Chainsaw Keeps Cutting Out. Tips From a Professional:


Chainsaws generally cut out after starting because the engine gets too little or too much fuel from the carburetor. A chainsaw that keeps cutting out can be a source of severe discomfort as it wastes your time and worries you about your chainsaw’s health. Issues that usually cause a chainsaw to keep cutting out include bad fuel, clogged carburetor, fuel lines, etc. Fixing these issues is usually not too difficult, meaning they can be resolved at home.

Chainsaw Keeps Cutting Out:

In general, a chainsaw that starts but keeps cutting out is because the engine is not receiving the required fuel and air to keep it running.  To fix the issue, check, clean, or replace a dirty air filter. Clean or adjust a dirty spark plug, clean the carburetor, clean/unclog the fuel line, and drain and replace old/bad gas.

Checking and fixing these issues is not really difficult. In this blog post, I will provide you all the information and tips on why your chainsaw keeps cutting out and how to get it working perfectly.

Why Won’t My Chainsaw Keep Running?

A “cutting out” chainsaw starts fine but fails to stay running beyond a couple of minutes. This is also known as “stalling.”  Your chainsaw keeps cutting out or stalls when its engine doesn’t get enough gas and air to keep it working fine. In most cases, this happens because the fuel supply to the engine becomes interrupted. To fix an engine that keeps cutting out, all components that deal with the fuel and air delivery have to be checked, cleaned, or replaced.

The most important of these components is the carburetor. It takes air and fuel, creates the correct air-fuel mixture, and sends it to the combustion chamber. The fuel lines and filter provide clean gas at the required rate to the carburetor. The air filter makes sure that the air being supplied to the engine is free from dirt and debris. Finally, the spark plug ignites the air-fuel mixture in the combustion chamber at regular intervals. All these components work together to ensure that the engine works well. But if some of these components fail, the engine fails too and cuts out.

How to Fix a Chainsaw that won’t Stay Running:

Now, let’s see how to check and fix the earlier mentioned components:

● Chainsaw that won’t Stay Running: Check and clean the Air Filter

A chainsaw’s air filter prevents dirt and debris from entering the engine. However, wood particles and debris can clog the filter over time, hindering the airflow. Regularly checking and cleaning your chainsaw’s air filter is needed to fix this problem.

A chainsaw’s air filter is well protected and hidden from the user’s eye. The best way to determine the air filter’s position is from the slits at your chainsaw’s surface. Slits are there to ensure an uninterrupted airflow in and out of your saw. However, in extreme cases of debris accumulation, the slits become shielded from the inside by dirt particles, which can seriously harm your saw.

Once you have located the air filter, use a screwdriver to remove its outer covering. Next, take off the main filter cover present beneath the outer cover. This will give you access to the air filter. Make sure you carefully remove the air filter.

If your machine uses a foam air filter, you can wash it. You need two buckets of water and a hand bristle brush/toothbrush to clean it. Put some drops of soap in a bucket filled with hot water and swirl to create foam. Take the filter, softly scrub it with the brush to release the dirt particles, then dip it in the hot water bucket.

Swirl it in soapy water to allow the soap to absorb and pull the dirt out. Let it stay in hot water for a couple of minutes, then remove it and dip it in the cold water bucket to remove any remaining dirt particles. Let it sit in the cold water bucket for a few minutes, then take it out and let it dry completely before reinstalling it.

I recommend replacing a damaged air filter. If your machine uses a paper air filter, you can not wash it. So when dirty, it always needs to be replaced.

Before reinstalling the filter, you should also clean the air filter cover since air has to flow through the covers to reach the filter. Place the two covers in the hot water bucket, scrub them with the brush, and then wash with cold water. Let them dry. Once the filter and its covers have dried completely, reinstall them. Install the filter, then the inner cover, and finally the outer cover using a screwdriver.

● Chainsaw that won’t Stay Running: Check and clean the Fuel Filter

The fuel filter in your chainsaw can be found inside the fuel tank. The fuel filter’s job is to prevent dirt and debris in the fuel tank from entering the fuel lines. When the fuel filter is damaged, dirt from the fuel tank can freely enter the fuel lines creating a clog and preventing the fuel from freely reaching the engine. The fuel filter itself can also get clogged. A clogged fuel filter stops fuel from entering the fuel lines, and eventually, from reaching the engine, causing it to cut out.

If your engine keeps cutting out, check the fuel filter for damage and clogs. Replace it when needed. Check your chainsaw’s manual for correctly removing the damaged fuel filter and installing its replacement. I recommend replacing a damaged fuel filter instead of fixing it. It is not an expensive component and is easy to find.

● Chainsaw that won’t Stay Running: Check and clean the Spark Plug

A dirty or faulty spark plug is another well-known reason causing your chainsaw to keep cutting out. Remove the spark plug and check if the insulator nose is covered with oil, carbon, or fuel deposit. When the live electrode of a spark plug becomes covered, voltage flows along with the insulator nose back into the metal shell and grounds out rather than connecting the gap between the two electrodes to fire as usual. As a result, the spark plug starts missing, causing the engine to cut out.

An inaccurately adjusted carburetor usually sends a rich fuel mixture to the combustion chamber, resulting in the spark plug getting dirty over time. Suppose your chainsaw’s spark plug is really dirty. I recommend replacing it. A spark plug that is not too dirty can be cleaned with a metal brush or sandpaper.

I recommend checking the spark plug gap as well. If the spark plug gap is not correct, adjust it.

● Chainsaw that won’t Stay Running: Check and clean the carburetor

The main culprit behind a chainsaw engine that keeps cutting out is usually a dirty or wrongly adjusted carburetor. A faulty carburetor fails to supply the correct air-fuel mixture, also called the “charge”, to the engine. Causing the engine to cut out or stall. If you have already checked and cleaned the earlier mentioned components, but your chainsaw is still cutting out. Check and clean the carburetor.

– Cleaning the Carburetor:

  • Step 1: Clean the intake components: Using bad gas can result in a gummy residue build-up in the carburetor intake. Gas can get bad when it is older than 1 to 2 months. Use some carburetor cleaner spray to clean the intake components.
  • Step 2: Wash the needle valves: Deposits can clog a carburetor’s needle valves. Use an appropriate carburetor cleaning liquid to wash the needle valves while gently scrubbing with a toothbrush. Let the needle valves dry before moving on to the next step.
  • Step 3: Pull the pull cord: Blend the gas in the tank with some cleanser liquid and pull the cord several times with intermediate pauses. Even though your chainsaw will not be running during this process, pulling the cord like this will cause some fuel-cleanser mixture to run through the carburetor. Wipe off the sticky residue that was clogging it.
  • Step 4: Add fresh fuel: Drain the old fuel from the tank and add fresh fuel. If you do not expect to use your chainsaw for more than a month, add some fuel stabilizer.

The above procedure can be used if the carburetor is mildly dirty. However, if the carburetor is really dirty or too clogged. Then, you’ll have to disassemble it and clean the individual components.

– Adjusting the Carburetor:

Most chainsaw carburetors have three adjustment screws:

  • Idle speed/throttle adjustment: The idle speed adjustment controls how much the throttle valve stays open when the throttle trigger is released. If the idle speed adjustment is too low, the engine cuts out as soon when the throttle trigger is released. However, if the idle speed adjustment is too high, the high idle speed will engage the centrifugal clutch. Causing the chain to run. This can be a hazardous situation.
  • Low-Speed Fuel Adjustment: The low-speed fuel adjustment controls the fuel proportion in the combustible air-fuel mixture at idle speed. If this adjustment is too high, the mixture becomes too rich. This causes the engine to load up and cut out at idle speed. However, if this adjustment is too low, the air-fuel mixture becomes too lean, causing the engine to cut out because it is starving. This adjustment is mostly marked as “L” on the carburetor.
  • High-Speed Fuel Adjustment: The high-speed fuel adjustment controls the fuel proportion in the combustible air-fuel mixture when the chainsaw is running at cutting speed. If this adjustment is too high, your chainsaw will fail to reach the RPM level essential for it to reach maximum power. Furthermore, it will cause a sluggish throttle response, smoking, and performance loss. If this adjustment is too low, the engine will likely reach an RPM level that can cause cylinder seizure and bearing failure, and the cutting power will decrease too. This adjustment is marked as “H” on the carburetor.
This is how you can adjust your chainsaw’s carburetor:

Once the air filter has been cleaned and you have added fresh fuel (add at least half a tank), you can start with the carburetor adjustment by balancing the high and low-speed screws. To adjust the carburetor, make sure that both the high and low-speed screws are completely turned in as soon as your chainsaw becomes hot. Then turn each screw counterclockwise one rotation, or gradually, depending on the manufacturer’s manual. Next, turn the high-speed screw clockwise to make the mixture lean. Finally, turn the high-speed screw counterclockwise until the engine runs fine. In this setting, you have achieved the correct RPM for your chainsaw.

You can also use the throttle adjustment to perform a quick test. For this, ensure that your chainsaw is idle and the chain is not moving. If the chain is turning, gradually turn the throttle screw counterclockwise until the chain stops turning.

● Chainsaw that won’t Stay Running: Use Fresh gas

Fuel that sits in the tank for more than a month can start producing a gummy residue that can clog the carburetor and fuel lines. I recommend not storing gas for more than a month without adding a fuel stabilizer. The best approach is to use fresh fuel each time you use your chainsaw. This will not only guarantee the best performance from your saw but also increase its service life.

Why does my chainsaw dies when I give it gas

If your chainsaw dies or cuts out when you give gas or at full throttle. It is most likely because the engine is not receiving the required fuel and air to keep it running.  To fix the issue, check and clean the air filter and the spark plug. If that does not fix the issue, check and clean the carburetor and always use fresh gas.

Why Does My Chainsaw Start and then Stop?

When your chainsaw starts fine but then stops, the reason is often that the engine does not receive the correct fuel-air mixture. The most common reasons for this are a blockage in fuel lines, a clogged or faulty carburetor, a dirty air filter, or a faulty spark plug.

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