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How to Adjust the Carburetor on a Weedeater

line trimmers image by Horticulture from

Gas weed trimmers keep your lawn and garden looking crisp and beautiful. Using a trimmer often will require adjustments to the carburetor to keep the trimmer running at top performance. The trimmer typically will have three adjustment screws on the back of the engine. The best way to adjust the carburetor is to reset the adjustment screws and start from scratch. The engine will have a chance to burn carbon that builds up within the exhaust as you adjust the carburetor.

Set the weed trimmer upright on the ground, with the head guard on the ground and the bottom of the engine on the ground.

Using a flat-head screwdriver, turn the high- and low-speed adjustment screws clockwise until they fully seat. The high- and low-speed adjustments screws will have an “H” or “L” beside each screw. There also should be an idle-adjustment screw below the two other adjustment screws.

Turn the high and low adjustment screws counter-clockwise one full turn with the screwdriver. This will give you a starting point for the remainder of your carburetor adjustments.

Press the primer bulb three times, and start the weed trimmer. The trimmer should stay running without you pulling the trigger and giving the engine gas. Turn the low-speed adjustment screw counter-clockwise until the trimmer will stay running without you having to pull the trigger.

Hold the gas trigger down, and adjust the high-speed adjustment screw counter-clockwise until the engine will run continuously without hesitation.

Release the trigger, and allow the engine to idle. The trimmer head should not rotate while idling. Turn the idle-adjustment screw counter-clockwise until the engine idles and the head does not move.

Adjust A Zama Carburetor

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 procedure will take 10 minutes to complete. Locate the carburetor on the side of the engine, directly under the air filter. 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. Start the engine and allow to run for two to three minutes until the engine is at the operating temperature. 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.


Always keep hands away from the trimmer head while adjusting the carburetor.

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