How Do You Adjust the Carburetor on a Weed Eater?

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Weed eaters are available in three different models depending on the type of tasks they’re designed to accomplish. Among these models include the battery-powered weed eaters, the electric or corded versions, and finally, the all-powerful gas-powered string trimmers.

In this post, we will learn how to adjust the carburetor on a gas-powered weed eater to help you save time and money by avoiding a trip to a technician.

Gas-powered weed eaters are perfect for accomplishing tough cutting projects, in suburban to rural areas. But they do come with a more complex starting and running checklist than their electricity-powered counterparts.

Now, what’s your first reaction when you discover that your weed eater didn’t start? Well, some people may decide to take it to a repair shop while others may opt to get rid of it and purchase a new unit. If you’re smart, however, you’ll do a little digging to find out the cause before you throw money away or waste time at the shop for an easy, at-home fix.

Before you run to the shop or the store, first check the air filters and the spark plugs for any clogged dirt, then check the carburetor. It’s pretty common for gas-powered string trimmers to need some regular maintenance and adjustments on the carburetor. They’ll build up gunk from the gas and dust in the air, and the adjustment screws can sometimes vibrate slightly during use and come out of ideal adjustment periodically. The same as cars sometimes need tune-ups, so do other gas-powered engines!


What’s a Carburetor?

Two-stroke and four-stroke engines are fitted with a special device known as a carburetor to help mix air and gas for efficient combustion. When gas and air are mixed in the carburetor, a powerful explosion is created and burns in the engine’s cylinder.

When air is sucked into the carburetor, it comes in through a narrow suction pipe known as a venturi. As air enters, a spray nozzle inside the carburetor releases gasoline creating combustion that produces power.

Now that you understand how a carburetor functions, this section will guide you through a step-by-step procedure on how to adjust this crucial part of your weed eater. Before we continue, let’s first check some of the adjustment tools you’ll require.

  • A flathead screwdriver
  • A special socket opener


Before Adjusting the Carburetor

The first step of troubleshooting the carburetor is to open the air filter to clean any clogged dirt or debris. This step is very easy to accomplish because it involves opening the air filter cover using a flat screwdriver. Next, check if the spark plug is working properly. Use a flat screwdriver to open the boot covering it, then use the available spark plug wrench to remove it.

Finally, if your trimmer has been dormant for quite a long time, the engine might not start due to overstayed or stale fuel. Simply drain the old fuel and replace it with new, “young” fuel for effective performance. If you start the engine and record a negative feedback, then it’s time to adjust the carburetor.


How Do You Adjust The Carburetor On A Weed Eater

When adjusting the carburetor of your weed eater, you need to locate the two fuel adjustment screws that are highlighted as HI and LO. That’s really all you’ll need for this process, in most cases.

1. Set the screws to the reference point

The HI screw is usually located on the right side of the trimmer while the LO screw is located on the left. Tighten both pf the screws all the way by turning them clockwise. This puts them in the same position as a reference point.

You can now adjust them both by loosening each by one full turn (counter-clockwise) and try to start the engine (open the choke).

2. Adjust the LO screw

Give it choke and try to start engine. If the engine starts, try to listen to if it’s sputtering or not. Usually, when an engine sputters, that means it’s receiving too much fuel from the carburetor.

To solve this problem, give it some throttle to keep it running and twist the LO screw in a clockwise direction one-quarter turn to ensure that the engine is idling smoothly. Once it idles well without throttle, it’s good on the LO screw.

3. Adjust the HI screw

Likewise, you’ll want to adjust the HI screw with FULL  throttle applied to ensure smooth running. To do this,  give it full throttle and adjust the HI screw clockwise in a one-quarter turn until the engine runs smoothly.

4. You’re done!

Now that you’ve followed each of these steps correctly, start your weed eater again and see if the engine runs smoothly. In the case that your trimmer develops more engine problems, the best action to take is to open up the carburetor to check for any holes or dirt in the valves. If you’re not comfortable doing this or you’re just too inexperienced with engines, this is the point where you might consider calling on a technicion to have it professionally assessed.


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