When you press the throttle trigger to run your chainsaw at high speed, you notice it’s no longer giving you the power you expect.
A Craftsman chainsaw loses power when the engine doesn’t receive the air, fuel, and spark required for combustion.
This can be a result of a dirty spark plug, plugged air filter, clogged spark arrestor, plugged fuel filter, clogged fuel lines, or a dirty carburetor. Your carburetor may also need an adjustment.
Follow the safety precautions before performing repairs including removing the spark plug wire and waiting for all moving parts to stop.
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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.
This is Why Your Craftsman Chainsaw Loses Power
1. Plugged Air Filter
The air filter is a required maintenance part used to protect the engine from contamination. It is designed to seal the air intake to keep dirt and debris out.
Working with your chainsaw creates dirty conditions. When the filter isn’t cleaned regularly, the buildup of dirt and sawdust can clog the filter keeping sufficient airflow from getting to the engine.
When you experience this, check the filter. Clean it or replace it if necessary. Never run your chainsaw without an air filter. Doing this can result in significant engine damage.
Here are cleaning instructions for a couple of types of filters used on Craftsman chainsaws. If you have a different style or are unsure of the cleaning instructions, consult your owner’s manual.
Clean a Craftsman chainsaw FLEECE air filter:
- Close the choke to keep dirt from falling into the carburetor choke when cleaning the air filter housing and removing the filter.
- Remove the air filter cover.
- Clean around the air filter to remove any dirt and sawdust.
- Remove the air filter.
- Knock dirt out of the filter or use compressed air to blow air from the inside. DO NOT use a brush.
- If the filter is very dirty, wash it in a mild dish detergent and water solution, and rinse from the inside outward until the water runs clear.
- Allow the filter to completely air dry. DO NOT use heat on the filter as this can damage it. DO NOT apply oil to the filter.
- Reinstall the clean filter.
- Purchase and install a new air filter if the old filter is extremely dirty or damaged
- Reattach the cover.
Clean a Craftsman chainsaw FOAM air filter:
- Close the choke to keep dirt from falling into the carburetor choke when cleaning the air filter housing and removing the filter.
- Remove the air filter cover.
- Clean around the air filter to remove any dirt and sawdust.
- Remove the air filter.
- Inspect it for damage. If it is brittle, torn, or damaged in any way it’s time to replace it with a new one.
- Wash it in a mild dish detergent and water solution. Rinse the filter and squeeze to remove excess water.
- Allow the filter to completely air dry.
- Once dry, apply clean engine oil. 2-cycle engine oil or SAE30 engine oil works well.
- Reinstall the clean filter.
- Reattach the cover.
2. Clogged Spark Arrestor
A spark arrestor screen is installed on most Craftsman chainsaws as a safety component. You will find the screen attached to the muffler to prevent hot exhaust material from shooting out of the muffler.
When the screen becomes plugged with carbon buildup, you may experience a loss of power where the Craftsman chainsaw won’t run at full RPMs. This is because the engine isn’t able to exhaust sufficiently.
This screen should be checked often and cleaned to prevent buildup. To do this, first, disconnect the spark plug wire and allow the muffler to cool.
Carefully remove the spark arrestor screen. Clean it using a metal brush. If you find any damage or holes in the screen, replace it with a new spark arrestor screen.
Reattach the engine exhaust cover and engine cover once you have installed a new or clean spark arrestor. Reattach the spark plug wire if you are done performing all repairs and maintenance.
3. Old Fuel
Your Craftsman will begin losing power when the engine isn’t getting sufficient fuel. This can be due to fuel restrictions caused by a plugged fuel filter, plugged fuel line, or dirty carburetor.
The carburetor may only need an adjustment to fix the amount of fuel mixed with air.
Begin by checking the fuel supply to ensure it is fresh. If it is old, fill it with fresh fuel. You can find more information on fuel to use in your Craftsman chainsaw here.
4. Clogged Fuel Filter
A small cylinder-shaped component is attached to the fuel line to keep dirt and debris from getting into the fuel system. This fuel filter can be found inside the fuel tank.
When the fuel filter is not changed out regularly or you are using very dirty fuel, it can become plugged keeping a sufficient amount of fuel from flowing through the filter.
This lack of fuel flow will cause a Craftsman chainsaw to lose power. Replace a plugged air filter with a new one.
5. Clogged or Punctured Fuel Line
Old fuel sitting in the chainsaw is likely to leave behind varnish and sticky deposits that clog the fuel line. This can restrict fuel flow.
When you find there is a clog in the fuel line, remove the fuel line and clean it to remove the clog using carburetor cleaner. Spray the carburetor cleaner into the line to loosen the clog. Then blow compressed air through it to remove the clog.
Repeat spraying the cleaner and blowing compressed air until the line is free of the blockage. Replace with a new line when you find it is dry or cracked.
Another thing to look for is a punctured fuel line. A punctured line can introduce air into the fuel system. Additional air to the cylinder can make your Craftsman lose power when there is no longer a correct mixture of fuel and air.
6. Dirty Carburetor
The carburetor mixes the correct proportion of air and fuel required for your Craftsman chainsaw to start and continue to run.
The passageways can become clogged and the small components can fail to function correctly which can be the reason the chainsaw stops running.
Old fuel is a big reason why a Craftsman carburetor will stop working. You may be able to clean or rebuild your carburetor to get it working again. You will have to replace the carburetor if this doesn’t work.
7. Carburetor Needs Adjustment
The carburetor may need to be adjusted to change the RPMs at idle speed and at full throttle. There are adjustment screws on the carburetor to make these adjustments.
The screws are labeled “L” for low speed and “H” for high speed. Let the chainsaw idle and adjust the “L” low-speed screw clockwise and counter-clockwise until you find the “sweet spot” where it runs smoothly and not sluggish.
Next, adjust the “H” high-speed to get a good smooth RPM at full throttle. Don’t over-adjust and allow the RPMs to increase too much or you will damage the engine.
Craftsman does have some limits to the adjustments you can perform to the carburetor.
If you are having problems with the carburetor and are unable to adjust the carburetor or are unsure how to safely perform the adjustments, bring your chainsaw to your local Craftsman dealer.
A special tool may be required to keep owners from making adjustments to their carburetors.
8. Dirty Spark Plug
Spark is required to ignite the fuel and air mixture to form combustion in the cylinder so the chainsaw will continue to run. When the Craftsman chainsaw isn’t getting consistent spark, it will bog down and lose power.
The spark plug is a maintenance part. It must be replaced regularly. I recommend replacing it once a year for casual usage.
However, if you are using your chainsaw often, you may need to change it quarterly to ensure you are running a good plug.
The spark plug will become dirty over time causing an intermittent spark and a loss of power. Remove the spark plug and inspect the tip. If it is dirty, but not very dark in color, you can try to clean it using a wire brush.
If you find the spark plug is very dark in color; has broken porcelain or burnt electrode, you must replace it with a new one.
Before installing a new spark plug, check that the spark plug gap is correct. Install the plug and securely attach the spark plug wire. An incorrect gap or a loose wire can cause the chainsaw to bog down and lose power.
9. Chain Brake is Engaged
The chain brake is a plastic handle that sits in front of the regular handle you use to hold the chainsaw. This is a safety feature installed to protect the user when the saw kicks back.
When the chain brake is engaged, the chainsaw will bog down losing power. Check the chain brake and make sure it is in the off position.