Petrol-driven chainsaws are powerful beasts, but it doesn’t take much for them to stop working. Even when you have a high-quality chainsaw from a giant brand like Stihl, you might wake up one day and see that your chainsaw is not working as it should.
That’s exactly what happened to me one day. I woke up, had my morning cup of coffee, and wanted to head out to get some work done with my chainsaw.
But once I tried to do a test on my chainsaw, the engine simply refused to fire up. For the life of me, I couldn’t figure out what went wrong with it at the time.
The engine was fine, and the fuel tank was filled, but still, the chainsaw wouldn’t ignite.
After a few hours of checking, I discovered that my spark plug was damaged. Thankfully, I keep a few spare spark plugs for Stihl chainsaws at the workshop, so fixing my chainsaw wasn’t too difficult.
If you are facing issues with the engine of your chainsaw, and the spark plug is the culprit, replacing it is usually the only option. But which spark plug do you need for your Stihl chainsaw? Well, that’s exactly what I want to discuss in this article, so let’s get started.
Types of Spark Plug in Stihl Chainsaw
Stihl chainsaws, as you are well aware, offer reliable performance, and one of the main reasons for it is their high-quality spark plugs. Most Stihl chainsaws are shipped with specialized NGK spark plugs with high-end components and materials. However, using a Bosch spark plug as an alternative can also work when you change them.
But spark plugs don’t last forever, and eventually, you will have to replace the one that you have in your chainsaw once it gets damaged or old. So let me give you a quick reference guide for the spark plugs used in Stihl chainsaws to help you find the right replacement for your chainsaw.
Stihl Spark Plug Chart
Here’s a quick chart for an overview of the spark plugs used in Stihl Chainsaws.
| Stihl Chainsaw Models | Bosch | NGK |
|---|---|---|
| 009, 010, 011, 012, 015, 017, 018, 019 T, 191 T, 020 T, 021, 023, 024, 025, 026, 029 S, 034, 036, 360, 039, 041, 044, 046, 064, 066, 070, 076, 088 | WSR6F | BPMR7A |
| MS 170, 180, 192 T, 200, 200 T, 201, 201 T, 210, 230, 250, 260, 261, 270, 271, 280, 290, 291, 310, 311, 361, 362, 390, 391, 440, 441, 460, 650, 660, 88 | WSR6F | BPMR7A |
| MS 150, 171, 181, 192 C-E, 193, 211, 241, 25 | – | CMR6H |
The NGK BPMR7A is the classic spark plug used in many high-quality, small-engine machines such as chainsaws, trimmers, weed whackers, etc. It comes with a copper core center electrode to improve electrical conductivity and enhance heat transfer. In addition, the nickel alloy outer electrode in it resists corrosion.
The spark plug has a thread diameter of 14mm and has a resistor inside to reduce electromagnetic interference. It’s a time-tested spark plug that provides reliable performance for many outdoor gears. And that is why this is the spark plug of choice for most of the Stihl chainsaws, both in the past and present generations.
The Bosch WSR6F is often considered the alternative to the NGK BPMR7A. Similar to the NGK spark plug, the WSR6F comes with a thread diameter of 14mm and a reach of 19mm. It also has a nickel alloy center electrode for better corrosion resistance.
And the outer copper core improves heat transfer and electrical conductivity. The main appeal of the WSR6F over the BPMR7A is that it has a tapered cut ground electrode which is known to improve the fuel efficiency of the engine. It also comes with a resistor to cut out radio frequency noise and electromagnetic interference.
If the old NGK spark plug in your Stihl chainsaw wears out, you can replace it with the Bosch WSR6F without any issues.
While the NGK BPMR7A is considered the norm for most Stihl chainsaws today, when the MS series was in its infancy, the manufacturers went with the CMR6H spark plug. Performance-wise, there isn’t any real difference between the two spark plugs. They even have the same construction design.
But the thread diameter of the CMR6H is smaller at only around 10mm. Its reach is also only 12.7mm. What that means is that if your Stihl chainsaw uses the CMR6H spark plug, you won’t be able to replace it with the BPMR7A or WSR6F as the thread won’t match. The CMR6H is the only choice here.
What’s the Role of Spark Plug in Stihl Chainsaw?
A spark plug is a relatively simple component, but one that’s essential to the ignition of any petrol-drive engine, such as the ones found in a chainsaw. As the name suggests, it is responsible for producing the spark that ignites the fuel mixture in the combustion chamber of your engine.
There are only three parts in a spark plug – the metal shell, an insulator, and the electrodes. But each of these three parts has a specific role to play in the overall process.
- Metal Shell
The metal shell surrounds the insulator and supports it. It is also the part that gets installed in the engine. The ground electrode is located at the bottom of the shell so that current can pass through the engine to the center electrode.
- Insulator
It falls on the insulator to insulate the terminal, the center shaft, and the center electrode from the metal shell to prevent high voltage from coming out of the electrodes.
- Electrodes
There are two electrodes used in a spark plug. Firstly, there’s the center electrode that extends from the metal shell, and then there’s the ground electrode that is fixed inside the shell. When you turn on the engine, the spark travels from the ground electrode to the center electrode to fire up the ignition process.
A faulty spark plug can quickly lead to malfunction, even in a high-end chainsaw. So, make sure your spark plug is getting enough attention whenever you detect any engine issues in a chainsaw.
My Preferred Spark Plug for Stihl Chainsaws
Just like how there are many amazing chainsaws brands, there are many brands that manufacture quality spark plugs. But there are also some that are downright rip-offs. I have had my fair share of poor investments, and now I have a decent idea of which spark plugs are worth buying and which ones to avoid.
So let me share some of my expertise and help you find the best spark plug for your Stihl chainsaw.
- HIFROM 5PCS Spark Plug
The 5pcs Spark Plug set by HIFROM is a great choice for anyone looking to get decent value and quality with their investment. Since it comes as a set of 5, you will have a few plugs left over for later.
The main highlight of the spark plug is its multi-ribbed insulator that prevents misfires and ensures proper ignition. In addition, the nickel-plated shell in the plug also provides amazing resistance to corrosion, enhancing its durability and minimizing your maintenance responsibilities.
Installing the plug is also pretty easy and straightforward. And it’s also priced quite low. That’s why I like to buy a couple of them and keep them in stock for when I need to replace the spark plug in my chainsaw.
- BPMR7A NGK Spark Plug
Of course, nothing beats the reliability of the OG BPMR7A spark plug by NGK. It’s the one that comes originally with your Stihl chainsaw and the one that’s guaranteed to perform well without any issues.
Needless to say, the main appeal of this spark plug is its originality. The heat transfer and electric conductivity of this plug are top-notch and ensure proper ignition when you install it into your chainsaw. So, if you want a hassle-free replacement for your old spark plug – this is the one you need.
The main downside to it, though, is that it’s expensive and comes as a set of one. So, if you are stocking up on backup spark plugs, this might not be the best choice. However, as a replacement, there’s no doubt that the NGK BPMR7A is an amazing option to go with.
- 5 Pack BM6A Spark Plugs by P SeekPro
Chinese brands often get a bad rep for their electrical components. So naturally, I was a bit skeptical when I found the BM6A spark plug set by the brand P SeekPro. But still, I wanted to try it out because of its low price.
And if I’m being honest, I was quite happy with its durability after trying it out for myself. The thread diameter with the plug is 14 mm which is a bit bigger than most Stihl chainsaw’s original spark plugs. Thankfully I didn’t find any issues when setting it up. The spark plug went in easily.
In terms of design and construction, it’s a pretty standard gasket-style spark plug. It has copper electrodes for quality heat transfer, and the durability is also quite decent. So, if you want a cheap spark plug set that you can keep around as backup, this is a great one to go with.
Be on the Lookout When Looking for a Spark Plug for Stihl Chainsaws
There really isn’t much to think about when you are buying a spark plug for your Stihl chainsaw. But then again, I’m sure you have come across some spark plugs that are more expensive than others. So, there are certainly a few things that can affect its performance.
In this section, I will talk about a few key considerations when you are planning to replace your Stihl chainsaw’s spark plug.
- Compatibility
The most important thing about spark plugs is to get the ones that are compatible with your chainsaw. Now the NGK BPMR7A is the standard choice for most of the old or current-gen Stihl chainsaws out there. You can also go with the Bosch WSR6F if you wish.
However, if you have a Stihl MS 150 or MS 171, for instance, going with these two spark plugs won’t cut it. In that case, you will need to go with the NGK CMR6H spark plug. So, make sure you read up on the spec sheet of your chainsaw when you are getting your spark plug.
- Material
The main thing that affects the price, and also the durability of a spark plug, is the material used in its construction. Copper is the classic choice of material for most plugs available in the market, and it’s also the cheapest. But these days, there are a few more materials that manufacturers use to give the plugs a better lifespan.
Platinum is a good choice of material as it offers a better lifespan for your spark plug while keeping its cost low. But if you don’t mind spending more, you can go with double platinum or iridium spark plugs. Of course, there’s nothing wrong with the good-old copper plug too.
- Quantity
When it comes to buying new spark plugs, there’s value in quantity. You see, spark plugs are pretty cheap, and even a high-end plug shouldn’t cost you much. But going out and buying a single spark plug every time you need to replace the one in your chainsaw doesn’t seem very practical if you ask me.
Instead, what you should do is keep a couple of spark plugs as a backup in your workshop. That way, whenever your old plug is damaged, you can swap it out with a new one from your inventory. And going with a set of 5 or 10 spark plugs is the best way to stock up on some backup spark plugs.
Why Do Spark Plugs Go Bad?
Like any other mechanical component, spark plugs do not last indefinitely. While regular maintenance and cleaning of the chainsaw can prolong its lifespan, inevitably, a spark plug will require replacing.
The primary cause of a spark plug going bad is carbon build-up which occurs when you don’t clean your chainsaw engine regularly. Dust can accumulate near the engine, which can also weaken the electrode and result in poor ignition from the plug.
And once your spark plug is damaged, your only right course of action is to replace it. Thankfully, replacing a spark plug is pretty easy, and it’s not that expensive either.
How to Replace a Spark Plug in Stihl Chainsaws
If you own a Stihl chainsaw, you will need to be prepared to change its spark plug eventually. But the truth is many homeowners who use chainsaws for property maintenance around the house don’t really know much about it.
So let me quickly drop a few pointers on how you can easily replace the spark plug in Stihl chainsaws.
Step – 1
The first step is to unlock the shroud in your chainsaw’s crankcase. For Stihl chainsaws, you need a flathead screwdriver to unlock it. Then take the shroud off gently.
Step – 2
You should notice the air filters right away at the top of the machine. Lift it up and remove the rubber cap to access the spark plug.
Step – 3
You now need a 19 mil hex socket spanner to loosen the spark plug. Once it’s loose, you can remove the spark plug by hand.
Step – 4
Now all you have to do is put the new spark plug and insert it into the socket. You can tighten it a bit by hand and then use the socket spanner to tighten it up.
Step – 5
Next, put the rubber cap back in its place and reinstall the air filter. This is a good chance to clean or replace your air filter if it is dirty. Once everything is back in its place, close up the crankcase and try starting your chainsaw. If it had been malfunctioning because of a faulty plug, it should normally work now.
Sometimes it might be necessary to reset the gap in your spark plug if it’s not set properly. For more information on this, check out my article on spark plug gaps for Stihl chainsaws.
Some Words of Wisdom
Replacing the spark plug in your Stihl chainsaw is inevitable, even when you take good care of your chainsaw.
So, it’s always a good idea to stock up on a couple of spare spark plugs. That way, you will be able to replace it straight away if your chainsaw refuses to turn on.
Now the spark plug that you pick will largely depend on the chainsaw that you own. Just make sure you get a few extra ones so that you can store them away for later.
And also, don’t go with the cheapest ones you can find on the market. Spending a couple of extra bucks is a good idea if it gets you a spark plug that lasts longer.
I hope my in-depth discussion on the best spark plug for Stihl chainsaws could help you get a better idea about this delicate but essential component. Good luck!
