How to Check Compression on a Chainsaw with a Test?

Patrick McMann

Knowledge Based

Hey there lumberjacks and lumberjills! Are you ready to take your chainsaw game to the next level? Well, if you want to ensure your trusty chainsaw is running at its best, you will want to check its compression.

“But Man, what the heck is compression?” I hear you ask. Simply put, compression is the measure of how much pressure builds up in the engine when the piston moves up and down.

And why should you care?

Well, if your chainsaw’s compression is off, it can lead to all sorts of problems, like a loss of power, difficulty starting, or even engine damage.

So, today, we will show you how to perform a chainsaw compression test like a pro! Don’t worry, it’s easier than it sounds, and with our tips and tricks, you’ll be able to get accurate readings and interpret the results like a champ.

So, let’s rev up those engines and get started!

performing compression test on a chainsaw

How to Perform a Chainsaw Compression Test?

Now, let’s dive into how to perform a chainsaw compression test!


Before you start, you’ll need a few tools: a compression tester, a spark plug wrench, and a clean rag. You can find compression testers at most auto parts stores or online.

Ensure the chainsaw is turned off and the spark plug wire is disconnected to prevent accidental start-up. You should also remove any covers or components that may be in the way of accessing the spark plug.

Removing the Spark Plug

Next, use a spark plug wrench to remove the spark plug from the engine. Be careful not to damage the spark plug or the threads on the engine.

Testing the Compression

Once the spark plug is removed, attach the compression tester to the spark plug hole. Make sure the tester’s o-ring is seated correctly to prevent air from escaping.

Pull the starter rope several times to get an accurate reading on the compression gauge. Hold the throttle open to allow air to flow freely through the engine.

How to connect the Compression Tester to the Chainsaw?

To connect the compression tester to the chainsaw, simply thread the hose of the compression tester onto the spark plug hole. Make sure the tester is snugly connected to prevent air from escaping.

Compression Tested Alternative

If you don’t have a compression tester, you can still get a rough idea of your chainsaw’s compression using your thumb.

With the spark plug removed, cover the spark plug hole with your thumb and pull the starter rope.

You should feel resistance against your thumb as air is forced out of the engine.

This is a crude method, but it can give you a general idea of the compression.

Read More: How Hot Does a Chainsaw Muffler Get?

How to Get Accurate Readings?

First, ensure your chainsaw is working well before performing a compression test. Check the spark plug, fuel filter, and air filter, and replace or clean them if necessary.

You’ll also want to warm up the engine by running it for a few minutes to ensure more accurate readings.

How to Interpret the Results?

Alright, let’s talk about how to interpret the compression test results and what constitutes an ideal compression for your saw!

When you perform a compression test, you’ll get a reading in psi (pounds per square inch) indicating the engine’s pressure.

So what does that number mean?

Generally, a healthy chainsaw requires a compression reading of around 100-150 psi. However, keep in mind that the ideal compression can vary depending on the make and model of your saw, so it’s always a good idea to consult your owner’s manual for specific guidelines.

If your chainsaw’s compression reading falls below the ideal range, it could be a sign of engine wear or damage. You may notice decreased power, difficulty starting, or other issues.

However, don’t panic just yet – low compression doesn’t always mean your saw is on its last legs. It could be something as simple as a dirty air filter or a fouled spark plug.

On the other hand, if your chainsaw’s compression reading is significantly above the ideal range, it could be a sign that the engine is carbon-fouled or that the piston rings are worn. This can lead to engine damage over time, so it’s essential to address the issue as soon as possible.

Learn More: How Heavy are Chainsaws?

How to Fix an Unstable Chainsaw Compression?

Uh-oh, did your chainsaw’s compression test reveal an unstable reading? Don’t fret – there are a few things you can do to fix the issue and get your trusty saw back in top shape.

First, check the spark plug to ensure it’s in good condition and properly gapped. A faulty or worn spark plug can affect compression, so it’s essential to replace it if necessary.

Next, check the air filter to ensure it’s clean and debris-free. A dirty air filter can restrict airflow and cause low compression, so cleaning or replacing the filter can help improve compression.

If those steps don’t do the trick, it’s possible that the issue lies with the piston, cylinder, or valves. These components can wear out over time, leading to decreased compression. In this case, it’s best to consult a professional for a thorough diagnosis and necessary repairs or replacements.

Regular maintenance, such as keeping the air filter clean and changing the spark plug periodically, can go a long way in preventing unstable compression in the first place. So make sure to give your chainsaw the care it deserves to keep it running at its best!

What Affects Chainsaw Compression?

Several factors can impact chainsaw compression.

First up, we have worn or damaged piston rings. These little guys play a significant role in maintaining compression by keeping air from escaping the engine. You might notice decreased power or difficulty starting your saw if worn or damaged.

Another culprit of low compression is a scored or damaged cylinder wall. This can allow air to escape past the piston, leading to a loss of power and performance. And let’s be real, nobody wants a wimpy chainsaw!

A dirty or clogged air filter can also impact chainsaw compression by restricting airflow into the engine. This can cause the engine to work harder than it needs to, leading to decreased power and efficiency.

Finally, a leaking head gasket can allow air to escape from the combustion chamber, leading to low compression and poor performance. If you notice oil or coolant leaking from your chainsaw, it’s time to get it checked out.

By the way, the temperature can also affect chainsaw compression. Generally, compression will decrease as temperature increases because the air inside the engine expands, which decreases the pressure.

Conversely, compression will increase as temperature decreases because the air inside the engine contracts, which increases the pressure.


How do you do a compression test on a 2-stroke chainsaw?

Performing a compression test on a 2-stroke chainsaw involves several steps. First, ensure the chainsaw turns off, and the spark plug is removed.

Then, screw it into the spark plug hole using a compression gauge. Next, pull the starter rope several times, and take note of the highest reading on the compression gauge.

How many pulls do to check compression?

It’s generally recommended to pull the starter rope about 4-6 times, but you may need to do more pulls if the engine is not in good condition or has low compression.

For a compression test on a 2-stroke chainsaw, you would pull the starter rope several times until you get a stable reading on the compression gauge. The number of pulls required to obtain a stable reading can vary depending on the chainsaw model and its condition.

How do I know if my chainsaw has low compression?

If your gas chainsaw has low compression, it will exhibit signs such as difficulty starting or not starting at all, lack of power or reduced cutting performance, excessive smoke or exhaust fumes, and unusual engine noises.

Additionally, you may notice a decrease in fuel efficiency, which can result in increased fuel consumption and higher operating costs. You can also perform a gauge compression test to determine if your chainsaw has low compression.

What is standard chainsaw compression?

The standard compression reading for a chainsaw engine varies depending on the model and manufacturer. Most chainsaws generally have a compression reading between 100-150 psi (pounds per square inch) when the engine is in good condition.

Can you check compression by hand?

While it is true that some people use a thumb test to check compression on a chainsaw engine, it is not a reliable method, and it may not provide accurate results.

The thumb test involves placing your thumb over the spark plug hole while pulling the starter rope. If you feel a strong suction, it indicates that the engine has good compression.

Wrap Up! How to Check Compression on a Chainsaw?

And voila! There you have it!

So, grab your compression tester and spark plug wrench, and let’s keep your chainsaw in top shape and get to chopping like a pro!

Patrick McMann