs smoothly and the edger blade doesn't turn on its own.
Turn the “L” screw all the way clockwise until it no longer moves, on models with three adjustment screws. Slowly turn the screw back counterclockwise until the engine runs smoothly. Turn the “T” adjustment screw counterclockwise until the edger blade stops rotating under idle--if the edger blade rotates while under idle.
Squeeze the edger's trigger to full throttle and hold it for 10 seconds, then release the trigger. If the engine speeds up without hesitation, no adjustment to the “H” screw is necessary. If there is hesitation, hold the trigger to full throttle and turn the screw clockwise until the engine begins to sputter. Quickly turn it counterclockwise until the engine begins to run smoothly.