Stihl Chainsaw Spark Plugs (Maximizing Performance)

Despite being a small component, a spark plug plays an important role in running a chainsaw. That’s why keeping an eye out for a bad spark plug and replacing it when necessary is vital.

It’s important to find a suitable replacement for Stihl chainsaw spark plugs when it’s time. 

Some Stihl models use the NGK BPMR7A spark plugs, whereas some use the NGK CMR6H spark plugs. These are the only two spark plugs you will find in Stihl chainsaws. So, you have to specify the model you are using and cross-match the spark plug with that model. 

This article covers everything from the chart you need to match the model to the signs of a bad spark plug. So, make sure to read till the end. 

Stihl Chainsaw Spark Plug Chart

The chart below will help you find which spark plug to use for your particular table saw. However, you can also find a suitable match in your chainsaw’s user manual:

Spark Plug Part Number Stihl Chainsaw Model
NGK BPMR7A 017, MS170, MS180, 019, MS191, MS192, 024, MS240, 025, MS250, 026,  MS260, MS261, MS270, MS271, 028, MS280, 029, MS290, MS291, 031, MS310, MS311, 039, MS390, MS391, 036, MS360, MS361, 044, MS440, MS441, 046, MS460, MS461, MS462, 066, MS660, MS661, 088, MS880, MS881.
NGK CMR6H MS171, MS181. MS193, MS194, MS211, MS241, MS362.

The spark plug number is always written on the spark plug to make it convenient for the user to identify the model. 


Stihl Chainsaw Spark Plug Size

Spark plugs are not specified using size as a unit. Instead, there’s an identical part number for every spark plug. This makes looking for a spark plug easier for a particular machine.

For instance, when you are using a Stihl chainsaw, the user manual will dictate the spark plug required. 

It’ll refer to particular spark plug numbers. This way, you can easily find the spark plug by searching for the number. The wrench size, however, required to remove spark plugs is important information.

You will need a 16 mm wrench for removing an NGK CMR6H spark plug and a 19 mm wrench for removing an NGK BPMR7A spark plug.

For carburetor adjustment, check my article on Stihl chainsaw carburetor adjustment.

Stihl Chainsaw Spark Plug Gap

The spark plug gap for Stihl Chainsaw may vary depending on the specific model and engine type:

Stihl Chainsaw Model Spark Plug Gap
Stihl MS 170 0.02-0.03 inches (0.5-0.6 mm).
Stihl MS 250 0.02 inches (0.5 mm).
Stihl MS 362 0.02-0.024 inches (0.5-0.6 mm).
Stihl MS 461 0.02-0.024 inches (0.5-0.6 mm).
Stihl MS 880 0.02-0.03 inches (0.5-0.8 mm).
STIHL MS180C  0.02-0.03 inches (0.5-0.6 mm).
STIHL MS290 0.02-0.03 inches (0.5-0.6 mm).
STIHL TS400 0.02-0.024 inches (0.5-0.6 mm).

Signs Of A Bad Spark Plug

The spark plug of your chainsaw is responsible for ignition. So, any trouble with starting the engine can mean that the spark plug is damaged. Here are a few signs to look out for:

  • It requires several attempts to start the chainsaw. 
  • The spark plug has visible damage like carbon buildup or is rusted. 
  • The chainsaw is consuming more fuel than it’s supposed to.  
  •  Rough runs or misfires. 

How To Check The Spark Plug?

Remove the cover of your Stihl chainsaw, and then remove the spark plug boot. Use the proper tool to remove the spark plug and then connect it to the boot.

Hold the boot-covered area of the spark plug and place it on top of the metal surface of your engine. Use the pull cord to check for sparks. 

Make sure not to touch the sparking area and the metal at the same time to avoid zapping yourself. Always hold the boot, which is a rubber part and will not zap you.

In addition, make sure that the chainsaw is empty if you want to keep it from starting when testing the spark plug.

You can also find test lights that let you check whether the spark plug is working. Avoid doing the test in a bright area because it can be difficult to see the spark or the light.

Here’s a video of the whole process to help you understand it better:


Safety Measures When Testing The Spark Plug

  • Avoid touching the end of the spark plug (where it sparks) to prevent shocks. 
  • Keep the chainsaw empty to prevent accidental starts. 
  • Use a low-lit area so that you can see the spark without any difficulties. 
  • Keep the spark plug away from the cylinder hole when testing it without a testing light. 
  • Only use compatible spark plugs for your particular chainsaw to avoid damage and improve performance. 
  • The safest option, especially when you’re not certain about the process is to take the chainsaw to a garage. 

Replacement Options

If you’re certain that your spark plug needs a replacement, you can consider the following options:

Spark Plug Part Number Features
CMR6H Universal fit.

Zinc-dipped shell.

Less carbon buildup.

BPMR7A Universal fit.

Copper core.

Corrosion-resistant plating.

Frequently Asked Questions

Are spark plug wrenches universal?

When you are considering the size of a wrench, it’s not universal. Different spark plugs will require a different size wrench. However, wrenches, in general, are universal, meaning that you can use the same wrench for different machines, considering that the size is right. 

How often does a spark plug need replacing?

According to Stihl, you should change the spark plug you are using after 100 hours of using the chainsaw. If it hasn’t been 100 hours, but your chainsaw is struggling to start, you should check if the spark plug has gone bad. 

How to determine what spark plug to use?

Stihl chainsaws only use two spark plugs, so it’s easy to determine. The safest option is to check the user manual of your chainsaw to check which spark plug is suitable. If you don’t have the user manual, you can find it online on Stihl’s website. 

Wrap Up

Using the right Stihl chainsaw spark plug can not only improve the performance of your chainsaw but also make it long-lasting. It’s one of those components that are mandatory for running the chainsaw smoothly. 

You will certainly face difficulties starting your chainsaw and keeping it running smoothly with a bad spark plug.

So, whenever you’re experiencing such issues, give it a check and replace it before making the situation worse.

Jim Boslice

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