Chainsaw Cuts Out When Throttle is Applied: Tip from a pro


It’s a busy day ahead of you when you know that piles of lumber need to be sawed down. Luckily, your go-to chainsaw with its all-powerful gasoline engine is there to make things easy for you. However, as you push the throttle all the way down to get the maximum cutting speed, the engine begins to lose power. Knowing that it will be tedious to see woods at this cutting speed, you wonder if there’s a way to fix it. If that’s the case, then this article might have all the answers you need.

Chainsaw cuts out when the throttle is applied, what to do:

  • Clogged fuel filter: Examine the fuel filter and check for any deposits.
  • Cracked fuel lines: Access the fuel lines to see if they are tight and free of any leakage/
  • Dusty air filter: Make sure the air filter is cleaned from dirt.
  • Clogged carburetor: Analyze the carburetor and its components and perform cleaning where necessary.
  • Clogged muffler: Check the muffler for any carbon deposits.

As the throttle is pressed, the engine begins to draw more fuel from the carburetor to maximize its rotational speed. However, if, due to any reason, the engine doesn’t receive an adequate amount of fuel, it begins to draw more air, due to which the mixture becomes lean. As a result, the lean mixture cannot deliver enough power to the engine at wide-open throttle (WOT). This implies that there is bound to be some restriction, either in the carburetor or in the fuel lines. This makes your engine gets a lean mix and hence, stalls. To fix this issue, we shall troubleshoot the components involved in the fuel delivery system one by one.

Scroll on to read in detail about the causes mentioned above.

Causes and Fixes of a Stalling Chainsaw at Full Throttle:

There may be one of these various reasons that are causing your saw to stall at wide-open throttle (WOT). It would be best if you began the troubleshooting by investigating these causes one by one.

1. Clogged Fuel Filter:

Fuel filters are situated at the fuel line’s inlet that carries the gasoline from the tank to the carburetor. Deposits accumulate on the gasoline filter located within the fuel tank as a result of poor gasoline quality. As the name implies, it filters the fuel so that the carburetor receives a clean and uncontaminated gasoline charge. However, when it becomes blocked, the flow of fuel to the engine is disrupted, causing the engine to stall.

Expert Opinion: Based on my experience working at multiple chainsaw forums and addressing various chainsaw-related issues, I recommend you begin the inspection from the fuel filter first, as it is the leading cause for a stalling engine. Apart from getting clogged, the filter might also come off the fuel line. As a result, the carburetor will not draw enough gas when there is a high demand for gasoline at WOT, causing the engine to stall. Hence, you need to open the fuel tank and see if the filter isn’t lying there while being dislodged from the fuel line.

– Repair: Fuel Filter Inspection and Replacement:

To inspect the fuel filter, remove the chainsaw’s fuel cap and pour some gasoline into a different container. Then, using a dental pick or a thin metal rod, filter the tank. Examine the filter’s quality. If It appears clogged, you should buy a new filter and replace the old one. If it seems clean, leave it as it is and consider checking the fuel lines, carburetor, and air filter for restrictions.

2. Fuel Lines:

Any slight restriction or debris in the fuel lines can suffocate the engine from gasoline at peak demand for fuel, thus causing it to stall. The fuel line might get clogged due to stale fuel deposits. Or it might have become cracked.

Expert Opinion: When the fuel line has become cracked, it will leak gasoline and draw air from outside into the fuel line. At WOT, a vacuum is formed in the fuel lines, which inhibits the flow of gasoline to the engine. Therefore, the fuel lines need to be tight at their connections to eliminate any chances of vacuum formation.

– Repair: Inspect the Fuel Lines:

If you notice that the line is leaking fuel, you should know that replacing it is the only way to go. However, if you see that the stall persists after you’ve troubleshot other methods, then try examining your line at its connection to the tank and see if it’s tight enough or not. In case it is, please proceed to the next step.

3. Dusty Air Filter:

You should examine the air filter before checking the carburetor as it is easier to do so. As a fuel filter, an air filter filters out the dust contaminants present in the air before going into the carburetor. However, when the filter gets plugged with dirt and dust, it filters too much air, thus depriving the engine of adequate air that is necessary for combustion. Hence, the engine is likely to stall.

Expert Opinion: A dusty air filter might be the most common issue when the engine is stalling in general and not at WOT. It is because if the filter had been clogged, your engine would not start at first, or if it does start, it will continue to stall even at lower RPMs. Our problem is the engine stall at higher RPMS (or WOT), the most common causes of which include the fuel filter and carburetor. Nevertheless, cleaning the air filter has solved the issue for most individuals, and that’s why you should consider doing so as it’s not a difficult task and cleaning it ensures that the engine runs smoothly.

– Fix: Cleaning the Air Filter:

Your chainsaw’s air filter screen is located at the rear. First, loosen the fasteners that hold the air filter in place with a screwdriver. Next, remove the filter and inspect it for dirt/deposits. If the dirt buildup isn’t too significant, a soap and water solution shall suffice. However, if it still does not appear to be in good condition after cleaning, consider replacing it entirely. Air filters are relatively inexpensive, and you should replace them once a year to reduce engine problems.

4. Clogged Carburetor:

If fixing the filters hasn’t solved the problem, then you’re probably looking at a clogged carburetor. A carburetor mixes the air and gasoline and supplies the mixture to the engine for combustion. Unfortunately, fuel stored for longer durations in the tank is bound to degrade in its quality. As a result, it forms white, sticky deposits that clog the fuel jets of a carburetor and ultimately affect the amount of fuel going to the engine. Hence, the carburetor needs to be serviced to ensure normal functioning of the carburetor.

Expert Opinion: To confirm that the engine stall at WOT is due to a carburetor, I advise you to bypass the current fuel line and create an alternative line that pumps fuel from a separate bottle into the carburetor. If the engine still stalls at WOT, the carburetor needs to be appropriately checked and serviced. Also, during this operation, most users experience bubbles being formed in the fuel line at WOT. These bubbles further confirm that the engine cannot draw sufficient fuel at peak demand, and thus it stalls. The stall should subside as soon as the throttle is lowered.

To ensure that you remain on the right track, pay special attention to the needle while cleaning the carburetor, as this is responsible for drawing fuel from the fuel lines. If the needle gets stuck, the carburetor won’t draw enough fuel. Multiple users have reported this issue as the primary cause behind engine stalling.

– Fix: Carburetor Cleaning:

Because small engines, such as those found in chainsaws, have fewer mechanical parts, carburetor cleaning is significantly easier. You only need a standard carburetor cleaning spray. The following are the steps:

Step 1: Identify the carburetor:

To begin, find the carburetor of your chainsaw. It is usually found behind the air filter. So, if you removed the air filter before, you should have easy access to the carburetor.

Depending on your ability level when performing DIY work, you can consider removing and cleaning it or cleaning it without completely detaching it from the chainsaw. Nonetheless, we do not recommend thoroughly detaching it as it makes the job a little complex.

Step 2: Detach and clean the bowl:

First, remove the bowl nut from the carburetor and remove the bowl. Most of the time, the bowl contains expired gasoline and its deposits. As a result, it should be cleansed of any residues and old gasoline.

Step 3: Spray the carb cleaner on the interior:

Next, spray some carburetor cleaner liquid over the carburetor’s inner portions. Don’t forget to clean the bowl nut, which is a jet and is more prone to becoming clogged. When you observe spray pouring out of the other side of a jet, it means that any debris has been removed.

After you’ve finished cleaning, reassemble everything that was removed.

5. Clogged Muffler:

If the engine stall persists after you’ve troubleshot each of the above components, another component that contributes to this problem occasionally is the muffler. The muffler contains the spark arrestor screen and the exhaust port. The carbon buildup from the fuel can often clog the spark arrestor screen or the exhaust port. It might be another reason behind the engine shutting down at full throttle.

Expert Opinion: Most users tend to ignore the muffler and the spark arrestor while encountering such a problem. If you delve deep, the main reason excessive carbon buildup occurs at the exhaust is when your engine runs rich. (Primarily, this is when you run the engine at full throttle; at higher RPMs, the air-fuel mixture becomes rich or high in gasoline). Richer mixtures produce a higher value of carbon content at the exhaust. Meaning that carbon deposition is maximized at WOT. Hence, this is precisely why the exhaust gases cannot escape at full throttle, causing the chainsaw to cut out as a result.

– Repair: Clean the exhaust port and spark arrestor screen:

To clean the spark arrestor screen, remove it and use a propane torch (if available) to dislodge any carbon deposits. Instead of a torch, you can also use a wire brush to clean the arrestor screen. Also, use the same wire brush to see if the exhaust port can be cleaned from the soot deposits. After cleaning, fix everything back and check if the problem is solved.

Final Remarks

To summarize, we can see that the engine stall or shutdown-related problems arise due to hitches in the fuel supply system or ignition system. Hence, through occasional maintenance such as regular cleaning, servicing components, and fresh fuel addition, you minimize such occurrences.

This article’s goal was to make you aware of the basic troubleshooting steps that need to be performed in case you encounter a problem with your chainsaw. It is an excellent practice to try to fix your tools independently. If, however, the problem persists, consider consulting a professional.

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