Stihl String Trimmer Spark Plug Parts

Stihl String Trimmer Spark Plug Replacement Parts

A fouled or worn spark plug is one of the quickest fixes for a Stihl string trimmer that won't start or runs rough. Stihl trimmers use specific heat-range spark plugs — using the wrong type can cause hard starting and poor performance. The correct OEM spark plug ensures reliable ignition in all weather conditions.

If your Stihl FS45, FS55, FS90, or FS111 trimmer is difficult to start or misfiring during operation, the spark plug is the first thing to check before moving on to the carburetor or fuel system. Replace it annually before the mowing season and keep a spare on hand.

• Trimmer won't start: Fouled plug from old fuel or incorrect fuel mix
• Hard starting after sitting: Worn plug electrode gap or carbon buildup
• Runs rough or surges: Heat range incorrect or spark timing issue
• Black soot visible on plug: Running too rich; check carburetor and air filter
• White or tan residue on plug: Running too lean; carburetor adjustment needed

Find your Stihl model number on the trimmer frame and use our model lookup tool to identify the exact spark plug specification for your trimmer. Stihl OEM plugs maintain proper electrode gap and heat range for dependable starting season after season.

Stihl String Trimmer Spark Plug FAQs

What is the correct spark plug for my Stihl string trimmer?

Stihl FS-series trimmers typically use Champion RJ19LM or equivalent NGK spark plugs, but the exact type varies by model year and engine displacement. The correct plug is printed on the Stihl parts diagram or stamped in the operator manual. Using the wrong heat range can cause hard starting or engine damage. Enter your trimmer's model number at the top of this page to confirm the OEM spark plug specification.

How often should I replace the spark plug in my Stihl trimmer?

Replace the spark plug at the start of each mowing season — typically spring for most users. If you use your trimmer year-round, replace it every 100 operating hours or annually, whichever comes first. Inspect it monthly during heavy use. A worn or fouled plug is the #1 reason Stihl trimmers are hard to start.

My Stihl trimmer starts but runs rough. Is it the spark plug?

Rough running can be the spark plug, but check the air filter and fuel mixture first. If the plug electrode has a black, sooty coating, the fuel mix is too rich — verify your two-stroke ratio (usually 40:1 or 50:1 depending on model). If the plug looks clean but the trimmer still runs rough, the carburetor may need adjustment or cleaning. A new OEM spark plug is still worth trying since old fuel can foul even a good plug.

Can I use an aftermarket spark plug instead of OEM Stihl?

Yes, Champion and NGK aftermarket plugs often work, but Stihl OEM plugs are engineered for your specific model's ignition timing and compression ratio. Aftermarket plugs in the wrong heat range can cause starting difficulty or poor performance. For reliability, especially on older Stihl models, stick with the OEM specification. Aftermarket plugs are cheaper, but a $3 to $5 OEM plug is worth the certainty.

Order Stihl String Trimmer Spark Plug Parts Online

Ensure your Stihl string trimmer operates at peak efficiency with our genuine spark plug replacements. Finding the right spark plug is key for maintaining your equipment's reliability and efficiency. Our easy-to-use online platform allows you to search using model or part numbers, ensuring you find the exact Stihl spark plug you need. Benefit from our same-day shipping, so you can get your trimmer back in action quickly. Plus, our No-Hassle 365-Day Returns and Price Match Guarantee help you order with confidence. If your string trimmer won't start, a faulty spark plug might be the cause; replacing it can resolve the issue. Visit our Stihl String Trimmer Spark Plug Parts page to order now. For more repair solutions, browse our String Trimmer Repair Help section for troubleshooting tips and guides.

Find the Model Number on Your Stihl String Trimmer

Stihl prints the model number on the main housing near the engine, and some models also have it on a label along the shaft. Look for a label or plate showing the FS series designation and related identification details. Use the complete model number, including any letters or numbers that follow it, rather than relying on the spark plug number. Punch it into the search bar to sort the catalog down to your model's parts. This filters the full Stihl string trimmer parts selection, not just spark plugs, so you can check compatibility across the entire unit. That means fewer wrong orders and a faster repair.