How Much Compression Should A Chainsaw Have?

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As per expert reviews and tests, a standard chainsaw should have a compression of around 110psi. Specific chainsaw engines might demand a bit of high or low compression for serving the purpose. Apart from that, the temperature of that tool is also an important aspect, which impacts the compression readings.

You might notice that a chainsaw runs faster when it generates more heat over the engine and slower when it is cool. Now, let’s check out details about the compression requirement for a chainsaw. 

How Much Compression Should A Chainsaw Have?

You need to keep track of the compression rating of your chain saw. And for that, you need to seek testing efforts to ensure that your compression doesn’t deviate from the expected figures. For example, some chainsaws come with a 2-cycle engine that demands compression of 110-140psi. Anything less than that won’t allow the 2-cycle chainsaw to even start.

Man using a chainsaw to cut wood log

If you are unaware of how much compression a chainsaw should have, you need to know how to test it! Therefore, follow this guide to learn about the ideal process of measuring the compression of your chainsaw

Step 1: Check The Motor Capacity 

You will find different chainsaw models with different capacities. And that motor capacity is denoted by the unit ‘cc.’ In fact, the usual chainsaw engines can have the lowest of around 30cc motor capacity.

In contrast, it can go higher up to 150cc. People mostly prefer 50cc chain saws for most of the applications. Also, higher cc motors are preferable for high-capacity engines only.

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A chainsaw that comes with a 50cc motor will have a compression level of around 140 to 150psi. And for the engine that has a motor of 60cc or above might possess compression levels of around 150 to 160 psi. 

Step 2: Check The Temperature Of Chainsaw

As per the thermodynamics rule, a cold chainsaw intends to run slow and is fast when it is hot. Therefore, when the chainsaw is cold or is at the initial stage of starting, it will demand a compression level of 85 to 100psi from vacuum air. But, in the case of a hot chainsaw engine, it will demand a compression of around 160psi from vacuum air. 

The hotness and coldness of the engine don’t demand compression from the internal motor. Hence, it requires compression from vacuum air, resulting in which the engine won’t produce the necessary compression. 

Step 3: Implement The Compression Test

Man checking the compression of his chainsaw
  1. You will need pressure-testing gauges to carry out this test. 
  2. Get a wrench or ratchet that will be essential for disassembling the spark plug from the chainsaw engine. 
  3. Now, make use of an adaptor that will hold the chainsaw, and use a gauge. 
  4. A gauge is primarily available in varying sizes, for which an adaptor is essential to make it compatible with the chainsaw
  5. Ensure to keep the gauge in the ideal place and pull the starter rope continuously.
  6. Stop pulling the starter rope only when you notice that the gauge needle stops its movement. 
  7. Now, go ahead and check for the number within the gauge, where it stopped. 
  8. The number is your ultimate compression figure of that particular chainsaw
  9. The standard compression range is around 110psi, and you need to compare the obtained rating with it. 
  10. If you find the measured figure similar or near about 110psi, then your chainsaw has a standard compression rate. 
  11. If it doesn’t match, then you need to consider enhancing the potential of compression in your chainsaw engine. 

Here is the video to give you a visual demonstration of how you can test the compression rate on your chainsaw engine. Check it out right away

Step 4: Rope Pulling Test For Compression

It is an easy and convenient way of predicting whether your chainsaw meets the standard compression rating or not. However, it is not the method that will determine accurate readings but will give an idea about whether your chainsaw is well-functional or not. 

  1. Lift the chainsaw off the ground with the use of its rope handle. 
  2. If this rope pulls out slower than usual, you can conclude that the chainsaw compression rate is less than essential. 
  3. If you get a tight hold over the cable with its engine, then you can figure that your chainsaw has well-functional compression. 
Chainsaw

Frequently Asked Questions

What Leads To Loss Of Compression In A 2 Stroke Chainsaw Engine?

The potential reason for which the 2-stroke chainsaw engine loses compression is a problem within head gasket or piston rings. Breakage of piston rings might be a reason for the loss in compression. For example, if the piston breaks into two pieces, then one of them might escape out from the exhaust of the chainsaw.

Hence, this, in turn, can cause the motor to face low compression issues. 

What To Do If My Chainsaw Lacks Power?

Compression is just one of the many reasons that might lead to loss of power in your chainsaw. In addition, there might be faults in many parts of your chainsaw, and you need to test them all for the purpose. Apart from the compression test, you should also consider checking the carburetors, air filters, pistons, mufflers, etc.

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To know about applying all these parts within a chainsaw, you can refer to this article

Conclusion

Compression troubles might show up if your gasket is leaking, crankshaft seals are out, or due to a problem in any internal engine part. Hence, you need to reach out to the root of the problem and find the exact issue that is causing compression hassles in your chainsaw. Small leakages are repairable, whereas broken parts need replacements.

So, you might have to get the parts yourself or reach out to a professional to carry out the replacements.

An expert at home repair, remodel, and DIY projects for nearly 40 years. His first experience came in completely restoring an antique home. Completely redone from the inside out, and restored to its original form, the home is a featured design by renowned Southern California Architect Cliff May, considered to be the father of the California Ranch Home. Now Dennis spends his time on fine woodworking projects and tool comparisons.