How to Check Compression on a Chainsaw? – A Guide

how to check compression chainsaw

Compression is a key factor in determining the performance and life span of a chainsaw chain. A healthy engine should have adequate levels of compression, as this will increase the power output and fuel efficiency of your machine. Checking the compression on your chainsaw chain is a simple process that can be completed in just a few minutes. 

In this guide, we’ll show you how to check compression on your chainsaw so that you can keep it running at its peak performance. We’ll discuss what tools you need and how to measure correct levels of compression for different types of engines. 

With this knowledge, you’ll be able to keep your chain saw in top form and working optimally for years to come!  Let’s get started

How to Check Compression on a Chain saw

how to check compression chainsaw

To check the compression on a chainsaw, you will need a compression tester. First, remove the spark plug from the chainsaw and screw fuel tank the compression tester into the spark plug hole. Then, gently pull the chainsaw starter rope to turn the engine over. The compression tester will  chain brake measure the pressure inside the cylinder.

The ideal compression reading for a chainsaw is between 100 and 150 psi (pounds per square inch). If the compression reading is below chain brake 100 psi, it indicates that there may be a problem with the piston, cylinder, or piston rings. If the compression reading is above 150 psi, it indicates throttle that the engine may be running too hot or that there is carbon buildup in the cylinder.

It’s important to note that checking the compression on a chainsaws engine is just one part of diagnosing any issues with the chainsaws engine. Other throttle factors, such as fuel and air filters, spark plugs, and carburetor adjustments, can also affect the performance of the chainsaw. If you’re unsure about how to check the compression on your chainsaw or how to diagnose any issues, it’s recommended to consult a professional.

Why do we do a Chainsaw Compression Test?

The Chainsaw Compression Test is one of the most important tests that can be done on a chainsaw. This test measures the amount of compression in the piston and cylinder of a chainsaw engine, which helps determine if the engine is running correctly. It also helps to identify any wear or tear on the engine parts, so repairs can be made if necessary. 

The test is done by using a compression gauge to measure the engine’s piston and cylinder pressure, which can then be compared to the manufacturer’s specifications. 

This will help detect any problems that may be present in the chainsaw’s components, allowing for repairs or adjustments to be made before further damage is done.

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 Performing the Chainsaw Compression Test is essential for ensuring that your chainsaw is working at its best and will help you maintain it for years to come.

The test itself should only take a few minutes, so it’s worth taking the time to check up on your engine periodically.

What Affects Chainsaw Compression?

Chainsaw compression is a key factor in the performance of your chainsaw. It affects how much power and torque it will produce, as well as how efficiently it operates. The compression of a chainsaw is determined by several factors including the quality and size of the piston, cylinder, spark plug gap, fuel mix, air filter condition, and exhaust system condition.

The piston is responsible for compressing the fuel-air mixture that powers the engine. A larger piston allows for more compression but also requires more energy to turn over. Quality pistons are usually made from alloy aluminum or steel with an anti-friction coating to reduce drag on the walls of the cylinder.

The cylinder size determines how much fuel can be compressed into the cylinder and, therefore, how much power the engine can produce. A larger cylinder will allow for more compression but is heavier than a smaller one. If you are looking to maximize performance, make sure your chainsaw has a large enough cylinder.

The spark plug gap is the distance between the spark plug tip and the piston when they are at top dead center (TDC). This gap needs to be precise in order for your chainsaw to run correctly. An incorrect gap can cause misfires or poor combustion which will reduce performance.

The fuel mix is also important in terms of performance as it determines how much air-fuel mixture gets delivered to the engine. You should always use a premixed fuel that is designed for your specific chainsaw. The air filter should also be kept clean to ensure that the engine gets plenty of air and can breathe efficiently. If the filter gets clogged, it will reduce performance and can even cause engine damage.

Finally, the exhaust system should be checked regularly to make sure there are no blockages or restrictions that will reduce compression and performance.

How to Perform a Chainsaw Compression Test?

A chainsaw compression test is an important step in ensuring proper operation and maintenance of a chainsaw. It helps to identify problems with the engine such as low compression, which can lead to decreased performance or even engine failure. The compression test is easy to perform and only requires access to a few tools and some basic knowledge of how an engine works.

Tools Needed

To perform a chainsaw compression test, you will need a spark plug socket, suitable replacement spark plugs (if needed), a tachometer or rpm meter, and a vacuum pump gauge, as well as any other necessary tools for removing the cylinder cover on your machine model.


Start by disconnecting the spark plug lead and removing the spark plug from the cylinder head. Install the vacuum pump gauge in place of the spark plug, and connect it to the tachometer or rpm meter. Re-connect the spark plug lead for electrical power, but make sure to keep your fingers away from any metal parts that could cause a shock.


Once all connections have been made, run through one full cycle of starting and stopping your engine, while monitoring both gauges throughout each start-up. The pressure should remain steady during each start-up as long as there are no major problems with compression. If you notice any significant drops or spikes in either gauge reading then it may be time for further investigation.

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A chainsaw compression test is an important part of ensuring your chainsaw runs smoothly and efficiently. By performing a regular check, you can identify any potential problems before they become major issues and keep your machine in tip-top shape for many years to come. If you notice any errors or irregularities during the test then it may be time to consult a qualified mechanic for further diagnosis and repairs.

What to do If you do not have a Compression Tester?

If you do not have a compression tester, there are still several tests that can be done to determine if an engine is operating properly. One of the most common methods is a vacuum or pressure test. 

This type of test can be used for both gas and diesel engines and requires the use of a special gauge, which can be purchased at most auto parts stores. The gauge will measure the amount of space between two points in the cylinder head, indicating whether or not there is enough pressure or vacuum present for proper combustion.

Another option is to perform a “sniffer” test by attaching a hose to the spark plug hole and using an exhaust analyzer to detect any unburnt fuel in the exhaust system. This method can detect very small amounts of unburnt fuel that are often indicative of a lack of compression. Finally, if you don’t have access to any specialised tools, an experienced mechanic may be able to perform a simple test by manually measuring the compression in each cylinder with a feeler gauge.

How to Interpret the Results | What is an Ideal Compression for a Chainsaw?

Interpreting the results of a chainsaw compression test can be tricky. A good compression reading should be between 5 and 7 psi (pounds per square inch). However, this is just a general guideline because there are many factors that affect the ideal compression for a chainsaw, such as weather conditions, the age of the chainsaw, and the type of fuel used.

In order to accurately interpret your results, you should first determine what type of engine your chainsaw has. The two most common types are 2-stroke and 4-stroke engines. If you have a 2-stroke engine it’s usually best to aim for a higher compression reading than with a 4-stroke engine. A 2-stroke engine needs more pressure to push the fuel and air mixture through the engine.

Next, you should check your chainsaw’s owner’s manual for recommended compression readings. This will give you a better idea of what is considered an ideal reading for your particular model. It might also provide more information about how to adjust the chainsaw if it is not meeting these specifications.

Finally, take note of any changes in the weather or atmospheric conditions that could affect the results of your test. For example, high temperatures can reduce compression, while low temperatures may increase it. You should also consider whether you are using fresh fuel when testing your chainsaw as this can significantly influence the results as well.

How to Fix an Unstable Chainsaw Compression?

Chainsaw compression refers to the pressure (or “squish”) between the piston and cylinder wall in a 2-cycle engine. When this pressure is too low, the chainsaw will experience issues such as poor starting, lack of power, and excessive vibration. If you experience any of these symptoms with your chainsaw, it is likely to suffer from unstable compression. Luckily, there are several ways to fix an unstable chainsaw compression.

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The first step in fixing an unstable chainsaw compression is to check and adjust the spark plug gap. This gap should be set at 0.020–0.030 inches for optimal performance; if it’s not set correctly, the chainsaw won’t perform consistently or properly. To adjust the gap, use a feeler gauge and an adjustable wrench to loosen the spark plug’s screws. Once loose, carefully position the feeler gauge between the two electrodes on the spark plug and gently move it back and forth until the gap is set correctly.

The next step in fixing an unstable chainsaw compression is to check for any air leaks in the cylinder. If air enters through any cracks or holes, it will affect the engine’s ability to generate pressure, resulting in poor performance. To find any air leaks, inspect all of the seals around the cylinder for signs of wear or damage. If you notice any issues, replace them immediately with new parts.

Finally, if your chainsaw still has unresolved compression issues, it may be necessary to rebuild the engine. This is a more complex process and should only be attempted by experienced mechanics or professionals. The process involves disassembling the chainsaw and replacing any worn or damaged parts, as well as cleaning the internal components.


Checking compression on a chainsaw is an important part of maintenance and can help you keep your chainsaw running in top condition. By following the steps outlined above, you will be able to quickly and easily check your chainsaw’s compression levels. If your compression levels are too low, this could indicate a need for repairs or even that it’s time to replace the saw altogether. In any case, having regular checks of the engine’s compression will ensure that your chainsaw continues to perform its best for years to come. 


Q: What is the purpose of checking compression on a chainsaw?

A: Checking the compression helps identify any potential problems with the engine. It allows users to diagnose and fix issues such as low power, poor performance, or other mechanical problems.

Q: How often should I check my chainsaw’s compression?

A: It is recommended that you check your chainsaw’s compression every time you perform regular maintenance or after using it for an extended period of time. This will help prevent future problems from occurring and ensure optimal performance.

Q: What tools do I need in order to check compression on a chainsaw?

A: You will need either a special compression gauge or a regular air pressure gauge in order to properly measure the compression of your chainsaw. You may also need other tools such as a spark plug wrench or screwdriver depending on the make and model of your chainsaw.

Q: How do I use the compression gauge to check the engine?

A: First, remove the spark plug from the cylinder and attach the compression gauge or air pressure gauge directly into the spark plug hole. Next, pull on the starter cord multiple times while keeping an eye on the gauge’s reading. If it is within manufacturer-specified limits then your chainsaw’s engine is operating normally.

Q: What should I do if my chainsaw’s compression is low?

A: If the compression is too low, it indicates that there may be a problem with the engine and further investigation may be necessary. You can try replacing the spark plug or performing other maintenance tasks to troubleshoot the issue. If these measures don’t help, you should consult a qualified technician for further assistance.



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