How to Replace String on Stihl Weed Eater? Easy DIY Beginner Tutorial

Introduction

If you own a Stihl weed eater, you already know these tools are built to tackle even the toughest overgrowth with ease. But like any outdoor power equipment, the cutting string is a consumable part that wears down over time from abrasion, impact with hard surfaces, and regular friction. Many homeowners assume replacing the string requires a trip to the repair shop and a hefty service fee, but the answer to How to Replace String on Stihl Weed Eater? is far simpler than you might think. This beginner-friendly DIY tutorial will walk you through every step of the process, no special tools or prior experience required. In just 10 to 15 minutes, you can have your Stihl running like new, and save $20 to $30 per replacement compared to professional service. Whether you have a gas-powered, cordless, or electric Stihl model, the core steps are nearly identical, and we’ll cover model-specific nuances throughout this guide.

Table of Contents

• Why Does Stihl Weed Eater String Wear Out So Fast?
• Tools and Materials You’ll Need for the Replacement
• Safety Precautions Before You Start
• Step 1: Disconnect the Power Source
• Step 2: Remove the Trimmer Head
• Step 3: Remove the Old, Worn-Out String
• Step 4: Prepare the New Replacement String
• Step 5: Wind the New String Correctly
• Step 6: Reattach the Trimmer Head
• Step 7: Test the Weed Eater
• Common Mistakes to Avoid When Replacing Stihl String
• Stihl Weed Eater String Type Comparison
• Tips to Extend Your Stihl Weed Eater String’s Lifespan
• Frequently Asked Questions
• Conclusion

Why Does Stihl Weed Eater String Wear Out So Fast?

Even high-quality Stihl string is designed to be a sacrificial wear part, meaning it’s intended to wear down before more expensive components like the trimmer head, drive shaft, or engine. Several factors accelerate how quickly your string wears out:

• Abrasion from cutting material: Every time the string slices through grass, weeds, or small brush, it rubs against plant fibers, dirt, and small debris that wear down the outer layer of the plastic string. Thick, woody weeds and brush wear down string far faster than soft grass.
• Impact with hard surfaces: Hitting rocks, concrete curbs, fence posts, or metal edging chips and breaks string instantly. Even small, repeated impacts with gravel or dirt clods will shorten your string’s lifespan significantly.
• Incorrect string type or diameter: Using string that’s too thin for your model or use case will break easily under heavy load, while string that’s too thick puts excess strain on the engine and wears down faster from increased friction.
• Improper winding: If string is wound loosely or overlapping on the spool, it will tangle, jam, and break far more often than neatly wound string.
• Environmental exposure: Prolonged exposure to direct sunlight degrades the plastic in the string, making it brittle and prone to breaking. Storing your weed eater in a hot garage or shed can also accelerate this wear.

Understanding these wear factors will help you extend your string’s lifespan, and recognize when it’s time for a replacement.

Tools and Materials You’ll Need for the Replacement

One of the best parts of replacing your Stihl weed eater string yourself is that you don’t need any specialized, expensive tools. Most of the items you’ll need are already lying around your house, and the rest are inexpensive to pick up at any hardware store. Here’s what you’ll need:

• Replacement Stihl-compatible cutting string (correct diameter for your model, most residential Stihl weed eaters use .080 inch / 2.0mm string, commercial models use .095 inch / 2.4mm or .105 inch / 2.7mm)
• Phillips head screwdriver (some Stihl models use a Torx bit, so check your owner’s manual if a Phillips doesn’t fit)
• Work gloves (to protect your hands from sharp string edges)
• Safety glasses (to protect your eyes from flying debris when testing the weed eater)
• Wire cutters (to cut the string to the correct length)
• Clean rag (to wipe away grass clippings and debris from the trimmer head)
• Optional: String winder tool (makes winding string faster and tighter, especially for beginners)
• Optional: Penetrating oil (if the trimmer head is stuck and won’t loosen)

If you don’t want to wind the string yourself, you can also purchase pre-wound Stihl replacement spools that are ready to install out of the box. These are a great option for beginners or if you need to replace the string quickly.

Safety Precautions Before You Start

Before you start working on your Stihl weed eater, taking a few basic safety steps will prevent accidental injury and damage to your tool. These precautions take less than a minute, but they’re critical for a safe, hassle-free replacement:

• Fully disconnect the power source: For gas-powered Stihl models, pull the spark plug boot off the spark plug to completely disable the engine (don’t just turn the ignition switch off, as the engine could accidentally start). For cordless models, remove the battery pack fully from the tool. For electric models, unplug the power cord from the outlet. Never work on the trimmer head while the power source is connected.
• Wear protective gear: Always wear safety glasses to protect your eyes from sharp string ends and flying debris, and work gloves to avoid cuts from the sharp edges of cutting string.
• Work in a safe area: Clear the area of bystanders, pets, and tripping hazards before you start. If you’re working on a gas model, make sure you’re in a well-ventilated area to avoid inhaling fumes.
• Let a hot engine cool: If you’ve just used your gas-powered Stihl, wait at least 15 minutes for the engine and exhaust to cool down before touching the trimmer head to avoid burns.

Step 1: Disconnect the Power Source

As mentioned in the safety section, the first and most important step is to fully disable your weed eater to avoid accidental startup. For gas models, locate the spark plug on the side of the engine, grip the rubber boot on the end of the spark plug wire, and pull it straight off the spark plug. Set the wire aside so it doesn’t accidentally reconnect while you’re working. For cordless models, press the release button on the battery pack and slide it out of the tool’s battery bay. For electric models, unplug the power cord from the wall outlet and set it aside.

Once the power source is disconnected, you can safely work on the trimmer head without risk of the string spinning unexpectedly.

Step 2: Remove the Trimmer Head

Stihl makes two main types of trimmer heads: bump feed (auto-feed) heads, which automatically advance the string when you tap the bottom of the head on the ground, and fixed line (manual feed) heads, which require you to manually advance the string when it wears down. The process for removing the head is nearly identical for both types, with minor differences:

Removing a Bump Feed Trimmer Head

Most Stihl bump feed heads are secured with a retaining nut on the bottom of the head, or a quick-release lever for tool-free removal. First, turn the weed eater upside down so the trimmer head is facing up. If your model has a quick-release lever, flip the lever to the “unlock” position, then pull the head straight off the drive shaft. If your model uses a retaining nut, use your Phillips screwdriver to loosen the nut by turning it counterclockwise (left). Once the nut is loose, pull the head straight off the drive shaft. Don’t twist the head as you pull it, as this can damage the drive shaft splines.

Removing a Fixed Line Trimmer Head

Fixed line heads are secured the same way as bump feed heads, either with a retaining nut or quick-release lever. Some models have a small locking button on the side of the head that you need to press down before you can loosen the nut. Once the nut is loose or the lever is flipped, pull the head straight off the drive shaft. The spool inside the fixed line head will usually stay attached to the head, unlike some bump feed models where the spool is separate.

Step 3: Remove the Old, Worn-Out String

Once the trimmer head is removed, you can take out the old string. For bump feed models, the spool is usually a separate piece that sits inside the head. Pull the spool out of the head, then unwind and remove all the old string from the spool. For fixed line models, the spool is built into the head, so you’ll need to unwind the old string from the spool directly.

If the old string is stuck or frayed, use needle-nose pliers to pull it out of the spool eyelets. Once all the old string is removed, use your clean rag to wipe away any grass clippings, dirt, or debris from the inside of the trimmer head and the spool. This step is important, as built-up debris can cause the new string to jam or not feed correctly. Inspect the spool and trimmer head for cracks or damage while you’re cleaning them—if you notice any broken parts, replace the entire head before installing new string.

Step 4: Prepare the New Replacement String

Cutting the new string to the correct length is critical for proper feeding and cutting performance. The length you need depends on your trimmer head type:

• Bump feed heads: Cut two equal lengths of string, each 10 to 12 feet long. This gives you enough string to wind tightly on the spool and leave enough excess to feed through the eyelets.
• Fixed line heads: Cut two equal lengths of string, each 8 to 10 feet long. Fixed line heads don’t require as much excess string, as the lines are fed manually.

Use your wire cutters to cut the string straight across, not at an angle, to avoid frayed ends. If the ends of the string are frayed after cutting, you can lightly melt them with a lighter to seal the plastic and prevent further fraying. Hold the end of the string over the flame for 1 to 2 seconds, then blow it out to cool. Be careful not to melt too much of the string, as this can make the end too thick to fit through the spool eyelets.

Step 5: Wind the New String Correctly

Winding the string in the correct direction and tightly enough is the most important step to ensure your string feeds properly and doesn’t tangle. Almost all Stihl spools have a small arrow printed on the top that indicates the correct winding direction—always wind the string in the direction the arrow points. Winding in the opposite direction will cause the string to jam and not feed when you’re using the weed eater.

Winding String for Bump Feed Spools

Hold the spool in one hand, with the arrow facing you. Insert the end of the first string into the eyelet on the side of the spool, then wind the string tightly around the spool in the direction of the arrow. Wind the string in neat, even rows, don’t overlap the string or leave gaps, as this will cause tangles. Leave 6 to 8 inches of string sticking out of the eyelet when you’re done winding. Repeat this process with the second string, winding it in the same direction as the first, and leaving the same length of string sticking out of the opposite eyelet.

Winding String for Fixed Line Spools

Fixed line spools have eyelets on opposite sides of the spool, and you need to wind the two lines in opposite directions to prevent tangling. Insert the end of the first string into the eyelet on one side of the spool, wind it tightly in the direction of the arrow, and leave 8 to 10 inches of string sticking out of the bottom of the spool (not the eyelet). Repeat with the second string on the opposite side, winding it in the opposite direction of the first line, and leaving the same length of string sticking out of the bottom of the spool. Make sure the two lines don’t cross over each other as you wind, as this will cause jams.

Step 6: Reattach the Trimmer Head

Once the new string is wound correctly, it’s time to put the trimmer head back on the weed eater. First, make sure the loose ends of the string are seated in the small grooves on the bottom of the trimmer head (for bump feed) or sticking out the bottom of the head (for fixed line). Align the spool with the slots in the trimmer head, then push the head straight onto the drive shaft until it clicks into place. For models with a retaining nut, tighten the nut by turning it clockwise (right) until it’s snug—don’t overtighten, as this can strip the threads on the drive shaft and make it hard to remove the head next time. For models with a quick-release lever, flip the lever back to the “lock” position to secure the head.

If your model has a bump knob (the rubber button on the bottom of the head), make sure it moves up and down freely after you reattach the head, as a stuck bump knob will prevent the string from feeding.

Step 7: Test the Weed Eater

Now it’s time to test your work. First, reconnect the power source: push the spark plug boot back onto the spark plug for gas models, slide the battery back into the bay for cordless models, or plug the electric cord back into the outlet. Put on your safety glasses, then start the weed eater according to the manufacturer’s instructions.

Let the weed eater idle for 30 seconds to make sure it runs smoothly. If you have a bump feed model, tap the bottom of the trimmer head on the ground 2 to 3 times to advance the string. Check that both lines extend to the correct cutting width (usually 16 to 18 inches for residential Stihl models). If the lines are too short, tap the bump knob a few more times to advance them. If they don’t advance at all, turn off the weed eater, disconnect the power, and check that you wound the string in the correct direction and that there are no tangles inside the head.

Once the string is extended to the correct length, test the cutting power by trimming a small patch of grass or weeds. If the string cuts cleanly and doesn’t break immediately, you’ve successfully replaced the string. If the string breaks right away, check that it’s wound tightly and not overlapping on the spool, and that you’re using the correct string diameter for your model.

Common Mistakes to Avoid When Replacing Stihl String

Even experienced DIYers make these common mistakes when replacing Stihl weed eater string. Avoiding them will save you time, frustration, and damage to your tool:

• Using the wrong string diameter: Using string that’s too thick will overload the engine and break the string faster, while string that’s too thin will break easily under heavy load. Always check your owner’s manual for the recommended diameter for your specific model.
• Winding the string in the wrong direction: This is the most common cause of string feeding issues. Always follow the arrow on the spool when winding.
• Overlapping or loosely winding the string: Overlapping string causes tangles and jams, while loose winding leads to uneven feeding and frequent breakage. Wind the string tightly in neat, even rows.
• Overtightening the trimmer head: Overtightening the retaining nut strips the threads on the drive shaft, making it almost impossible to remove the head for future replacements. Tighten the nut until it’s snug, then give it a quarter turn more—no need for force.
• Skipping the cleaning step: Failing to clean grass clippings and debris out of the trimmer head before installing new string leads to jams and poor feeding performance. Always wipe out the head before reinstalling it.
• Not disconnecting the power source: Failing to disconnect the spark plug, battery, or power cord can lead to accidental startup, which can cause serious injury. Always disable the power before working on the trimmer head.

Stihl Weed Eater String Type Comparison

Not all cutting string is created equal, and choosing the right type for your use case will improve cutting performance and extend the string’s lifespan. Stihl and most third-party brands offer several different string profiles, each designed for specific tasks. Use the comparison table below to choose the best string for your needs:

For most homeowners, a square or star-shaped string offers the best balance of durability and cutting power for everyday use. If you only trim light grass occasionally, standard round string is a cost-effective option. For commercial users or anyone cutting heavy brush, twisted heavy-duty string is the best choice for maximum durability.

Tips to Extend Your Stihl Weed Eater String’s Lifespan

Replacing your Stihl weed eater string is easy, but extending its lifespan will save you even more time and money in the long run. Follow these tips to get the most out of every string replacement:

• Use the correct string diameter for your use case: If you only trim light grass, use a thinner .080 inch string, which is more flexible and less likely to break. For thick weeds and brush, use a thicker .095 inch string for added durability.
• Avoid hard surfaces: Try to avoid hitting rocks, concrete, metal edging, and fence posts with your string. If you’re trimming near these surfaces, adjust the cutting height of your weed eater or use a guard to protect the string.
• Clean the string and head after each use: Wipe the string down with a rag after each use to remove grass sap, dirt, and debris that can degrade the plastic over time. Clean out the trimmer head to remove built-up grass clippings that can cause jams.
• Store your weed eater properly: Store your Stihl in a cool, dry, shaded area out of direct sunlight. UV exposure from the sun degrades the plastic in the string, making it brittle and prone to breaking. If you’re storing your weed eater for the winter, remove the string entirely to prevent it from becoming brittle.
• Don’t overload your weed eater: Trying to cut thick, woody brush that’s thicker than your string’s recommended capacity will break the string immediately and damage the engine. Use a chainsaw or brush cutter for material that’s too thick for your weed eater.
• Inspect the string before each use: Check for fraying, chipping, or wear before you start trimming. If you notice any damage, replace the string before you start working to avoid breakage mid-job.

Frequently Asked Questions

Here are answers to the most common questions homeowners have about replacing Stihl weed eater string:

How often should I replace the string on my Stihl weed eater?

It depends on how frequently you use your weed eater and what you’re cutting. For light residential use (trimming grass 1 to 2 times per week), you’ll need to replace the string every 1 to 2 months. For heavier use (cutting thick weeds and brush 3 or more times per week), you may need to replace it every 2 to 4 weeks. If you notice the string is frayed, chipped, or not cutting effectively, it’s time to replace it regardless of how long it’s been installed.

Can I use third-party replacement string on my Stihl weed eater?

Yes, you can use high-quality third-party replacement string as long as it matches the diameter recommended for your Stihl model. Avoid cheap, low-quality string, as it frays easily, breaks frequently, and can damage your trimmer head. Stihl’s own string is formulated to match their trimmer heads for optimal performance, but reputable third-party brands work just as well for most users.

Why is my new Stihl string not feeding after replacement?

The most common cause is that you wound the string in the wrong direction. Check the arrow on the spool and make sure you wound the string in the direction the arrow points. Other common causes include overlapping string on the spool, string that’s too long and tangled inside the head, or debris blocking the string eyelets. Clean out the head and rewind the string correctly to fix the issue.

What string diameter should I use for my Stihl weed eater?

Most residential Stihl weed eaters use .080 inch (2.0mm) diameter string, while commercial-grade models use .095 inch (2.4mm) or .105 inch (2.7mm) string for heavy-duty cutting. Check your owner’s manual for the exact recommended diameter for your specific model, as using a thicker or thinner string than specified can damage your tool and reduce performance.

Is it better to buy a pre-wound spool or wind the string myself?

Pre-wound spools are more convenient and save time, especially for beginners or if you need to replace the string quickly. They are also pre-measured to the correct length, so you don’t have to cut the string yourself. Winding the string yourself is cheaper (you can buy a bulk roll of string for the price of 2 to 3 pre-wound spools) and gives you more control over the winding tightness, which can improve feeding performance. Either option works well, so choose what fits your budget and skill level.

Can I use a Stihl weed eater with only one line of string if it’s a dual-line model?

Technically you can, but it’s not recommended. Dual-line models are designed to use two lines for balanced cutting and reduced vibration. Using only one line will cause uneven cutting, excessive vibration, and increased wear on the trimmer head and engine. If you’re in a pinch and only have one line, you can use it temporarily, but replace it with two lines as soon as possible.

Conclusion

Now that you know the answer to How to Replace String on Stihl Weed Eater?, you can tackle this simple maintenance task yourself with confidence. Replacing your Stihl’s cutting string is a quick, low-cost DIY project that saves you money on professional service and keeps your tool running at peak performance. By following the step-by-step guide above, avoiding common mistakes, and using the right string for your use case, you’ll have your weed eater cutting like new in no time. Regular maintenance like string replacement also extends the overall lifespan of your Stihl, so you can enjoy reliable performance for years to come. Next time your string wears out, skip the repair shop and try replacing it yourself—you’ll be surprised how easy it is!