Cleaning the debris off the carburetor before following this procedure will help you see the stamped markings on the side of the carburetor.
Do not over tighten the adjustment screws to avoid damage. Do not over adjust the mixture to avoid damage to the engine's internal parts.
Zama carburetors are found on many different types of two-cycle lawn tools, from string trimmers to leaf blowers and edgers. Typically as engines begin to wear a carburetor adjustment needs to be made. This delicate procedure, if not done correctly, can damage the engine and necessitate carburetor replacement. You will find three adjustment screws on the side of the carburetor. This procedure will take 10 minutes to complete.
Set the engine on a hard, flat surface. Locate the carburetor on the side of the engine, directly under the air filter. On the side of the carburetor are three adjustment screws; there are stamped letters beside these screws, "L" for the low speed adjustment screw, "H" for high-speed adjustment and "TAS" for the idle adjustment.
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Gently turn the "L" and "H" adjustment screws clockwise until they seat with the flathead screwdriver. Turn the "L" and "H" counterclockwise two full turns. Turn the "TAS" adjustment screw in clockwise until it seats.
Start the engine and allow to run for two to three minutes until the engine is at the operating temperature. Turn the "L" screw clockwise until the engine begins to slow, and then turn counterclockwise until the engine rpm's pick back up. Turn the "TAS" screw counterclockwise until the engine is at a steady reliable speed. Repeat the "L" screw adjustment above to ensure proper engine speed.
Advance the throttle to the FAST position, turn the "H" screw clockwise until the engine starts to slow, then turn counterclockwise until the engine speeds up and runs smoothly.