Why is My Hedge Trimmer Bogging Down

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Is your hedge trimmer slowing down, stalling or sometimes refuses to start at all? Maybe you can get it running for a few minutes but then it suddenly stops. While this can be frustrating, it doesn’t mean you have to take the trimmer to the repairs. With some know-how you will learn the causes and how to get your hedge trimmer running continuously.

If your hedge trimmer keeps bogging down, there is probably something wrong with the spark plug or carburetor. An engine that starts and suddenly stops can also be due to a faulty gasket or fuel line.

Clogged Air Filters

The air filter allows air to reach the engine while blocking out debris. This ensures no dirt or particles get inside the hedge trimmer. Eventually though, the air filter gets clogged with dirt, which prevents air from reaching the engine. You can find the air filter atop the carburetor.

Without enough air the engine cannot start properly. You may be able to ignite the engine, but it will lose power when you go full throttle.

How to fix it. Remove the air filter cover. Depending on the hedge trimmer, you may be able to just lift the lid off or have to use a screwdriver.

Now you can take out the air filter and clean it. Most air filters are cleaned every 2-3 months, but you should adjust this depending on how often you use the hedge trimmer. If the air filter is too dirty, replace it with a new one. With the Dewalt 20V MAX* Cordless Hedge Trimmer for instance, only low maintenance is needed.

Carburetor Problems

The carburetor plays an important role in gas powered hedge trimmers, so any problems will affect its operation. Here are some examples:

  • If your hedge trimmer starts but dies when you increase power, the carburetor needs some adjustment.
  • A dirty carburetor can cause a lawn edger to bog down.
  • A hedge trimmer will not run with a damaged carburetor.

If the carburetor is damaged, a hedge trimmer may not start at all. In some cases you may be able to power it up, but the engine will expire soon after .This can also cause hedge trimmer blades to get stuck, though there are other reasons why this can happen .

How to fix it. Shut the trimmer down. Look into your owner’s manual for the carburetor’s location. Usually it is under the air filters. Take the air cleaner cap off.

Look for anything that might be clogging air circulation. If the carburetor is dirty, now is a good time to get a carburetor cleaner. We suggest the DESIN Carburetor Cleaner Tools Kit as it has pretty much all the tools you will need.

If dirt is not the problem, it could be the adjustment settings. Check the manual for the location of the adjustment screws. Adjust the screws incrementally and test the hedge trimmer. Tweaking these will adjust the air and fuel mix so be careful.

If that does not work, check the carburetor idle screws. Here is how to do it.

Step 1. If necessary, refer to the user manual to find the idle screws. They will be marked H (for high) and L.

Step 2. Turn the H and L screws in. This shuts the fuel off.

Step 3. Turn both screws the opposite direction twice (two turns). This is going to restart the engine. It might sound like the engine is having a hard time but it is fine.

Eventually the engine will run as it usually does. When it reaches that point, let the hedge trimmer idle for 60 seconds.

Step 4. After idling, turn the low screw (marked L) clockwise to boost the fuel level.

Step 5. Rotate the H screw clockwise with the engine running at full power. If you followed these steps, the hedge trimmer will no longer bog down. Make sure to clean the carburetor regularly to prevent dirt buildup. If these steps do not work, the carburetor is damaged and must be replaced.

Worn Out Gaskets

The gaskets function as sealants to keep fuel and air from getting into spots they should not reach. Located below the carburetor, a faulty gasket can cause the engine to stall or start and stop repeatedly. Severe damage leads to incorrect air / fuel mix and stall the trimmer. This is why you need to fix this problem right away to avoid complications.

How to fix it. To get access to the gasket, you have to take the air filters out. Next, use a wrench to remove the bolts on the carburetor. Examine the gasket and check for signs of cracks or tears. Worn out gaskets should be replaced right away. You cannot clean the old gasket by the way, it has to be replaced.

Fuel Filters

Hedge trimmer fuel filters prevent dirt and debris from reaching the engine. However these filters get dirty and clogged which can cause a lawn edger to stall.

How to fix it. Look into the fuel tank and you will find the fuel filter connected to the fuel lines. Use a hook or similar tool to take the filter off.

Examine the fuel filter if there is anything clogging it. You can attempt to clean it but the better option is to install a new one. After you add a new fuel filter, turn the hedge trimmer on again and there will be no more problems.

Image Credit: Mark Hunter

Fuel Line Issues

The fuel line makes it possible for a hedge trimmer to use fuel. This only works if the line is clean, otherwise the trimmer will start and stop. You can either clean the fuel line or replace it.

How to fix it. To do any checks, disconnect the fuel line from the tank and carburetor. This will require some effort, and the process varies depending on the hedge trimmer. Consult your owner’s manual on how to remove fuel lines. Once you have done this, blow into the line and see if there is any clogging. If there is blockage, replace the line.

Spark Plug Problems

Spark plugs literally do just that, provide the spark to ignite the air and fuel mix and start the engine. A damaged spark plug is one of the most likely reasons why a hedge trimmer cannot run on full power.

How to fix it. You need to examine the spark plug for signs of cracks or corrosion. Unplug the connecting harness and the wire off the spark plug.

Carefully lift the spark plug and look for damage of some sort. If the spark plug is covered in oil, clean it and then try the hedge trimmer again. If it works, the spark plug was just dirty.

If you see corrosion, rust, cracks or other damage, replace the spark plug. Please keep in mind that hedge trimmers work with specific types of spark plugs so use the model number when shopping for a replacement.

Other Reasons Why Hedge Trimmers Bog Down

If the fixes above do not work, there could be other reasons why. You should also check the user manual troubleshooting guide.

  • Oil leak. If the engine is leaking oil, there won’t be enough power to run it. Turn on the engine and check for any leakages or spills.
  • Dull or damaged blades. Trimmer blades turn dull with constant use. Use a file sharpener to keep them working. If your hedge trimmer blade is not moving, they could also be misaligned or need replacement.
  • Damaged engine. If a single component is broken or clogged, your hedge trimmer may not run or run poorly. This is why regular maintenance is so important.
  • Wrong fuel mixture. Hedge trimmers only work with a specific fuel mix ratio. If your mixture is off the tool will not run correctly. If you believe this is the problem, empty the fuel tank and prepare a new fuel mixture.
  • Old fuel. Old fuel turns sticky and unusable. Worse, the sticky stuff spreads throughout the engine and clogs everything. If your hedge trimmer engine is having difficulty, check the fuel. If you see old fuel everywhere, clean it up and pour a new mix into the tank.