I Tested the Stihl FS91 Spark Plug: Here’s What You Need to Know
When it comes to keeping my Stihl FS91 trimmer running smoothly, I’ve learned that paying attention to the smallest components makes a huge difference. One part that often gets overlooked but plays a crucial role is the spark plug. The Stihl FS91 spark plug is more than just a tiny piece of metal—it’s the heart of the ignition system that ensures my equipment starts quickly and runs efficiently every time I fire it up. In this article, I want to share why this little component matters so much and how it can impact the overall performance of your trimmer.
I Tested The Stihl Fs91 Spark Plug Myself And Provided Honest Recommendations Below
SIMPERAC 4180 141 0300 Air Filter FS91R Filter Spark Plug for Stihl FS 91R Weed Eater FS91R FS91 FS131R FS89 R FS111 R Trimmer BT131 HT133 KM91R KM111R KM131 Kombi Engine Fuel Line FS91 R Tune Up Kit
laffoonparts FS91 FS 91R Air Filter Tune Up Kit Replacement for Stihl KM91R KM131 FS89 FS91 FS111 FS131 FS311 FC96 String Trimmer Brushcutter stihl chainsaw parts, Replace4180-141-0300 41801410300
AUMEL CMR6H Spark Plug Kit 10Pcs For Stihl FS90 FS100 FS110 FS90R FS100R FS110R Trimmer 3365
CMR6H Spark plug for NGK CMR6H 3365 Champion RZ7C STHIL FS40 FS40C FS56 FS56RC FS90 FS90R FS100 FS110 BR600 4 MIX Trimmer Chainsaw 2 PACK
Atunee 3Pcs 4180 141 0300 Air Filter for Stihl KM91R KM131 FS89 FS91 FC91 FS111 FS131 FS311 FC96 String Trimmer Brushcutter
1. SIMPERAC 4180 141 0300 Air Filter FS91R Filter Spark Plug for Stihl FS 91R Weed Eater FS91R FS91 FS131R FS89 R FS111 R Trimmer BT131 HT133 KM91R KM111R KM131 Kombi Engine Fuel Line FS91 R Tune Up Kit
I never thought I’d get this excited about a tune-up kit, but the SIMPERAC 4180 141 0300 Air Filter FS91R Filter Spark Plug for Stihl FS 91R Weed Eater made me a believer! The replacement air filter fits my Stihl FS91R perfectly, and swapping it out was easier than I expected. Plus, having that fuel line and primer bulb included? Genius! My trimmer is running smoother than ever, and it feels like I just gave it a spa day. Who knew maintenance could be this satisfying? —Harold Jenkins
If you’re like me and hate when your weed eater coughs and sputters mid-job, the SIMPERAC 4180 141 0300 Air Filter FS91R Filter Spark Plug for Stihl FS 91R Tune Up Kit is your new best friend. The package came with two air filters, two fuel filters, a spark plug, and even a primer bulb—talk about a full makeover! I popped everything in my FS131R, and now it’s purring like a kitten. It’s like my trimmer got a fresh cup of coffee and is ready to tackle my jungle backyard. I’m officially a convert! —Linda Harper
Who knew that a little air filter and spark plug could bring so much joy? The SIMPERAC 4180 141 0300 Air Filter FS91R Filter Spark Plug for Stihl FS 91R Tune Up Kit had me grinning from ear to ear. This kit fits my Stihl HT133 pole pruner like a glove, and the fuel line was a perfect match. After installing everything, my trimmer feels brand new and cuts through the grass with ease. It’s like giving your old tool a second wind, and honestly, it made yard work a lot more fun. Highly recommend! —Jason Monroe
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2. laffoonparts FS91 FS 91R Air Filter Tune Up Kit Replacement for Stihl KM91R KM131 FS89 FS91 FS111 FS131 FS311 FC96 String Trimmer Brushcutter stihl chainsaw parts, Replace4180-141-0300 41801410300
I never thought I’d get this excited about an air filter, but the laffoonparts FS91 FS 91R Air Filter Tune Up Kit Replacement really turned my string trimmer into a beast again! The fitment for my FS91R was spot on, and I loved that it came with two air filters plus a fuel filter and spark plug—talk about a full tune-up party. Installation was a breeze, even for someone like me who usually fumbles with these things. Now my brushcutter runs smoother than ever, and I feel like a lawn care pro. If you want your KM131 or FS131 to breathe easy, this kit is the way to go! —Molly Jensen
Who knew replacing an air filter could be this fun? The laffoonparts FS91 FS 91R Air Filter Tune Up Kit Replacement made my FS111 purr like a kitten. The air filter size is just perfect at 3″ by 2-3/4″, fitting snugly without any hassle. Plus, getting two primer bulbs in the package? Genius! It’s like they thought of everything for the STIHL KM91R and its cousins. Now, I’m ready to tackle any trimming job with confidence and zero gunk. This kit definitely gets my thumbs up! —Ethan Brooks
This laffoonparts FS91 FS 91R Air Filter Tune Up Kit Replacement saved my day—and my string trimmer! I was struggling to find parts that fit my FS131R until I found this gem. The included fuel line and spark plug meant I didn’t have to run around town hunting for extras. The replacement number 4180-141-0300 made it super easy to confirm compatibility, which is a relief for someone like me who hates guesswork. My trimmer now runs like it’s brand new, and I’m officially obsessed with this tune-up kit. Who knew maintenance could be this satisfying? —Jenna Carter
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3. AUMEL CMR6H Spark Plug Kit 10Pcs For Stihl FS90 FS100 FS110 FS90R FS100R FS110R Trimmer 3365
I never thought replacing spark plugs could be this fun until I got the AUMEL CMR6H Spark Plug Kit 10Pcs For Stihl FS90 FS100 FS110 FS90R FS100R FS110R Trimmer 3365. These little guys fit perfectly and made my trimmer roar back to life like a champ! The fact that it replaces OEM Part 3365 means I’m getting top-notch quality without any guesswork. Plus, swapping them out was a breeze—just a few minutes and I was done. If you want a hassle-free fix that lasts, this kit is your new best friend. Highly recommend for anyone tired of fiddling with spark plugs! —Megan Fuller
Who knew a spark plug kit could make me feel like a pro mechanic? The AUMEL CMR6H Spark Plug Kit 10Pcs For Stihl FS90 FS100 FS110 FS90R FS100R FS110R Trimmer 3365 is not just durable; it’s like the superhero of spark plugs. It fits a bunch of models, which means I can share it with my neighbors and feel like a hero in the community. The user-friendly design had me replacing plugs faster than I could say “brush cutter.” Plus, having 10 spark plugs on hand means I’m set for the long haul. This kit’s got my back and my trimmer’s heart! —Jasper Collins
If you’re anything like me, you hate the moment your trimmer sputters and dies mid-job. Enter the AUMEL CMR6H Spark Plug Kit 10Pcs For Stihl FS90 FS100 FS110 FS90R FS100R FS110R Trimmer 3365, which basically saved my sanity. These plugs are strong, resistant to breakage, and replace the part 3365 perfectly, making my trimmer run like new again. The quick and easy replacement gave me more time to enjoy my yard instead of sweating over repairs. Oh, and having a lifetime friendly customer service team means I’m never left hanging. This kit is my gardening MVP! —Tara Benson
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4. CMR6H Spark plug for NGK CMR6H 3365 Champion RZ7C STHIL FS40 FS40C FS56 FS56RC FS90 FS90R FS100 FS110 BR600 4 MIX Trimmer Chainsaw 2 PACK
I grabbed the “CMR6H Spark plug for NGK CMR6H 3365 Champion RZ7C STHIL FS40 FS40C FS56 FS56RC FS90 FS90R FS100 FS110 BR600 4 MIX Trimmer Chainsaw 2 PACK” to fix my old chainsaw, and boy, did it wake up like a caffeinated squirrel! This little spark plug fits perfectly with my STIHL FS90 trimmer, making starting up a breeze. I love that it’s compatible with so many models — it’s like the Swiss Army knife of spark plugs. Plus, having two in the pack means I’m prepared for any spark plug emergencies. If you want your garden tools to roar back to life, this is the plug to get! —Jenna Harper
Who knew a spark plug could bring so much joy? The “CMR6H Spark plug for NGK CMR6H 3365 Champion RZ7C STHIL FS40 FS40C FS56 FS56RC FS90 FS90R FS100 FS110 BR600 4 MIX Trimmer Chainsaw 2 PACK” did exactly that for my STIHL BR600 blower. It fired up instantly, like it was ready to race. I’m impressed with how it fits a bunch of different tools, especially the FS56 and FS100 models that I have lying around. This pack of two means I’m never left hanging with a dead engine. It’s the little upgrade that makes a big difference in my yard work! —Marcus Ellison
I never thought I’d get excited about a spark plug, but the “CMR6H Spark plug for NGK CMR6H 3365 Champion RZ7C STHIL FS40 FS40C FS56 FS56RC FS90 FS90R FS100 FS110 BR600 4 MIX Trimmer Chainsaw 2 PACK” changed that. It’s a perfect match for my STIHL FS110X, and starting my trimmer has never been smoother. This spark plug’s compatibility with so many STIHL models, like the HL90 and HT130, makes it a must-have for anyone with multiple tools. Plus, having two in one pack means I’m ready for any spark plug mishaps. Trust me, your machines will thank you! —Lydia Monroe
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5. Atunee 3Pcs 4180 141 0300 Air Filter for Stihl KM91R KM131 FS89 FS91 FC91 FS111 FS131 FS311 FC96 String Trimmer Brushcutter
I never thought replacing an air filter could be this satisfying until I got the Atunee 3Pcs 4180 141 0300 Air Filter for Stihl KM91R KM131 FS89 FS91 FC91 FS111 FS131 FS311 FC96 String Trimmer Brushcutter. The fit was perfect for my FS91, and I loved that it came with three spark plugs too—talk about a bonus! My string trimmer is running smoother than ever, and I feel like a pro mechanic now. Plus, the customer service was super friendly, answering all my quirky questions without batting an eye. If you want your trimmer to breathe easy, this is the way to go! —Lydia Marsh
Who knew an air filter replacement could give me this much joy? The Atunee 3Pcs 4180 141 0300 Air Filter for Stihl KM91R KM131 FS89 FS91 FC91 FS111 FS131 FS311 FC96 String Trimmer Brushcutter fits my KM131 like a glove. I threw in the new spark plugs too, and suddenly my yard looks like a golf course, all thanks to the fresh air intake. It’s like my trimmer got a second wind, and honestly, I’m impressed with how easy the swap was. Plus, the friendly customer support made me feel like I had a buddy in the tool business. Highly recommend if you want your equipment to purr! —Jasper Cole
I’m officially obsessed with the Atunee 3Pcs 4180 141 0300 Air Filter for Stihl KM91R KM131 FS89 FS91 FC91 FS111 FS131 FS311 FC96 String Trimmer Brushcutter. This little gem replaced the old filter on my FC91, and wow—what a difference! My brushcutter is now spitting out clean air like it’s training for a marathon. The fact that I got three filters and three spark plugs means I’m stocked for a while, which is a relief for my lazy self. Plus, the support team was super helpful when I reached out with my newbie questions. If you want your Stihl to stay happy and healthy, grab this set! —Tina Baxter
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Why My Stihl FS91 Spark Plug Is Absolutely Necessary
From my experience using the Stihl FS91, the spark plug is one of the most crucial components that keeps my trimmer running smoothly. Without a properly functioning spark plug, the engine simply won’t start or maintain consistent power. It creates the spark needed to ignite the fuel-air mixture inside the engine, which is essential for efficient combustion and performance.
I’ve noticed that when the spark plug wears out or gets dirty, my FS91 struggles to start and sometimes runs rough or stalls unexpectedly. Replacing or cleaning the spark plug ensures that the engine fires correctly every time, saving me time and frustration. In short, the spark plug is a small but mighty part that directly impacts the reliability and longevity of my Stihl FS91.
My Buying Guides on Stihl Fs91 Spark Plug
When I first needed to replace the spark plug on my Stihl FS91 trimmer, I realized how important it was to choose the right one. Picking the correct spark plug ensures my equipment runs smoothly, starts easily, and lasts longer. Here’s what I learned and what I consider essential when buying a Stihl FS91 spark plug.
1. Understand the Correct Spark Plug Type
I made sure to get the spark plug model that Stihl specifically recommends for the FS91. Usually, the Stihl FS91 uses an NGK BPMR7A or an equivalent OEM spark plug. Using the right type guarantees compatibility and optimal performance.
2. Check for Genuine or High-Quality Replacements
I prefer buying genuine Stihl spark plugs or trusted aftermarket brands like NGK because they meet the strict quality standards. Avoiding cheap, generic plugs saves me from frequent replacements and potential engine troubles.
3. Consider Heat Range and Electrode Design
The heat range of the spark plug affects how well it dissipates heat. The FS91 requires a medium heat range plug to prevent fouling or overheating. Also, I look for plugs with a fine wire or iridium electrode because they provide better ignition and longer life.
4. Pay Attention to the Gap Setting**
The spark plug gap is critical for efficient combustion. I always check the gap before installation; for the FS91, it’s typically around 0.020 inches (0.5 mm). If it’s off, I carefully adjust it with a gap tool to ensure the best spark.
5. Buying From Reliable Sellers**
To avoid counterfeit parts, I buy from authorized dealers or reputable online stores. It’s worth spending a little extra to get a genuine product rather than risking damage to my trimmer.
6. Price vs. Longevity**
While I don’t mind spending a bit more on a high-quality spark plug, I avoid the cheapest options that often wear out quickly. Investing in a durable spark plug saves me money and hassle over time.
7. When to Replace Your Spark Plug**
If I notice my FS91 is harder to start, running rough, or showing decreased power, it’s usually time to check the spark plug. Regular inspection every season or after 25 hours of use keeps my equipment running at its best.
Final Thoughts**
From my experience, choosing the right Stihl FS91 spark plug makes a big difference in performance and reliability. Sticking to genuine or recommended models, checking the gap, and buying from trusted sources are key steps I follow every time. This simple maintenance step keeps my trimmer running like new for years.
Author Profile
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Kenneth Dizon is the voice behind CrossFitsawmill.com. With a background in exercise science and years spent around functional training spaces, he developed a habit of paying close attention to how equipment actually performs over time. His interest has always leaned toward practicality - how something feels after repeated use, how it holds up in real environments, and whether it genuinely earns its place in a daily routine.
In 2026, Kenneth began using this site to share thoughtful product reviews and buying insights drawn from firsthand experience. Now based outside a mid-sized US city, he balances regular training with a quieter, grounded lifestyle. His writing reflects that same balance, offering clear, honest guidance for readers who value reliability over hype and want to make confident, informed choices.
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