What is a Spark Plug Gap on a Chainsaw? [Applications Explained]

Patrick McMann

Knowledge Based

Are you facing some issues with your chainsaw lately? Is it hard to start, or have you noticed its poor engine performance? That could be because of an incorrect spark plug gap. Now, if you’re wondering, “What on earth is a spark plug gap, and how can it affect chainsaw engine performance?” 

Don’t worry. In this article,  I’ll help you understand what a spark plug gap is all about. I’ll also share why a gap is crucial in your cutting tool’s performance. Plus, you’ll learn the steps for measuring and adjusting the spark plug gap properly. So, stick around!

understanding the spark plug gap on a chainsaw

What Is the Spark Plug Gap on a Chainsaw?

A spark plug gap on a chainsaw is the space between the center and ground electrodes of the plug. This space is crucial in determining the strength of a spark when the spark plug fires to start the cutting machine. 

If the gap is too wide, the spark won’t ignite the air-fuel mixture in the combustion chamber, thus causing the cutting machine to misfire or not start at all. While a too-narrow gap will produce a spark that will be too strong and which can damage the spark plug or engine. 

So what is the correct chainsaw spark plug gap?

In handheld chainsaws with a 28-32 cc engine range, such as Stihl chainsaws, the standard spark plug gap is 0.020 inches (0.5 mm). However, for more powerful engines in the range of 38-55 cc, an optimal spark plug gap is 0.025 inches (0.635 mm). 

But I recommend referring to the manual provided by your chainsaw manufacturer. Or get in touch with an authorized servicing dealer in your vicinity to ensure you have the accurate spark plug gap. 

You can also measure the spark plug gap yourself with a feeler gauge and adjust it with a spark plug gap tool. But you must have experience in dismantling and reinstalling chainsaw components.

How to Measure a Spark Plug Gap?

Here’s how you can measure a spark plug with a feeler gauge:

Step 1: Gather Tools

Gather the tools such as a feeler gauge, wrench, and wire brush.

Step 2: Remove and Clean the Spark Plug

Next, remove the spark plug from the chainsaw with the help of the spark plug wrench. After that, use the wire brush to clean the dirt from the spark plug electrodes. This will help you accurately measure the spark plug gap.

Step 3: Measure the Spark Plug Gap

Take the feeler gauge and put the correct thickness gauge into the space between the center and ground electrodes. The center electrode will look like a small metal piece sticking out, while the ground electrode will be the bent metal piece surrounding the center electrode. 

Make sure the gauge fits snugly in the space. If the gauge feels too loose, it means the spark plug gap is too wide. On the other hand, if the gauge feels too tight, it indicates the spark plug gap is too narrow.

Now you know how to check the spark plug gap, let’s move on to adjusting it.

How to Adjust Spark Plug Gap on a Chainsaw?

Here are the steps for adjusting the spark plug gap on your cutting machine:

Step 1: Check the Spark Plug Gap for your Specific Model 

Start by checking the recommended spark plug gap for your specific chainsaw model. You can find this information in the chainsaw’s user manual or by contacting the manufacturer.

Step 2: Disconnect the Spark Plug Wire

Disconnect the spark plug wire to prevent any accidental ignition while working, and make sure to turn off your cutting tool.

Step 3: Adjust the Gap

You’ll need a suitable tool like pliers to adjust the space in the spark plug. Gently bend the ground electrode with the pliers, careful not to exert excessive force or damage the electrodes. You can bend the electrode to increase or decrease the gap as needed.

Step 4: Check the Gap Periodically

Continuously check the gap using the feeler gauge to ensure it matches the recommended specification. If you feel the gap doesn’t align correctly with the recommendation, continue adjusting until it reaches the desired measurement.

Step 5: Reinstall the Spark Plug

Once you’ve adjusted the gap accurately, carefully reinstall the spark plug into the chainsaw. Ensure it threads properly and tighten it by hand to avoid cross-threading, which can cause damage. Finally, reattach the spark plug wire.

Chainsaw Users Also Ask

Why does my chainsaw have trouble starting even with a properly gapped spark plug?

If your chainsaw is having trouble starting despite a properly adjusted spark plug gap, there are many reasons behind this. Firstly, it could be due to a fuel delivery problem caused by a clogged fuel filter, faulty fuel pump, or carburetor issues

Secondly, a dirty air filter or an intake valve issue may restrict the cutting machine from drawing in sufficient air, which is crucial for starting. A bad spark plug, faulty ignition coil, or problems with the ignition switch can also be the reasons.

Lastly, low engine compression resulting from worn piston rings, a blown head gasket, or a cracked cylinder can hinder the chainsaw from starting. However, you should conduct a further inspection. Take your cutting tool to a technician so they can accurately identify the underlying cause and resolve the issue.

What is the spark plug gap for a Stihl chainsaw?

The standard spark plug gap for a Stihl MS170 chainsaw is 0.020 inches (0.5 mm). This measurement is also standard for other cutting tool brands. However, it’s a good idea to consult the manufacturer’s manual to confirm the recommended spark plug gap for your specific cutting machine model.

How often should I check the spark plug gap on my chainsaw?

How often you should check the spark plug gap on your chainsaw depends on how frequently you use it. If you use the tool often, check the spark plug gap every 100 hours of use. On the other hand, if you use the cutting machine less frequently, you can extend the interval and check the spark plug gap every 200 hours of use. 

Final Thoughts

If you encounter problems starting your chainsaw or with its engine performance, it may be due to an incorrect spark plug gap. Therefore, regularly check and adjust it appropriately. But don’t forget to check your chainsaw’s manufacturer manual for the recommended spark plug gap, as different models may have slight variations. 

Remember knowing what is the spark plug gap on a chainsaw and how to adjust it is vital for avoiding potential incidents and maintaining your tool’s safe performance.

Patrick McMann