How to Fix a Hedge Trimmer That Dies At Full Throttle?

Why does my hedge trimmer die at full throttle?

If your hedge trimmer dies at full throttle there could be  an issue with the fuel supply, air intake that has been blocked by debris, or a partially blocked fuel line. A clogged spark arrestor or a spark plug, which is malfunctioning due to old age, are other reasons a hedge trimmer will die at full throttle.


hedge trimmer dies at full throttle



Since the introduction of ethanol-blended fuels, small engine repair shops make over 50% of their total income from replacing and repairing carburetors. Carburetors are responsible for feeding the engine with the right amounts of fuel and air. If your carburetor is clogged, damaged, or poorly adjusted, this could be the reason your hedge trimmer dies at full throttle.


Air filter

Air filters are responsible for cleaning and allowing air into the engine. It prevents debris from entering and harming the engine. As your trimmer ages, the air filter can get clogged. When clogged, the air filter may not allow sufficient air into the combustion chamber, which can cause your hedge trimmer to die at full throttle.


Fuel filter

A fuel filter protects your carburetor and engine by screening out impurities. Leaving old fuel to sit for a long time in your hedge trimmer can lead to a clogged fuel filter. Poor quality fuel or overuse can also affect your air filter’s performance. A faulty fuel filter will hinder the flow of gas, which will cause your trimmer to die at full throttle.


Fuel lines

Fuel lines disintegrate with time, and these small fragments may partially obstruct fuel to the carburetor. When the fuel line is partially blocked, it will not allow enough gas for full power, causing your hedge trimmer to die at full throttle. Therefore, you’ll need to examine the fuel lines for blockages or cracks.


Spark arrestor

A spark arrestor prevents hot exhaust particles from flying out of the engine. Sometimes, this mechanical device gets clogged up, hinders exhaust air, and prevents your trimmer from running at full throttle.


Spark plug

Spark plugs produce the spark that starts the combustion of the air/fuel mixture to produce power. Spark plugs can get impaired due to old age, oil buildup, or an inappropriate oil and fuel mixture. A defective spark plug can hinder your hedge trimmer from running at full throttle.


How to fix a hedge trimmer that dies at full throttle?

To fix a hedge trimmer that dies at full throttle you should clean, replace or adjust the carburetor. Other ways to fix a hedge trimmer that dies when giving it full throttle is to clean or replace the air or fuel filter.

While hedge trimmer models differ in design, the concept is the same. Therefore, with guidance from your instructions manual, you can fix these problems yourself. Follow these steps:


Clean/replace/adjust the carburetor

Carburetors create problems if they are clogged, corroded, or poorly adjusted.


Clogged carburetor

Fuel left in the carburetor for a long time evaporates and leaves a thick sticky substance that blocks the tiny passageways inside, much like dirt. This causes an air/fuel imbalance, also known as a lean condition. If you notice any blockages, you need to clean the carburetor.

Spray carb cleaner inside the carburetor with the engine running or disassemble the whole thing for a thorough cleaning.


Corroded or damaged carburetor

If your hedge trimmer is considerably old, then the carburetor could be damaged or corroded. To find out, disassemble the carburetor and check it against a carb kit for flaws. While you can replace minor parts like weak springs, I suggest replacing the whole thing if the main housing is damaged or corroded. Make sure to clean the fuel lines and the fuel tank too.


Poorly adjusted carburetor

If your carburetor is poorly adjusted, it deprives your hedge trimmer of the correct air/fuel ratio to perform at high RPMs. Different models have different adjustment screws. I suggest you refer to your instructions manual for guidance during the adjustment.


Clean/replace the air filter

To examine the air filter, remove the cover by popping it open or removing the attached screws. The air filter is commonly situated above the carburetor. Next, replace the air filter with a new one and fasten the cover. Your trimmer should start running normally if the air filter was the problem. Replace the air filter regularly to avoid such issues in the future.


Clean/replace the fuel filter

Perform a visual examination of your fuel filter or blow through one end to check for blockage. If the fuel filter has smelly fumes and appears dark inside, clean it or replace it altogether. If you left old fuel in the trimmer, drain all the fuel before installing a new fuel filter. Replace fuel filters regularly as part of your maintenance schedule.


Clean/replace the fuel lines

First, drain all the gas from the fuel tank. Then, disconnect the fuel lines from the fuel tank and the carburetor. Blow air through the lines. If you notice any abnormalities, replace the lines. Fuel lines are a safety concern since they can ooze fuel and cause a fire.


Clean/replace the spark arrestor

The spark arrestor is usually fitted in the exhaust or muffler. Open it with a wrench and examine it for carbon deposits. If the screen is too dark in color, you need to clean it. Heat it with a propane torch and use a wire brush to remove the remnants. You can also replace it if worn out.


Clean/replace the spark plug

Regularly examine your spark plugs for corrosion and other abnormalities. First, disconnect the ignition wiring from the spark plug. Remove the spark plug and clean it using sandpaper or a carb cleaner. Replace it if it has more than 100 hours of operation, is worn out, or is damaged.

If you have followed the above steps and your hedge trimmer still dies at full throttle, you may want to check your ignition module and gaskets for abnormalities. However, these are not common problems and may require advanced knowledge to fix.

At this point, it is advised you hire a technician to repair your hedge trimmer.


Why are my hedge trimmer blades not moving (locking up)?

The reason your hedge trimmer blades are not moving is due to a broken or loose clutch, faulty gearbox, and damaged blades.


The clutch prompts the gearbox to spin at a specific rotational speed. Without the clutch’s input, the engine will not engage the gearbox. If your trimmer engine runs but the blades don’t move, the clutch could be loose or broken. For a broken clutch, replace it. Refer to your user manual for the correct clutch size and disassembly guidance. You can also engage a local technician to fix it for you.



The gearbox is usually directly attached to the trimmer blades. With continued use, the gears wear out or get damaged. The best remedy for this problem is to replace the damaged gears.



It’s common for twigs or debris to get caught up in trimmer blades and hinder them from spinning freely. The blades have teeth that can bend, especially if they come into contact with a hard surface. Damaged blades will most probably stop moving.

To solve this problem, first, ensure your engine is off. Disconnect the plug from power as an extra precaution. Now, remove any debris lodged in the blades. For damaged blades, replace and lubricate them before using the trimmer again.


Why does my hedge trimmer only run on full choke?

Air and fuel supply problems are the reasons your hedge trimmer only runs on full choke. With air and fuel supply issues, the most common culprits are gas caps, carburetors, fuel lines, and fuel filters.


Some hedge trimmer models have a gas cap fitted with a valve that allows a good flow of gas. If this cap is clogged, it interferes with the fuel supply which causes your trimmer to only run on choke.

To troubleshoot the gas cap, start your engine and loosen the cap halfway and turn the choke off. If the engine doesn’t die, then the gas cap is malfunctioning. Remove it and clean it with soapy water or replace it.

For the carburetor, fuel lines, and fuel filter, examine them for any cracks, leaks, blockages, or loose connections. Then, clean or replace them depending on their condition.

If the problem persists, check or replace your primer bulb and gaskets. Always use the recommended fuel quality to avoid such issues in the future. Also, note that 2-stroke engines should run on choke until they attain fast idle.


Why is STIHL trimmer over revving?

The most common reasons behind your Stihl trimmer over-revving are poorly tensioned throttle cable, stuck governor assembly, and a poorly adjusted carburetor.


Throttle cable

If the throttle cable is poorly adjusted, the throttle plate will not close fully in an idle position. As a result, your trimmer will have a fast idle. Check the throttle and correct any irregularities in it with guidance from your instruction manual.


Governor assembly

The governor flap assembly can also contribute to over-revving issues in your trimmer if the flap is not moving freely. Try moving the flap manually to check if it’s operating normally. Identify what’s causing the flap not to move and fix it. It may be broken parts or the tension spring.



A poorly adjusted carburetor will cause a lean condition, leading to over-revving. You can use the H (high), L (low), and idle screws to fine-tune your trimmer. The screws are not always similar for different models. Refer to your instruction manual to identify and adjust the screws.


Why does my STIHL trimmer die at full throttle?

Stihl trimmers are designed to use a mixture of gas and oil and ff the oil-to-gas ratio exceeds the limits, the STIHL trimmer may wobble and die at full throttle due to poor combustion. The other common reasons are:


Dirty spark plugs

Spark plugs may develop carbon deposits from poor combustion, worsening the problem. Check your spark plugs for flaws and clean or replace them. Stihl recommends you replace your spark plugs after 100 hours of operation.


Choke overuse

The choke starves the carburetor of airflow to achieve a lower air/fuel ratio in the combustion chamber. The choke lever should always be at the “choke” position when starting a cold Stihl trimmer. As the engine starts running, immediately turn the choke to the “off” position to allow airflow.

Your engine will shut if you open the choke too late because of too much fuel in the combustion chamber.


Clogged spark arrestor

The oil/gas mixture used in Stihl trimmers clogs the spark arrestor screen with carbon deposits much faster. This is a common problem with the Stihl FS 38. Clean the spark arrestor regularly to avoid engine stalling at full throttle.


Clogged fuel filter and gas cap

A dirty fuel filter or a clogged gas cap hinders fuel flow to the engine. This can cause the engine to stall at full throttle. Examine both components for blockages and clean or replace them if necessary. Blocked vents in the gas cap are common problems in most Stihl models.


Clogged or poorly adjusted carburetor

Most Stihl carburetors are factory-set at sea level and may require adjustment at higher altitudes. Carburetors have been common problems in many Stihl models, especially FS 38. Clean your carburetor using carb cleaner and refer to your instruction manual to adjust it.


Why does my Husqvarna trimmer die at full throttle?

There reason why your Husqvarna trimmer dies at full throttle is because of substandard fuel or a clogged spark arrestor. Clogged or poorly adjusted carburetors and dirty air filters are other reasons why your Husqvarna trimmer dies at full throttle.


Fuel issues

Since the introduction of ethanol into fuel in 2009, small engines have paid a heavy price. The alcohol in the gas creates gum and varnish which blocks tiny air and fuel holes. This creates an air/fuel imbalance which causes small engines to die at full throttle.

Ensure you always use manufacturer-recommended fuel quality. Don’t let fuel sit in the trimmer for more than 60 days. Also, clean or replace the fuel filter and fuel line as per the manufacturer’s recommendations.


Spark arrestor

A clogged spark arrestor screen is a common cause of trimmers stalling at full throttle. Open the muffler exhaust area and use a wrench to unscrew the spark arrestor. If it has carbon deposits, burn the screen with a propane torch and clean it with a wire brush.



A clogged or poorly adjusted carb will create a lean condition which can trigger your Husqvarna trimmer to stall at full throttle. The remedy here is to clean the carb thoroughly or replace it altogether. Follow the instructions manual to fine-tune it.


Spark plug

A clogged spark plug hinders the combustion process and can cause your Husqvarna trimmer to die at full throttle. Clean or replace your spark regularly as recommended by the manufacturer. If you’re using a non-resistor spark plug, replacing it with a resistor plug could do the trick.


Air filter

An old air filter may be clogged, starving the engine of air and interfering with air/fuel balance in the combustion chamber. Regularly clean or replace your air filter to prevent your trimmer from dying at full throttle.


Why does my Ryobi trimmer die at full throttle?

The reason why your Ryobi trimmer dies at full throttle is because there may be a shortage of air or fuel supply in the carburetor. To identify the source of the loss of air/fuel, you need to examine your air filter, fuel filter, fuel nozzle, carburetor, and spark arrestor.


Air filter

A dirty air filter will not allow enough air to the combustion chamber resulting in your trimmer stalling when throttled. Clean the air filter with soapy water, rinse and let it dry before reinstalling it. You can also replace it, it’s inexpensive.


Spark arrestor

A dirty spark arrestor screen will hinder your trimmer from achieving full RPMs. To solve this problem, replace the spark arrestor screen or clean it with a wire brush.


Fuel nozzle and fuel filter

Fuel nozzles/filters may get clogged, especially when exposed to old or substandard fuel. They’ll then hinder gas from flowing to the carburetor and create a lean condition that affects the performance of your trimmer at full throttle. Clean or replace the parts depending on their condition.



A poorly adjusted or clogged carburetor deprives your engine of the correct air/fuel mixture. This affects the performance of your engine, especially at full throttle. Adjust your carburetor for optimal air/fuel mixture.

Refer to your instructions manual when doing this because some Ryobi models like the EX26 and RY253SS have their adjustment screws not so obviously located. If the problem persists, clean or replace your carburetor