Chainsaw Keeps Cutting Out – Solved

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If your chainsaw suddenly cuts out, there are a number of possible reasons. As you might expect this has something to do with the engine, but finding the cause is easy. The even better news is you can fix most of these problems without taking the chainsaw to a repair center.

A chainsaw keeps cutting out because the air to fuel mix ratio is incorrect. To resolve this problem, add new fuel and check the fuel line. Check the carburetor, air filter and spark plug and clean or replace them if necessary.

How to Repair a Chainsaw That Won’t Stay Running

The first thing you have to do is narrow down the possible causes. The most likely are the fuel, carburetor, fuel filter, air filter and spark plug. The term cutting out means the chainsaw starts but stalls.

This happens because the engine is not getting sufficient fuel or the air to fuel mix is incorrect. If the mixture is wrong, the fuel will be either too rich or too lean. The Poulan Pro 20 in. 50cc is a powerful chainsaw, but it needs enough fuel to run.

The fuel is one of the components you have to look at along with the carburetor, but it does not end there. The problem could have affected the spark plug, air filter and other components. If you are going to check the engine, might as well inspect the other parts that might need cleaning or replacement.

An even more important reason is that these components work together. The air and fuel filters ensure the fuel gets to the carburetor cleanly. The carburetor mixes the air and fuel and the spark plug literally provides the spark to ignite the fuel and start the engine. If one of these is not working, the chainsaw will not stay running.

Add New Fuel

Chainsaw gas should be replaced every 30 days. If fuel sits longer than four weeks, it turns into a thick sludge and can clog the engine. Add a fuel stabilizer if you have to keep the fuel there for long periods. If you are going to store the chainsaw for the winter, empty the tank or put antifreeze.

Make sure the fuel mix ratio is correct. Most brands recommend a 50:1 gas and oil mix. Other chainsaws might need 40:1 or 32:1 so check your manual for details. Remember to replace the fuel after 30 days to avoid problems.

If your chainsaw dies after receiving new fuel, the spark plug might be dirty or damaged. It could also be due to the fuel filter, air filter or carburetor. The following will help you sort it out.

Clean or Replace the Spark Plug

If your chainsaw will not stay running, the spark plug is a good place to start looking. A spark plug can get damaged from wear and tear. Other causes are oil, oil residue or carbon buildup. If this occurs, the voltage grounds out instead of sparking. Problems with the spark plug can also be the reason why chainsaws do not spark.

Solution. Turn the chainsaw off. Remove the spark plug wire and the plug itself. Replace it if there is damage. If it just looks dirty, clean it with a wire brush. If there is oil residue, check the rest of the engine for possible oil leaks. You will need a new sparkplug if you find yourself having to clean it often.

Clean or Replace the Air Filter

The air filter prevents sawdust and other particles from entering the chainsaw. Through constant use however, the filter gets clogged with debris and prevents air from passing through. The clogged dirt blocks the vents and increases the temperature inside the engine.

Solution. Clean or replace the air filter regularly. Check your owner’s manual for the suggested frequency. Depending on the situation, cleaning or replacement may be needed. Look for an air filter that works with your chainsaw make and model. Anzac for example, manufacturers air filters for various Husqvarna chainsaws.

How to clean a chainsaw air filter.

  1. Remove the air filter cover. The location varies depending on the chainsaw so refer to your owner’s manual. Once you find the cover, use a screwdriver to loosen the screws.
  2. You will see the air filter inside. It is usually made of foam. Remove the filter. Pour some water in a bucket and add a few drops of liquid soap. Wash the foam filter in this soapy mix. Use a toothbrush to remove stubborn dirt.
  3. Squeeze the foam gently when you are done. Let the foam dry and put it back into its original location. Put the cover back, reattach the screws and you are done.

If the foam filter is damaged, you have to replace it. Otherwise, cleaning will be enough. If your chainsaw uses a paper filter it has to be replaced. Those cannot be cleaned and reused.

Clean the Carburetor

Like the rest of the engine, the carburetor gets clogged with dirt. If it not adjust properly, it will produce the wrong fuel mixture as well. By cleaning the carburetor, you will reduce the chances of engine cut out significantly.

How to clean a chainsaw carburetor

  1. Turn off the chainsaw. Remove the screws on the carburetor casing. Its location might be different in yours, consult your manual.
  2. Use a carburetor cleaner to remove gummy oil and dirt.
  3. With the same cleaning solution, remove dirt, grime and oil on the needle valve. Use a metal brush when needed to get rid of stubborn dirt.
  4. Once the needle valves have dried, add a bit of the carburetor cleanser in the fuel tank. With the chainsaw still off, pull the starter rope a few times. This forces any remaining residue into the carburetor. Clean it off.
  5. After you are done, empty the fuel tank. Wipe any oil sludge there. Pour new fuel, following the suggested mix ratio. Turn the chainsaw and let it run for a few minutes. You will see it no longer cuts out.

Adjust the Carburetor

Sometimes the problem is the carburetor, but in many cases a bit of adjusting is all that is needed. Adjusting is easy though.

There are three adjustment screws on a chainsaw:

  • Throttle / idle speed: determines how long the throttle valve remains open after letting go of the throttle trigger.
  • High speed fuel (labeled H): if set too low, cutting power is reduced. This can also damage the cylinder and other components. If it too high, the RPM needed for optimum performance will not be attained.
  • Low speed fuel (labeled L): controls the air and fuel mix. If too low, the mixture gets too lean. If adjusted to too high, the mixture gets too rich.

How to adjust a chainsaw carburetor:

  1. Add new fuel.
  2. Wait for the chainsaw to warm up, then turn either the L or H speed adjustment screw. If you start with the L speed, rotate it once. Do the same with the H adjustment screw.
  3. Make adjustments incrementally, and each time check how the chainsaw responds. Even a slight adjustment can make a huge difference, so do not make several rotations.
  4. The recommended carburetor settings will depend on the chainsaw. This information will be on the owner’s manual so you should check it first.

Clean or Replace the Fuel Filter

The fuel filter keeps debris from getting to the fuel line. If your chainsaw keeps cutting out, the fuel filter is either damaged or covered in dirt. When either of that happens, fuel will not reach the engine. Whatever bit of fuel that does get through is dirty, which causes the engine to stall.

Solution. Replace the fuel filter if it is dirty or damaged. Unlike air filters, cleaning a fuel filter does not help much, and fixing it is difficult. It is more practical to replace the fuel filter with a new one.

Before you do so, check what type of fuel filter your chainsaw uses. The replacement must be an exact match. Chainsaws have different configurations so follow the manufacturer instructions on how to install a new fuel filter.