Introduction
Stihl is one of the most trusted brands in outdoor power equipment, and their string trimmers (commonly called weed eaters) are a staple for homeowners and professional landscapers alike. But even the most durable Stihl trimmer is useless if the cutting line is broken, frayed, or completely worn out. If you’ve ever found yourself staring at a dead trimmer mid-yard project, you’ve probably asked yourself: How to Put String in Stihl Weed Eater?
The good news is that replacing Stihl trimmer line is a simple, 5 to 10 minute task that requires no special tools or mechanical experience. Stihl uses two primary head designs for their trimmers: the AutoCut bump-feed head and the FixCut fixed-length head, each with a slightly different loading process. This in-depth guide covers both head types step-by-step, includes pro tips for long-lasting performance, a comparison of the two head styles, and answers to common questions to ensure you get the job done right the first time.
Table of Contents
- Why Knowing How to Put String in Stihl Weed Eater Matters
- Understanding Stihl’s Two Most Common Trimmer Head Types
- AutoCut Trimmer Heads: How They Work
- FixCut Trimmer Heads: How They Work
- Tools and Materials You’ll Need for String Replacement
- Step-by-Step: How to Put String in Stihl Weed Eater with an AutoCut Head
- Step-by-Step: How to Put String in Stihl Weed Eater with a FixCut Head
- Key Differences Between AutoCut and FixCut String Loading
- Pro Tips for Easy, Long-Lasting String Replacement
- Common Mistakes to Avoid When Replacing Stihl Trimmer Line
- Frequently Asked Questions About Loading Stihl Weed Eater String
- Conclusion
Why Knowing How to Put String in Stihl Weed Eater Matters
A broken or worn trimmer line renders your weed eater completely useless: you can’t edge grass along sidewalks, cut down overgrown weeds, or clear brush around your property. For many people, the default response to a broken line is to take the trimmer to a small engine repair shop, where a professional will charge $20 to $30 per replacement, or worse, buy an entirely new weed eater for hundreds of dollars.
Learning How to Put String in Stihl Weed Eater? eliminates these costs entirely, and takes less time than a trip to the repair shop. Proper line loading also prevents damage to your trimmer’s head, spindle, and engine: running a trimmer with no line can wear down bearings and cause excessive vibration that leads to costly repairs down the line. Even for beginners, the process is intuitive, and with this guide, you’ll be able to replace your line in minutes, no prior experience required.
Understanding Stihl’s Two Most Common Trimmer Head Types
Before you start the replacement process, it’s critical to identify which type of head your Stihl weed eater uses, as the loading process varies significantly between the two. Stihl’s most popular residential and professional trimmers use either an AutoCut bump-feed head or a FixCut fixed-length head. Both hold nylon trimmer line, but their mechanisms for feeding and securing line are designed for different use cases.
AutoCut Trimmer Heads: How They Work
AutoCut heads are the standard on most residential Stihl trimmers, including models like the FS 38, FS 40, and FS 56. They feature a bump-feed mechanism: while the trimmer is running at full throttle, bumping the bottom of the head on the ground releases 2 to 3 inches of new line automatically. Line is stored on a removable plastic spool inside the head, and is wound loosely to allow the bump mechanism to pull line out smoothly. AutoCut heads are ideal for casual to moderate use, such as weekly lawn maintenance and light weed trimming, and are extremely easy to load, even for first-time users.
FixCut Trimmer Heads: How They Work
FixCut heads are designed for professional-grade Stihl trimmers, including the FS 90 R, FS 94 R, and other heavy-duty models. Unlike AutoCut heads, they do not have a bump-feed mechanism. Instead, line length is either fixed, or manually adjusted via a small knob on the side of the head. FixCut heads hold more line than AutoCut models, and are built to withstand heavy use, such as daily commercial landscaping, thick brush clearing, and cutting overgrown woody vegetation. The line is wound tightly around the spool, with the ends secured with knots to prevent unraveling during use. While the loading process is slightly more involved than AutoCut, it’s still straightforward for most users.
Tools and Materials You’ll Need for String Replacement
One of the best parts of replacing Stihl trimmer line is that you don’t need any specialized tools. All the items you need are likely already in your garage:
- Replacement Stihl trimmer line: Make sure to purchase line with the correct diameter for your model. Most residential trimmers use .080 inch diameter line, while professional models use .095 or .105 inch line. You can find the recommended diameter in your user manual, or by measuring the diameter of your old line with a caliper or ruler.
- Sharp scissors or dedicated trimmer line cutter: To cut the line to the correct length cleanly, without fraying.
- Soft cloth or rag: To wipe away grass, dirt, and debris from the head before disassembly.
- Small flathead screwdriver: Optional, for prying off stuck spool retention clips.
- Adjustable wrench or socket set: Required for most FixCut heads, which use a nut to secure the spool (check your manual for the correct size, usually 10mm or 13mm).
- Work gloves: To protect your hands from sharp, frayed line edges.
If you have a gas-powered Stihl trimmer, make sure the engine is fully cool before starting maintenance to avoid burns from the hot muffler or engine block.
Step-by-Step: How to Put String in Stihl Weed Eater with an AutoCut Head
Follow these steps to load new line into your AutoCut head, and you’ll have your trimmer running in minutes:
Step 1: Prepare Your Weed Eater for Maintenance
First, turn off your trimmer and disconnect the spark plug wire (for gas models) or remove the battery (for battery-powered models) to prevent accidental startup. Lay the trimmer on a flat surface with the head facing up. Wipe away all grass, dirt, and debris from the head with your rag, so no foreign material gets inside the spool when you load new line. This simple step prevents jams and ensures smooth line feeding later.
Step 2: Remove the Old Spool and Remaining String
Locate the spool retention clip or nut on the bottom of the AutoCut head. Most residential AutoCut heads use a small plastic clip: pry it off gently with your flathead screwdriver. Larger models may use a plastic nut that you turn counterclockwise to remove. Once the clip or nut is off, pull the old spool straight out of the head. Pull off any remaining old line from the spool and discard it. Inspect the spool for cracks or excessive wear; if it’s damaged, replace it with a new OEM Stihl spool for best performance. (See Also:How To Remove Weed Eater String)
Step 3: Measure and Cut Your New Trimmer Line
Take your new trimmer line and cut two equal lengths. For most residential AutoCut heads, 10 to 12 feet of total line (5 to 6 feet per side) is the correct length. Larger professional AutoCut heads may require 15 to 20 feet total. If you don’t have your user manual handy, 12 feet total is a safe starting point for most models. Cut the line with your scissors or line cutter, making sure the ends are clean and straight, with no fraying.
Step 4: Load the New String into the AutoCut Spool
Take one length of line and insert one end into the small hole in the center of the spool. Push the line through until it comes out the opposite side of the center hole. Now, wind the line around the spool in the direction indicated by the arrow printed on the top of the spool (this step is critical: winding the line backwards will prevent the bump feed from working). Wind the line neatly, overlapping each layer slightly to avoid gaps, and leave about 6 inches of line sticking out of the center hole on one side. Repeat this process with the second length of line on the opposite side of the spool, making sure both ends are the same length. Do not wind the line too tight: loose winding allows the bump mechanism to pull line out smoothly, while tight winding will cause jams.
Step 5: Reinstall the Spool and Test the Head
Align the small tabs on the spool with the slots inside the head, then push the spool straight in until it clicks into place. Reattach the retention clip or nut, turning it clockwise to tighten if you’re using a nut. Reconnect the spark plug wire or battery. Start the trimmer and let it idle for a few seconds, then bump the head on the ground 2 to 3 times. You should see 2 to 3 inches of line extend from each side with each bump. If the line doesn’t feed, turn off the trimmer, remove the spool, and confirm you wound the line in the correct direction. If the line feeds too much or tangles, rewind it more loosely. You’ve now mastered How to Put String in Stihl Weed Eater? with an AutoCut head.
Step-by-Step: How to Put String in Stihl Weed Eater with a FixCut Head
FixCut heads follow a similar overall process, but have a few key differences in how line is inserted and secured. Follow these steps for your FixCut model:
Step 1: Prep the FixCut Head for Disassembly
As with AutoCut heads, start by turning off the trimmer, disconnecting the spark plug wire or removing the battery, and wiping the head clean of all debris. For gas models, confirm the engine is fully cool to avoid burns. FixCut heads are secured with a larger nut on the bottom of the head, rather than a small plastic clip. Use your adjustable wrench to loosen the nut (turn counterclockwise) – some models have a lock washer under the nut that you’ll need to remove as well.
Step 2: Remove the FixCut Spool and Clear Old Line
Once the nut and lock washer are removed, pull the spool straight out of the head. Remove all remaining old line from the spool, and inspect it for cracks or wear. Replace it with a new OEM Stihl FixCut spool if needed. Use your rag to clean out the line outlet holes on the sides of the head, removing any built-up grass, dirt, or line residue that could cause jams with new line.
Step 3: Cut and Feed New Line into the FixCut Head
Cut two equal lengths of line, 15 to 20 feet total (7.5 to 10 feet per side) for most FixCut models, as they hold more line for heavy use. Take one length of line and insert one end into the side outlet hole on the head (unlike AutoCut heads, FixCut heads feed line from side holes, not the center of the spool). Push the line through the outlet hole until it comes out the opposite side of the head, near the center where the spool sits.
Step 4: Wind the Line Correctly for FixCut Operation
Take the end of the line sticking out of the outlet hole, and wind it tightly around the spool in the direction of the arrow printed on the spool (again, winding backwards will cause the line to unravel immediately). Wind the line neatly, overlapping each layer to avoid gaps, until you have about 6 inches of line left on that side. Tie a firm overhand knot in the end of the line to secure it to the spool, so it doesn’t unwind during use. Repeat this process with the second length of line on the opposite side of the head: insert into the opposite outlet hole, wind tightly, and tie a secure knot in the end. Note that FixCut line must be wound much tighter than AutoCut line, as there is no bump feed to pull it out, so tension keeps the line from unraveling.
Step 5: Reassemble and Test the FixCut Head
Align the tabs on the spool with the slots in the head, then push the spool in until it is fully seated. Reattach the lock washer and nut, tightening the nut firmly with your wrench to secure the spool in place. Reconnect the spark plug wire or battery, and start the trimmer. Unlike AutoCut heads, FixCut heads do not have a bump feed, so you may need to use the adjustment knob on the side of the head (if your model has one) to extend the line to your desired length. Test the head by throttling the trimmer a few times: the line should stay securely in the outlet holes and not unravel. If it does, turn off the trimmer, remove the spool, rewind the line tighter, and tie more secure knots. You’ve now learned How to Put String in Stihl Weed Eater? with a FixCut head.
Key Differences Between AutoCut and FixCut String Loading
While both head types follow a similar general process of removing the old spool, measuring line, winding, and reinstalling, there are critical differences that make each process unique. The table below breaks down the core differences to help you quickly reference the right steps for your model: (See Also:How Fast Does A Weed Eater Spin)
| Feature | AutoCut Head | FixCut Head |
|---|---|---|
| Line Feeding Mechanism | Bump feed: line extends automatically when you bump the head on the ground while the trimmer is running | Manual feed: line length is fixed or adjusted via a knob on the head, no bump feed function |
| Line Winding Tension | Wound loosely, following the arrow on the spool, to allow smooth bump feeding | Wound tightly, following the arrow on the spool, with knots securing the ends to prevent unraveling |
| Recommended Total Line Length | 10–12 feet total (5–6 feet per side) for most residential models | 15–20 feet total (7.5–10 feet per side) for professional heavy-duty models |
| Line Insertion Point | Inserted into the center hole of the spool, then wound around the spool | Inserted into the side outlet holes of the head, then wound around the spool |
| Ideal Use Case | Residential lawn care, light to moderate grass and weed trimming | Commercial landscaping, heavy brush clearing, frequent daily use |
| Ease of Replacement | Very easy, no special tools required, takes 5 minutes or less | Slightly more involved, may require a wrench for the spool nut, takes 5–10 minutes |
If you’re still unsure which head you have, check the bottom of the head: AutoCut models have a small rubber bump button, while FixCut models have a small adjustment knob or no button at all. You can also confirm your head type by looking up your trimmer’s model number in the Stihl user manual or on the Stihl website.
Pro Tips for Easy, Long-Lasting String Replacement
Follow these tips to make line replacement even faster, and extend the life of your trimmer line and head:
- Always use Stihl OEM trimmer line or a high-quality aftermarket line rated for your trimmer’s power. Cheap, thin line will break constantly even if loaded correctly, and can damage the head or put excess strain on the engine.
- Wind the line neatly without gaps between layers, as gaps can cause tangles and jams in the head.
- For AutoCut heads, never wind the line tighter than a loose, even coil. Tight winding will block the bump feed mechanism and cause line jams.
- For FixCut heads, always tie a secure overhand knot in the end of each line after winding to prevent unraveling during use.
- Store extra trimmer line in a cool, dry place out of direct sunlight. UV exposure makes nylon line brittle and prone to breaking.
- Clean the head and spool every time you replace line to remove built-up grass, dirt, and line residue that can cause feeding issues.
- Keep a pre-loaded spare spool on hand for frequent use: you can swap out a broken spool in seconds without having to wind new line mid-job.
- If you struggle to get line to seat properly in the spool, use a tiny amount of silicone spray on the line to reduce friction. Avoid grease or oil, as it attracts dirt and causes jams.
Common Mistakes to Avoid When Replacing Stihl Trimmer Line
Avoid these common errors to ensure your line loads correctly and lasts as long as possible:
- Winding the line in the wrong direction: This is the most frequent mistake users make. If you wind the line backwards, AutoCut bump feeds will not work, and FixCut line will unravel immediately. Always follow the arrow printed on the spool.
- Using the wrong line diameter: Line that is too thin will break constantly, while line that is too thick will jam the head and overload the engine. Always use the diameter recommended for your specific model.
- Winding AutoCut line too tight or FixCut line too loose: Tight winding on AutoCut heads prevents bump feeding, while loose winding on FixCut heads causes the line to unravel during use.
- Skipping safety disconnection: Always disconnect the spark plug wire or remove the battery before working on the head. Accidental startup can cause serious injury.
- Failing to secure FixCut line ends with knots: Without knots, FixCut line will unwind from the spool as soon as you start trimming, leaving you with no cutting line.
- Overfilling the spool: Winding too much line will cause the spool to bulge, jamming the head and preventing it from seating properly. Stick to the recommended line lengths for your head type.
- Using grease or oil on the line or spool: Lubricants attract dirt and grass clippings, which cause jams and feeding issues. Only use sparingly applied silicone spray if needed.
Frequently Asked Questions About Loading Stihl Weed Eater String
How often do I need to replace the string on my Stihl weed eater?
The replacement frequency depends on how often you use the trimmer and what you’re cutting. For light residential use (trimming grass around sidewalks and flower beds once a week), you’ll need to replace the line every 1 to 2 months. For heavy commercial use (clearing thick brush and weeds daily), you may need to replace it weekly. You’ll know it’s time for a replacement when the line is frayed, worn down to less than 3 inches long, or breaks constantly even when bump fed.
Can I use aftermarket trimmer line instead of Stihl OEM line?
Yes, as long as the aftermarket line is the correct diameter for your model and rated for your trimmer’s power output. Many high-quality aftermarket lines perform just as well as OEM Stihl line, and are more affordable. Avoid cheap, low-quality line, as it breaks easily and can damage your head.
Why won’t my AutoCut head feed line after I loaded new string?
This is almost always caused by winding the line in the wrong direction, or winding it too tight. Turn off the trimmer, remove the spool, and confirm the line is wound in the direction of the arrow on the spool. If it’s wound correctly, rewind it more loosely, making sure there are no gaps between layers of line.
Why does my FixCut line keep unraveling when I use the trimmer?
This happens when you didn’t tie a secure knot in the end of the line after winding, or didn’t wind the line tightly enough. Turn off the trimmer, remove the spool, rewind the line tightly, and tie a firm overhand knot in the end of each line to secure it to the spool. (See Also:How To String Homelite Weed Eater)
Can I load different lengths of line on each side of the spool?
No, always load equal lengths of line on both sides. Unequal lengths unbalance the spool, leading to excessive vibration, poor trimming performance, and premature wear on the head and engine.
What happens if I run my Stihl weed eater without trimmer line?
Running a trimmer without line can damage the head’s spindle and bearings, as the metal cutting head will hit the ground or obstacles without the cushion of the line. It also causes excessive vibration and strain on the engine, leading to premature wear. Always confirm you have line loaded before operating your trimmer.
How do I know if my Stihl weed eater has an AutoCut or FixCut head?
Check the bottom of the head: AutoCut models have a small rubber bump button for line feed, while FixCut models have a small plastic adjustment knob for line length, or no button at all. You can also confirm your head type by looking up your trimmer’s model number in the user manual or on the Stihl website.
Conclusion
Learning How to Put String in Stihl Weed Eater? is a simple, high-impact skill that saves you time and money, and keeps your equipment running at peak performance for years. Whether you have an AutoCut head for residential lawn care or a FixCut head for heavy-duty commercial use, following the steps outlined in this guide will ensure you load your line correctly every time. Remember to use the right line diameter for your model, wind the line in the correct direction, and follow basic safety precautions when working on your trimmer. With these tips, you’ll be able to swap out your trimmer line in minutes, and get back to tackling your yard work without delay.