How to Adjust a Weed Eater Carburetor

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A healthy carburetor is key to the performance of your Weed Eater. Weed Eaters or weed whackers sometimes require a carburetor adjustment as the screws may loosen due to vibration. Other things that can affect the carburetor are a change in your fuel mixture or trimmer head. Both may cause a different load on the engine.


Most Weed Eater trimmers use what's called a two-stroke engine. This means oil is added manually to the fuel.

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Find the Fuel Adjustments

The first step to adjusting your Weed Eater's carburetor is finding the two fuel adjustment screws. These are located on the body of the carburetor. These two screws are typically labeled HI and LO.


The HI, or high, screw allows you to adjust the fuel when your string trimmer is at full throttle. The LO, or low, screw allows you to adjust the fuel when the engine is idling.

Adjust the Carburetor

Now that you've located the HI and LO screws, it's time to get down to business. Turn both screws clockwise until just tight. Now, rotate the HI screw one-and-a-half full, counter-clockwise turns using a tool with a spline tip. This tool is similar to a screwdriver, and you'll need it in order to adjust the screws on the carburetor. Ask the local hardware store if you're having trouble finding the correct tool. Next, rotate the LO screw one full counter-clockwise turn.


If being this precise is difficult or not working for you, simply take it slow. Every time you give the screws a quarter turn, stop and check if the machine now works. You can repeat this step over and over using trial and error until the machine begins working.

Let the Weed Eater Cool Down

Once you've adjusted the HI and LO screws and gotten the Weed Eater to work, you must let it cool down for several hours.


After this waiting period, turn it back on to see if it's still working. If not, you may need to clean the carburetor. This involves prying the carburetor open and inspecting it. If there's a gummy fuel buildup inside, it's time to give it a thorough cleaning.

Clean Out Your Carburetor

Remove the breather plate (the black structure covering the outer side of the engine) from the engine of your Weed Eater. This will expose the carburetor. To clean it, separate the two fuel lines that connect the carburetor and the fuel container to each other. Remove any connected cables. It's important to remember which cable goes into which hole when it's time to put the carburetor back together.



Now, find where the jets are and pull them out. After doing this, you'll see that there's a spring and washer attached to them. Don't lose these items! Unscrew the retaining plate that's holding the primer bulb to the primer base. Once this is removed, you'll see the diaphragm and screen. This is where you'll likely see signs of gum clogging up the carburetor housing. This gum is what's preventing fuel from getting into the carburetor.


Now, unscrew the fuel pump diaphragm. Next, take out the screw right near the needle seat and use your thumb to stop the needle seat from eventually falling off once the screw gets loosened. The needle seat should also be removed. Now the carburetor is ready to be cleaned. Place the carburetor housing inside a vat of ultrasonic carburetor cleaner for 15 to 30 minutes. Once the carburetor is sparkling, put everything back together in reverse order.


Test the Weed Eater

If you've put the machine back together correctly, it should work. If it doesn't, get the advice of a small engine professional who can diagnose the problem and/or fix it for you. Something more serious may be wrong, and it may be time to purchase a new string trimmer.




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