Introduction
Restringing a Stihl FS 38 weed eater is a routine maintenance task that keeps the trimmer cutting cleanly and efficiently. Whether you are a homeowner tackling a weekend yard project or a professional landscaper who relies on the FS 38 for daily work, knowing how to restring the trimmer head correctly saves time, reduces frustration, and extends the life of the cutting line. This guide walks you through every step of the process, from gathering the right tools to testing the finished line, and includes practical tips, common pitfalls, and a handy comparison of line types so you can choose the best option for your needs.
- Understanding the Stihl FS 38 Trimmer Head
- Tools and Materials Needed
- Safety Precautions
- Removing the Old Line
- Preparing the New Trimmer Line
- Step‑by‑Step Restringing Process
- Winding Techniques: Single vs Dual Line
- Reassembling the Trimmer Head
- Testing and Adjusting Line Length
- Common Mistakes and How to Avoid Them
- Maintenance Tips for Longer Line Life
- Frequently Asked Questions
- Conclusion
Understanding the Stihl FS 38 Trimmer Head
The Stihl FS 38 uses a bump‑feed, semi‑automatic trimmer head that holds a spool of nylon line. When the head is tapped against the ground, a spring‑loaded mechanism releases a short length of line, keeping the cutting edge fresh without manual feeding. The head consists of a housing, a spool, a spring, a bump knob, and a retaining cap. Familiarity with these components makes the restringing process smoother because you will know exactly which parts to remove, inspect, and reassemble.
Most FS 38 models ship with a 0.095‑inch (2.4 mm) round line, but the head can accommodate diameters ranging from 0.080 inch to 0.105 inch depending on the cutting conditions. Thicker line lasts longer in heavy brush, while thinner line offers less resistance and a cleaner cut on grass. The spool capacity is roughly 20 feet of line, which translates to about 10 feet per side when using a dual‑line configuration.
Tools and Materials Needed
Before you begin, gather the following items so you won’t have to pause mid‑job:
- Replacement trimmer line (matching the diameter recommended for your work)
- Clean rag or shop towel
- Small flat‑head screwdriver (for prying the retaining cap if needed)
- Needle‑nose pliers (helpful for pulling the old line out of the spool)
- Work gloves (protect hands from sharp line ends)
- Safety glasses (protect eyes from debris)
Having a clean workspace and a container for the old line prevents accidental tangles and keeps the area tidy.
Safety Precautions
Safety should never be an afterthought when working with power equipment. Follow these precautions every time you service the FS 38:
- Turn off the engine and disconnect the spark plug wire to eliminate any chance of accidental start‑up.
- Allow the trimmer to cool completely if it has been running; hot components can cause burns.
- Wear safety glasses and gloves throughout the procedure.
- Work on a stable, flat surface to prevent the trimmer from tipping.
- Keep children and pets away from the work area.
These simple steps dramatically reduce the risk of injury and protect the tool from damage.
Removing the Old Line
Start by removing the trimmer head from the shaft. Most FS 38 models use a quick‑release button on the head housing; press it and pull the head straight off. Once the head is free, locate the retaining cap on the bottom of the spool. Turn the cap counter‑clockwise to unscrew it. If the cap is tight, a flat‑head screwdriver can provide extra leverage.
With the cap removed, lift the spool out of the housing. You will see the old line wound around the spool core. Use needle‑nose pliers to grasp the free end of the line and pull it off. If the line is brittle, it may break; simply continue pulling until the spool is empty. Discard the used line responsibly.
Preparing the New Trimmer Line
Uncoil the new line from its packaging and lay it flat to remove any memory curls. Measure a length of approximately 20 feet (about 6 meters) for a dual‑line setup, or 10 feet for a single‑line configuration. Cut the line cleanly with scissors or a utility knife; a clean cut prevents fraying that can jam the feed mechanism.
If you are using a dual‑line spool, fold the measured line in half to find the midpoint. This midpoint will sit in the spool’s central anchor hole. For a single‑line spool, simply thread one end through the anchor hole and leave the other end free for winding.
Step‑by‑Step Restringing Process
- Anchor the line: Insert the midpoint (dual) or single end into the spool’s anchor hole. Pull it through until the line is centered.
- Wind the line: Hold the spool firmly and wind the line in the direction indicated by the arrow on the spool (usually clockwise). Keep the wraps tight and even, avoiding overlaps that can cause feeding problems.
- Leave a tail: Stop winding when about 6 inches of line remain on each side. These tails will feed out when the bump knob is tapped.
- Secure the tails: Tuck each tail into the corresponding notch or slot on the spool flange. This prevents the line from unwinding during re‑assembly.
- Reinstall the spool: Place the spool back into the head housing, ensuring the spring sits correctly in its seat.
- Replace the retaining cap: Screw the cap back on clockwise until snug. Do not overtighten; the cap should turn freely but stay in place.
- Reattach the head: Align the head with the shaft, press the quick‑release button, and push the head until it clicks into place.
- Reconnect the spark plug wire: Restore the electrical connection and you are ready to test.
Following these steps in order ensures the line feeds smoothly and the head remains balanced during operation.
Winding Techniques: Single vs Dual Line
Choosing between a single‑line and dual‑line setup depends on the type of vegetation you typically cut. The table below compares the two approaches for the FS 38 head.
| Feature | Single Line | Dual Line |
|---|---|---|
| Cutting width | Narrower, ideal for fine grass | Wider, better for thick weeds and brush |
| Line consumption | Lower, line lasts longer per foot | Higher, two lines wear simultaneously |
| Feed reliability | Very consistent, less chance of jams | Slightly more prone to tangling if wound unevenly |
| Power demand | Less load on the engine | More load, may reduce RPM under heavy load |
| Best use case | Lawns, light trimming | Overgrown areas, mixed grass and weeds |
For most homeowners, a dual‑line configuration with 0.095‑inch line offers a good balance of cutting speed and line life. Professionals who frequently tackle dense brush may prefer a single, heavier line (0.105 inch) to reduce feed interruptions.
Reassembling the Trimmer Head
After the spool is wound and the retaining cap secured, double‑check that the spring is seated correctly and that the bump knob moves freely. Press the bump knob a few times; you should feel a slight resistance and hear a faint click as the line advances. If the knob feels stuck, remove the cap again and verify that the line tails are properly tucked into the notches.
Slide the head back onto the drive shaft, aligning the drive splines. Press the quick‑release button and push until you hear a solid click. Give the head a gentle tug to confirm it is locked. Finally, reconnect the spark plug wire and you are ready for a test run.
Testing and Adjusting Line Length
Start the engine and let it warm up for a minute. With the trimmer running at low speed, tap the bump knob against a firm surface (a piece of scrap wood works well). The line should extend a few inches each tap. Measure the exposed line; the ideal length is about 4–5 inches on each side for a dual‑line head. If the line is too long, it can slap the guard and cause vibration; if too short, cutting efficiency drops.
To adjust, stop the engine, disconnect the spark plug, and pull the line manually through the eyelets until the desired length is achieved. Some users prefer to pre‑cut the line to the exact length before winding, which eliminates the need for post‑assembly trimming.
Common Mistakes and How to Avoid Them
- Winding in the wrong direction: Always follow the arrow on the spool. Reverse winding causes the line to feed backward and jam.
- Over‑filling the spool: Excess line creates bulges that prevent the bump mechanism from releasing line smoothly. Stop winding when the spool is about 90 % full.
- Using the wrong line diameter: Too thick a line overloads the motor; too thin a line breaks prematurely. Stick to the manufacturer’s recommended range.
- Neglecting the spring: A mis‑seated spring leads to inconsistent line feed. Verify spring placement each time you open the head.
- Forgetting to disconnect the spark plug: This is a safety hazard and can cause accidental starts while your hands are near the head.
Awareness of these pitfalls saves time and prevents damage to both the trimmer head and the engine.
Maintenance Tips for Longer Line Life
Proper care extends the interval between restringing sessions and keeps the FS 38 performing at its best.
- Store the trimmer in a dry, shaded area; UV exposure degrades nylon line.
- Clean the head after each use to remove grass sap and debris that can cause the line to stick.
- Inspect the line for nicks or fraying before each job; replace damaged sections early.
- Lubricate the bump knob pivot lightly with a silicone spray once per season to maintain smooth operation.
- Rotate the spool 180 degrees halfway through the season if you notice uneven wear on one side.
These habits reduce line consumption and keep the feed mechanism reliable.
Frequently Asked Questions
How often should I restring my Stihl FS 38?
Restringing frequency depends on usage intensity. For typical residential use, expect to restring every 3–5 hours of cutting time. Heavy commercial work may require restringing after each job.
Can I use any brand of trimmer line with the FS 38?
Yes, as long as the line diameter falls within the 0.080–0.105 inch range and the line is rated for bump‑feed heads. Premium lines with reinforced cores often last longer.
Why does the line keep jamming after I restring?
Jamming is usually caused by overlapping wraps, incorrect winding direction, or a mis‑seated spring. Re‑wind carefully, following the arrow, and ensure the spring sits flat in its recess.
Is it necessary to remove the head from the shaft to restring?
Removing the head provides better access and reduces the risk of damaging the shaft or drive splines. While it is possible to restring with the head attached, the process is more cumbersome and error‑prone.
What is the best line diameter for general yard work?
A 0.095‑inch round line offers a good compromise between durability and cutting efficiency for most lawns and light brush.
Conclusion
Restringing a Stihl FS 38 weed eater is a straightforward task when you understand the head components, follow the correct winding direction, and observe basic safety steps. By preparing the right tools, choosing the appropriate line diameter, and winding the spool evenly, you ensure reliable line feed and optimal cutting performance. Regular maintenance—cleaning the head, inspecting the line, and lubricating the bump knob—further extends the life of both the line and the trimmer. With the step‑by‑step process outlined above, you can confidently tackle the job yourself, saving money on service calls and keeping your FS 38 ready for any trimming challenge.