How much compression should a leaf blower have?

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Leaf blower engines just like any other engine are pressurized and the engine should maintain a certain level of compression to run properly. As long as your leaf blower’s engine is in optimal condition and you are performing regular maintenance, your leaf blower shouldn’t lose compression. But how much compression should a leaf blower have to work properly?

A leaf blower engine should have at least 90 psi of compression to start. For leaf blowers with bigger engines, the compression rating can be between 100-150 psi. If a leaf blower has a compression reading of less than 90 psi, it will be difficult to start and to run properly. A leaf blower requires 100 psi of compression.

The compression of a leaf blower engine indicates the amount of pressure being produced inside the cylinder of the engine. With normal compression, a leaf blower can produce more air pressure, therefore, making it easier to blow away any leaves. On the other hand, if there is not enough compression, the leaf blower will produce very little power and can even fail to start at all. Luckily checking the compression of a leaf blower is not difficult and you can do it yourself without taking the leaf blower to a mechanic. In this article, we are going to explain how to do it.

How much compression should a leaf blower have? 1

How much compression should a leaf blower have?

Leaf blowers use 2 stroke engines ranging between 30 to 50 cc. While the minimum compression a 2 stroke engine needs to complete the combustion process is 90 psi, you cannot expect a leaf blower with such a low compression reading to produce much power. Even a small 30 cc leaf blower engine should have a reading of 100 psi according to most manufacturers. The same goes for chainsaws as well since leaf blowers and chainsaws have similar engine sizes. The compression reading of a leaf blower when it is not warmed up can be 90psi, but as the leaf blower engine warms up, it will have difficulties running with 90 psi of compression. A warmed up leaf blower should have around 100 psi of compression to produce the maximum power output.  Anything less than 90psi means that there is a loss of pressure in the leaf blower’s engine which also causes loss of compression.

How to check the compression of a leaf blower?

Testing the compression a leaf blower is a simple task and it is going to take roughly 2 minutes to check your leaf blower’s compression. A compression test can be done on a leaf blower that is not running properly or has poor power output while it is running. To test the compression of your leaf blower engine you need a specialized tool known as compression tester. Make sure that you have a compression tester that is specifically designed for testing engine compression of small engines. A compression tester gauge is a very handy tool and it can be bought for less than $30 from any hardware store. You can check the compression of your leaf blower engine through following simple steps:

Step 1. If your leaf blower has a cylinder cover you will have to remove it to access the sparkplug of your leaf blower. In order to remove the cover, you will need a screwdriver to undo the screws and take the cylinder cover off.

Step 2. Remove the sparkplug boot from the sparkplug by gently pulling it off the sparkplug. Avoid pulling the sparkplug boot by the wire, you can use a screwdriver to loosen up the boot and remove it. After removing the sparkplug boot, move it aside and you will be able to find the sparkplug underneath it.

Step 3. Now in order to test the compression inside your leaf blower engine, you have to connect the compression tester in such a way that compression doesn’t escape from the engine. And the only way to safely do that is by connecting the compression tester in the place of the sparkplug. But first, you have to remove the sparkplug itself.  To do that, you need to use a correct sized socket wrench to fit your sparkplug and loosen the sparkplug up in order to remove it from the engine of your leaf blower.

Note: Make sure to place the sparkplug on a clean surface and prevent any debris or dirt from getting onto the sparkplug because debris can enter the engine of your leaf blower when you reinstall the sparkplug.

Step 4. Next, take the fitting end of your compression tester kit and fit it onto the sparkplug hole threading by turning it clockwise. Make sure not to overtighten the fitting onto the sparkplug hole as it can damage the threading. You don’t have to use a socket wrench to fit the compression tester on the sparkplug hole and you should only use your fingers for this step.

Step 5. With the compression tester kit attached to your leaf blower’s engine, you will have to pull the starting cord up to 5 times in order to get a compression reading. The leaf blower will not turn over because the spark plug is missing but you will notice the needle of the compression tester move upwards every time you pull the starter cord. After 2  or 3 pulls the needle on the gauge of compression tester will stop climbing further which is an indicator that your leaf blower engine has reached its peak compression.

Note: If you have a leaf blower with an electric starter, simply turn on the starter for a few seconds until the gauge of the compression tester has reached its max reading.

Step 6. An ideal compression reading would range between 90 and 110 psi for a cold leaf blower. If your leaf blower shows a compression reading of less than 90psi, then it is an indicator that your leaf blower has a compression leak and it is not producing optimal compression.

How to fix a leaf blower with a low compression rating?

So you have tested your leaf blower’s compression using the method explained above and it turns out it has a compression rating lower than 90psi. Now you must be wondering how can you fix the loss of compression in your leaf blower. It is important to know that compression loss happens due to a pressure leak from the engine. To fix the low compression issue you have to pinpoint the location where the compression is being leaked from. Some common places where the compression might be leaking from include:

  • Sparkplug hole: It is possible that the sparkplug is loose and it is not fitting properly inside the hole causing a loss of compression. A great way to test if the sparkplug is properly fitted or not is by trying to rotate it by hand. If it moves freely then it is a sign that the sparkplug of your leaf blower is loose or the threading has worn out, causing loss of compression. In this case, you will have to replace the threading as well as the sparkplug of your leaf blower.
  • Cracked cylinder head: Cylinder head of your leaf blower engine is where all the compression is produced and if the cylinder head is damaged or cracked it can result in loss of compression. The only way to solve this is by replacing the cylinder head and installing a new cylinder head that fits the engine perfectly.
  • Damaged Gasket: One of the most common causes of loss of compression is damaged gaskets. Gaskets are put in place in order to seal the different components of an engine together without losing compression. So as soon as a gasket gets damaged your leaf blower will start to lose compression. To fix a damaged gasket, you will have to disassemble the engine and replace the damaged gasket with a new one.
  • Loose bolts: Engine of your leaf blower is held together with the help of bolts and if any of these bolts especially the ones holding the cylinder head in place get loose, you can expect significant compression loss. Luckily fixing loose bolts is as simple as it gets. All you have to do is get the correct sized socket and tighten the bolts up to fix the compression leakage.

Apart from the above-mentioned causes of compression loss, internal issues such as bad piston rings and worn out valves can also cause loss of compression in your leaf blower. If that is the case you will require professional help from a small engine mechanic because an internal engine compression leakage requires special tools and expertise to fix it.

Conclusion

A leaf blower with optimal compression makes the job of blowing dry leaves easy and efficient. Therefore you should make sure that your leaf blower maintains a compression reading between 90-110 psi which is a sign that your leaf blower is functioning properly.