Chainsaw Overheating. A professional’s perspective


The engine in a chainsaw runs at high speed to give the chain its cutting power. The high rounds per minute (RPM) means that it is easy to overheat the engine. A chainsaw overheating is not uncommon, especially in the summer.

Chainsaw Overheating

Common reasons behind chainsaw overheating are a wrong oil/fuel mixture, a blocked or clogged exhaust. It is also possible that the air filter is clogged. Or you are using a dull chain. If you are using your chainsaw for an extended time, or it is not powerful enough for the job, it can also overheat.

I will first look at the symptoms of an overheated chainsaw. Before looking in more detail at the various reasons why. And how to prevent it.

Symptoms of an Overheated Chainsaw

You can tell by the following symptoms that a chainsaw is overheating:

  • Temperature: The chainsaw feels much hotter than usual.
  • Sound: The chainsaw produces a different sound, usually a lower note.
  • Performance Loss: A sudden or gradual drop in performance.
  • Smoke: The chainsaw produces too much smoke that is of a different color than the usual exhaust smoke.

Reasons Behind Your Chainsaw Overheating

There are multiple reasons why your chainsaw is overheating. The most common are:

  • Insufficient oil proportion in the oil-fuel mixture: Your chainsaw’s 2-stroke engine uses a mix of oil and fuel. If the oil proportion in the mixture is too low, your chainsaw will overheat.
  • Blocked/clogged exhaust port: A clogged exhaust port traps hot fumes coming from the engine, causing your chainsaw to overheat.
  • Clogged air filter: A clogged air filter reduces the engine’s ventilation which can cause your chainsaw to overheat.
  • The chain is dull/not sharp enough: A chain that isn’t sharp enough requires more power to do the same job. This can overload the engine and causing the chainsaw to overheat.
  • Too much load/cutting a tree that is too big for your saw: Overworking the motor causes the chainsaw to overheat.

Let’s look at them in more detail:

● Insufficient Oil Proportion in the Oil-Fuel Mixture

This may be the most common cause of your chainsaw overheating. Most chainsaws use 2-stroke engines, except electric chainsaws. These 2-stroke engines work on a mix of oil and fuel. Oil is mixed into the engine’s fuel to function as a lubricant for the pistons moving inside the engine. Suppose the mixture doesn’t have an adequate proportion of oil. In that case, the pistons start grinding against the engine’s inside walls. Generating a lot of heat that heats the engine itself and can cause serious damages.

New chainsaw users usually face this problem when they do not know enough about chainsaws or 2-stroke engines in general. However, even chainsaw veterans face this problem because they sometimes use the wrong fuel mix by accident. In any case, this is most probably the quickest way to overheat and destroy a chainsaw, as it shows its impact within 10-12 minutes of starting it up. What’s worse is that users usually can’t even detect that something is wrong, until their chainsaws stop working.

● Blocked/Clogged Exhaust Port

Like a car, a chainsaw has an exhaust port. Hot fumes generated as a by-product of combustion exit the engine there. The exhaust port usually doesn’t require much attention, but it can cause some serious problems if it becomes clogged. This is because a clogged exhaust port won’t let hot fumes escape. Trapping the heat inside the engine. The engine will become hotter than usual when this happens.

Fortunately, a chainsaw’s exhaust port rarely becomes clogged. It usually happens when the chainsaw is stored in a dirty place, where it is exposed to a lot of dust and debris. A clogged exhaust port is quite easy to notice if you regularly use your chainsaw because it sounds different than usual.

● Clogged Air Filter

Unlike a clogged exhaust port, a clogged air filter is more likely to happen. The engine needs air for combustion and engine ventilation. To prevent fresh air from carrying dust into the engine, chainsaws have an air filter installed at the air intake. A lot of air passes through this filter when the engine is on, and over time it will collect a lot of dust and debris. The air filter will eventually get to a point where it will become so clogged that it won’t let fresh air pass through.

At this point, the engine will stop working because it cannot run without air. This will make the chainsaw overheat due to the lack of cooling fresh air. A clogged air filter is especially common for a chainsaw that is used in the rain or shortly after. Because moisture that gets trapped in the air filter catches more dirt particles than when the filter is dry. Therefore, you must always clean the air filter after using your chainsaw in the rain.

Checking and cleaning the air filter is part of regular maintenance. I recommend checking it often. Sawdust is prone to clog it. If your machine has a foam air filter, you can wish it with some hot water. If it uses a paper air filter, you have to replace it. If the foam filter is damaged, you need to replace it as well.

● The Chain is Dull/Not Sharp Enough

A chainsaw whose chain isn’t sharp enough requires a lot more power than it normally. Since more force will be required for the same job, the motor will have to deliver more power. And heat up. Overheating from a dull chain usually isn’t enough to cause serious damage to the chainsaw on its own. Still, it can be problematic if it’s in combination with other issues, such as a clogged air filter.

Fortunately, a dull chain is quite easy to notice because it:

  • produces a lot of wood dust when cutting,
  • requires a lot more pressure than usual,
  • produces smoke even when oiled properly,
  • and makes uneven cuts.

● Too Much Load/Cutting a Tree Which is Too Big

Chainsaw operators sometimes try to cut down trees that are too big for their saws. This causes the guide bar to get stuck in the tree while the engine continues running, attempting to somehow force the bar out of the tree.

Doing this can seriously damage your chainsaw, and it’s simply poor practice. Trying to rotate the chain while a large piece of wood is locking it in place isn’t a great idea because it can cause the guide bar to bend and the engine to overheat. Therefore, you shouldn’t try to release the guide bar with engine force when it gets stuck. Instead, make use of a felling wedge to get it out. 

How to Prevent Your Chainsaw from Overheating

Routine maintenance of a chainsaw is usually enough to prevent it from overheating and other problems. Overheating can be easily avoided. Here are some ways to prevent your chainsaw from overheating:

  • Using the correct oil-fuel ratio: Make sure that your chainsaw always has the correct oil-fuel ratio.
  • Regularly clean the exhaust port: Ensure that your chainsaw’s exhaust port is always clean and clear of obstructions.
  • Regularly clean the air filter: Ensure that your chainsaw’s air filter is always clean so that the engine continues getting the necessary supply of fresh air.
  • Regularly sharpen the chain: Regularly check the chain and sharpen it when needed.
  • Avoid overloading your chainsaw: Avoid forcing your chainsaw to over-perform, for example, forcing it to cut a too-big tree.

Let’s look at the ways to prevent your chainsaw in more detail:

● Use the Correct Oil-Fuel Ratio

Ensure that you use the correct oil fuel mixture in your chainsaw. Most chainsaws work best on the 1:50 oil-fuel ratio. For the correct information, consult your chainsaw’s user manual. Users that don’t use their chainsaws regularly may buy pre-mixed fuel for their saws.

● Clean the Exhaust Port Regularly

As said before, a chainsaw’s exhaust port rarely gets clogged unless it’s stored in a dirty place. Just to be safe, check the exhaust port regularly and clean when necessary.

● Clean the Air Filter Regularly

Unlike the exhaust port, the air filter requires regular cleaning. Cleaning the filter is quite easy, although it’s well protected and not exposed to the surface. The best way to know the air filter’s location is from the slits at your saw’s surface that is there to ensure a free airflow in and out of the chainsaw. In extreme cases of debris buildup, the slits may become covered from the inside by particulate matter, which is dangerous to your chainsaw’s longevity.

Once you know the air filter’s location, remove its outer covering using a screwdriver. Then remove the main filter cover present under the outer covering. This will give you access to the air filter. Make sure to remove the filter from your chainsaw gently.

To clean a foam air filter, you’ll need two buckets of water and a hand bristle brush. Alternatively, a toothbrush could do the job. Put some soap in a bucket filled with hot water and mix it to create foam. Take the filter, gently scrub it with the brush to loosen the dirt particles, then dip it in the hot water bucket. Swirl it in the water to let the soap absorb into the filter and pull out the dirt. After some minutes in the hot water bucket, remove it and dip it in a cold water bucket to remove the dirt particles not taken out by the hot water. Then give it enough time to dry completely.

You should also clean the covers. To clean the covers, dip them one by one in the hot water bucket, scrub them gently with the brush, then rinse with cold water. Leave them for some time to dry. Once the filter and covers have dried completely, reinstall them in their correct positions. Start with the filter, then the inner cover, and then the outer cover, locking each in place using a screwdriver.

If you notice that the foam air filter is damaged, you need to replace it. If your machine uses a paper air filter, it can not be cleaned. When dirty, it needs to be replaced.

● Regularly Sharpen the Chain

It’s good practice to check the chain every time you use your chainsaw. Sharpening a dull chain is quite a simple procedure that’ll take you 10-15 minutes. It requires inexpensive tools like files and file guides.

● Don’t Cut Trees Too Big for Your Chainsaw

Never cut trees too big for your chainsaw as it can cause overheating and other serious issues. If your saw’s guide bar gets stuck in a piece of wood, use a wedge to get it out instead of using the engine’s force.

Can You Fix an Overheating Chainsaw?

The answer to this question mostly depends on the amount of damage your chainsaw has suffered because of overheating. If the chainsaw no longer starts, it’s most likely because the piston has been damaged. You can try to replace the entire engine block, but it usually costs more than a new chainsaw. An overheated chainsaw, once fixed, can generally work fine enough without any serious loss of performance.

Chainsaw’s Blade Overheating:

It’s common for a chainsaw blade to heat up when cutting, but it shouldn’t overheat or produce smoke. If you notice smoke and overheating, stop using your chainsaw immediately. A chainsaw’s blade overheating is usually caused due to the following reasons:

  • Improper/insufficient lubrication.
  • A dull chain.
  • A mismatch between the chain drive and the groove blade.
  • Very tight chain tension.

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