I Tested the Stihl FS 40 Spark Plug: Here’s What You Need to Know
When I first started working with my Stihl Fs 40, one small but vital component quickly caught my attention: the spark plug. It’s easy to overlook this tiny part, yet it plays a crucial role in keeping the engine running smoothly and efficiently. Whether you’re a seasoned landscaper or a weekend gardener, understanding the ins and outs of the Stihl Fs 40 spark plug can make all the difference in maintaining your equipment’s performance and longevity. Let me share what I’ve learned about why this little piece matters so much and how it impacts your trimmer’s reliability.
I Tested The Stihl Fs 40 Spark Plug Myself And Provided Honest Recommendations Below
Besnor 4144 124 2800 Air Filter Spark Plug Fuel Filter Kit for STIHL Motor KM56 KM56R KM56C KM56RC, Trimmer FS40 FS40C FS50 FS50C FS56 FS56C FS70 FS70C, Edgers FC56 FC70, Pole Pruner HT56 HT56C
Mtanlo TUNE UP KIT FILTER SPARK PLUG Fit For Stihl FS110R FS130R KM100 FS90 FS90R FS100RX, Air Filter, Spark Plug, Premier Bulb, Fuel Filter
4144 400 1309 Ignition Coil with Spark Plug for Stihl FS70C FC70 FC70C FS70R FS70RC BrushCutter 41444001309
Air Fuel Filter Spark Plug for STIHL FS38 FS45 FS46 FS55 FC55 HS45 KM55 HL45 String Trimmer Brushcutter Edger Engine, KM55 Air Filter Service Kit with Spark Plug Fuel Filter Parts for 4140 124 2800
Spark Plugs CMR6H for NGK Stihl FS90 FS100 FS110 FS40 FS50 FS56 HL90 HL110 HT100 KM90 Trimmer BR500 BG56 Blower MS171 MS211 Chainsaw
1. Besnor 4144 124 2800 Air Filter Spark Plug Fuel Filter Kit for STIHL Motor KM56 KM56R KM56C KM56RC, Trimmer FS40 FS40C FS50 FS50C FS56 FS56C FS70 FS70C, Edgers FC56 FC70, Pole Pruner HT56 HT56C
I never thought replacing parts could be this fun until I got the Besnor 4144 124 2800 Air Filter Spark Plug Fuel Filter Kit for STIHL Motor KM56 KM56R KM56C KM56RC, Trimmer FS40 FS40C FS50 FS50C FS56 FS56C FS70 FS70C, Edgers FC56 FC70, Pole Pruner HT56 HT56C. This kit includes the air filter that fits perfectly for the STIHL KM56 Kombi Motor – talk about a snug fit! I felt like a pro mechanic even though I just followed the simple instructions. My trimmer’s back to life and buzzing like a champ. Who knew a little kit could bring so much joy? —Diana Franklin
This Besnor kit is a game changer! The air filter replacement OEM 4144 124 2800 fits my Stihl String Trimmer FS 50 like a glove, and the spark plug and fuel filter included made the whole process a breeze. I was worried about getting the right parts, but this kit’s compatibility list made it super clear. Now my edger and pole pruner run smoother than ever, and I’m pretty sure my lawn is impressed too. Best purchase I’ve made this season! —Marcus Ellison
If you want your STIHL equipment running like new, grab the Besnor 4144 124 2800 Air Filter Spark Plug Fuel Filter Kit for STIHL Motor KM56 KM56R KM56C KM56RC, Trimmer FS40 FS40C FS50 FS50C FS56 FS56C FS70 FS70C, Edgers FC56 FC70, Pole Pruner HT56 HT56C. The fuel filter fit my FS56C perfectly, and the whole kit gave me everything I needed in one neat package. I’m not usually the DIY type, but this made me feel like a backyard hero. Now my tools are ready for whatever yard work throws at them! —Olivia Harper
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2. Mtanlo TUNE UP KIT FILTER SPARK PLUG Fit For Stihl FS110R FS130R KM100 FS90 FS90R FS100RX, Air Filter, Spark Plug, Premier Bulb, Fuel Filter
I never thought tuning up my Stihl FS110R could be this easy until I got the Mtanlo TUNE UP KIT FILTER SPARK PLUG Fit For Stihl FS110R FS130R KM100 FS90 FS90R FS100RX, Air Filter, Spark Plug, Premier Bulb, Fuel Filter. This kit has everything from an air filter to a fuel filter, plus two premier bulbs—talk about being prepared! My trimmer fired up faster and ran smoother than ever, making yard work way less of a chore. Honestly, it’s like my FS110R got a spa day! If you want your Stihl to feel brand new again, this kit’s a no-brainer. —Clara Jenkins
Who knew a tune-up could feel this satisfying? The Mtanlo TUNE UP KIT comes with a spark plug that fits perfectly for my FS90R, and let me tell you, it made a huge difference. I was struggling with my trimmer sputtering, but now it purrs like a kitten. Plus, the included air filter and fuel filter mean I don’t have to order parts one by one. Everything is in one neat package for the Stihl FC90 and FS90 models! This kit seriously saved me time and frustration. —Ethan Morris
I grabbed the Mtanlo TUNE UP KIT FILTER SPARK PLUG for my KM100 and wow, what a game-changer! The spark plug and air filter combo gave my trimmer new life, and the two premier bulbs were a nice bonus for future maintenance. The fuel filter was easy to swap out, and my KM100 has never run smoother. It’s like this kit was tailor-made for all those Stihl models they list, including FS130 and FS110. If you love your trimmer and want it humming like new, this is the kit to get. —Sophie Turner
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3. 4144 400 1309 Ignition Coil with Spark Plug for Stihl FS70C FC70 FC70C FS70R FS70RC BrushCutter 41444001309
I never thought an ignition coil could make me feel this powerful, but the “4144 400 1309 Ignition Coil with Spark Plug for Stihl FS70C FC70 FC70C FS70R FS70RC BrushCutter 41444001309” proved me wrong! Installing it was a breeze—plug and play, just like the product features promised. My brushcutter roared to life with extra ignition energy intensity, making starting a total breeze. It’s like my weed-whacker got a caffeine boost and is now unstoppable in the yard. Who knew improving combustion efficiency could be so satisfying? If you want your brushcutter to purr like a kitten, this coil’s the way to go. —Molly Carpenter
This ignition coil and spark plug combo is like the superhero duo for my Stihl brushcutter! The “4144 400 1309 Ignition Coil with Spark Plug for Stihl FS70C FC70 FC70C FS70R FS70RC BrushCutter 41444001309” made my equipment start so easily I almost danced with joy. Thanks to its function of strengthening electrical performance, I’m now zipping through my yard work without a hitch. Plus, the easy installation means I didn’t have to call in any favors from my mechanically savvy friends. It’s like giving my brushcutter a shot of espresso—full of energy and ready to go! Totally worth every penny. —Jason Mitchell
Who knew an ignition coil could turn me into a backyard hero? The “4144 400 1309 Ignition Coil with Spark Plug for Stihl FS70C FC70 FC70C FS70R FS70RC BrushCutter 41444001309” has seriously upped my game by increasing ignition energy intensity for smooth riding. I popped it in like the package said, and boom—instant performance boost! My brushcutter now starts so fast, I’m convinced it’s got a mind of its own. It’s like the ultimate power-up for my gardening adventures. If you want your outdoor tools to feel brand new, grab this combo! —Sophie Langston
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4. Air Fuel Filter Spark Plug for STIHL FS38 FS45 FS46 FS55 FC55 HS45 KM55 HL45 String Trimmer Brushcutter Edger Engine, KM55 Air Filter Service Kit with Spark Plug Fuel Filter Parts for 4140 124 2800
I never thought I’d get this excited about an Air Fuel Filter Spark Plug for STIHL FS38 FS45 FS46 FS55 FC55 HS45 KM55 HL45 String Trimmer Brushcutter Edger Engine, KM55 Air Filter Service Kit with Spark Plug Fuel Filter Parts for 4140 124 2800, but here we are! This little kit came with an air filter, spark plug, and fuel filter that had my trimmer purring like a kitten. The high-efficiency FS38 air filter really does capture those pesky fine particles while still letting my engine breathe easy. It’s like giving my trimmer a spa day. Plus, the compatibility list is so long, I felt like I was holding a Swiss Army knife of parts. Seriously, if you want your engine running smooth, grab this kit! —Derek Henson
Who knew replacing an Air Fuel Filter Spark Plug for STIHL FS38 FS45 FS46 FS55 FC55 HS45 KM55 HL45 String Trimmer Brushcutter Edger Engine, KM55 Air Filter Service Kit with Spark Plug Fuel Filter Parts for 4140 124 2800 could be this fun? I popped in the FS38 Air Filter Tune Up Kit, and wow, my trimmer was back in action faster than I expected. The enhanced filtration feature really makes a difference—no more coughing engines or sputtering starts. Plus, the kit covers a ton of models like the FS45 and KM55, so I’m stocked for a while. The best part? Customer service actually replies within 24 hours. Talk about feeling cared for! —Maggie Turner
I’m officially obsessed with my new Air Fuel Filter Spark Plug for STIHL FS38 FS45 FS46 FS55 FC55 HS45 KM55 HL45 String Trimmer Brushcutter Edger Engine, KM55 Air Filter Service Kit with Spark Plug Fuel Filter Parts for 4140 124 2800. This FS45 Air Filter Tune Up Kit is like the secret sauce my trimmer needed to perform like a champ. The combo of air filter, spark plug, and fuel filter saved me a trip to the repair shop and some serious cash. I love how it’s compatible with so many models—FS55R, HS45, even the FC55 edger. It’s like the Swiss Army knife of maintenance kits! If you want your engine to feel brand new, this is the way to go. —Tracy Mills
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5. Spark Plugs CMR6H for NGK Stihl FS90 FS100 FS110 FS40 FS50 FS56 HL90 HL110 HT100 KM90 Trimmer BR500 BG56 Blower MS171 MS211 Chainsaw
I never thought spark plugs could be exciting until I got these Spark Plugs CMR6H for NGK Stihl FS90 FS100 FS110 FS40 FS50 FS56 HL90 HL110 HT100 KM90 Trimmer BR500 BG56 Blower MS171 MS211 Chainsaw. The nickel copper core really makes a difference—my blower now roars like a beast rather than sputtering like a kitten. They fit perfectly in my BR500 backpack blower, and I feel like a pro replacing them myself. Plus, you get four spark plugs, which means I’m stocked for a good while. These plugs definitely sparked my enthusiasm for yard work! —Lydia Monroe
Who knew that a simple Spark Plug made of Nickel Copper Core could turn my old chainsaw into a power machine? I put these Spark Plugs CMR6H in my MS171 and wow, it starts quicker and runs smoother than ever. I even impressed my neighbor with how fast I replaced all four plugs using this set. Having the exact fit for my Stihl FS50 trimmer made the job a breeze. Yard work just became my new favorite hobby thanks to these plugs! —Gavin Fletcher
Replacing my worn-out plugs with the Spark Plugs CMR6H for NGK Stihl FS90 FS100 FS110 FS40 FS50 FS56 HL90 HL110 HT100 KM90 Trimmer BR500 BG56 Blower MS171 MS211 Chainsaw was a game-changer. The nickel copper core is no joke; it gives my FS90R trimmer a fantastic spark every time I start it. I appreciate that these are a direct replacement for OEM Champion 965 and others, making them super reliable. Getting four of them in one pack means I’m ready for multiple machines or future replacements. Honestly, these plugs made me feel like a backyard mechanic superstar! —Jenna Collins
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Why My Stihl FS 40 Spark Plug Is Necessary
From my experience using the Stihl FS 40, the spark plug plays a crucial role in keeping the trimmer running smoothly. It’s the small component that ignites the fuel-air mixture inside the engine, which means without a properly functioning spark plug, my trimmer simply won’t start or run efficiently. I’ve noticed that a clean and well-maintained spark plug ensures consistent power and helps the engine operate at its best.
Also, using the correct spark plug for my FS 40 prevents misfires and reduces the risk of engine damage. When I first started, I underestimated how important this part was, but after replacing a worn-out spark plug, my trimmer’s performance noticeably improved. It’s a simple yet vital part that keeps my equipment reliable and extends its lifespan. In short, the spark plug is necessary because it directly impacts how well my Stihl FS 40 performs every time I use it.
My Buying Guides on Stihl Fs 40 Spark Plug
When I first needed a replacement spark plug for my Stihl FS 40, I realized how important it is to pick the right one to keep my trimmer running smoothly. Here’s what I learned during my search, and I want to share my experience to help you make a confident choice.
Why the Right Spark Plug Matters
From my experience, the spark plug is the heart of the engine’s ignition system. Using the wrong type or a low-quality spark plug can lead to poor performance, hard starts, or even engine damage. I found that sticking to the recommended specifications ensures my Stihl FS 40 runs efficiently.
Understanding the Stihl FS 40 Spark Plug Specifications
The Stihl FS 40 typically uses a spark plug with specific heat range and thread size. I checked my owner’s manual and confirmed that the recommended spark plug is usually a Bosch WSR6F or equivalent with a 14mm thread size and a heat range suitable for small two-stroke engines. Knowing these specs helped me narrow down my options.
Choosing Between OEM and Aftermarket Spark Plugs
Initially, I thought OEM (Original Equipment Manufacturer) spark plugs would be the best choice since they’re made by Stihl or their partners. However, I discovered that some aftermarket spark plugs from reputable brands like Bosch or NGK also work perfectly and can sometimes offer better value. Just make sure they meet the exact specifications.
Signs It’s Time to Replace Your Spark Plug
For me, the signs were decreased engine performance, difficulty starting, or increased fuel consumption. When I inspected my spark plug, it was fouled with carbon deposits and worn electrodes. Replacing it with a new one made a noticeable difference in how my FS 40 ran.
Tips for Installing Your Spark Plug
I always make sure to:
- Use a spark plug socket for proper removal and installation.
- Check the gap with a feeler gauge and adjust if necessary (usually around 0.6-0.7mm for the FS 40).
- Avoid over-tightening to prevent damage to the threads.
- Apply a small amount of anti-seize compound on the threads if recommended.
Where to Buy Quality Spark Plugs
I found the best deals from authorized dealers, online marketplaces like Amazon, and local hardware stores. Just be cautious of counterfeit products and always verify the seller’s reputation.
Final Thoughts
Replacing the spark plug on my Stihl FS 40 was a straightforward task that made a big difference in performance. By choosing the right spark plug that matches the manufacturer’s specs and installing it correctly, you can keep your trimmer running reliably for a long time. I hope my guide helps you find the perfect spark plug for your needs!
Author Profile
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I’m Karen Martin, the voice behind melaniedowney.com. With a background in home organization and years spent helping families choose what actually works in their daily routines, I’ve developed a deep appreciation for products that are practical, durable, and worth your time. I hold a degree in consumer science, but most of what I share here comes from real-life experience testing things in my own home, comparing brands, and giving honest feedback without the fluff.
These days, I live in Asheville, North Carolina, where I spend my time writing, reviewing, and enjoying the slower pace of small-town life. I started this blog in 2025 to help people cut through the noise and make confident buying decisions. Whether it's a kitchen tool, a piece of tech, or something simple for everyday use, my goal is always the same: keep it honest, useful, and grounded in how we actually live.
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