Introduction
Restringing a Stihl weed eater is a routine maintenance task that keeps your trimmer cutting cleanly and efficiently. Whether you own a compact FS 40 C‑E or a professional‑grade FS 250, the basic principles remain the same: select the correct line diameter, match the line to the head type, and load it without twists or kinks. This guide walks you through every step, from identifying your head style to pro tips that extend line life and prevent common headaches. By the end you will feel confident answering the question How to String My Stihl Weed Eater? and keeping your equipment ready for any yard job.
Table of Contents
- Understanding Your Stihl Weed Eater Head Types
- Choosing the Right Trimmer Line
- Tools and Safety Gear You’ll Need
- Step‑by‑Step: How to String My Stihl Weed Eater?
- Loading a Fixed‑Line Head
- Loading a Bump‑Feed Head
- Loading an Auto‑Feed Head
- Comparison Table: Head Types, Line Diameter, and Best Use Cases
- Pro Tips for Longer Line Life
- Common Mistakes and How to Avoid Them
- Maintenance After Restringing
- Frequently Asked Questions
- Conclusion
Understanding Your Stihl Weed Eater Head Types
Stihl trimmers ship with three primary head designs, each requiring a slightly different loading method. Knowing which head you have is the first step to a smooth restring.
Fixed‑Line Head
A fixed‑line head holds a single, pre‑cut length of line that is wound onto a spool and secured with a retaining knob. The line does not advance automatically; you replace the entire spool when the line wears down. This design is common on entry‑level models such as the FS 38 and FS 40 C‑E.
Bump‑Feed Head
The bump‑feed (or “tap‑and‑go”) head releases fresh line each time you tap the head on the ground while the engine is running. Inside, a spring‑loaded spool feeds line through an eyelet. This head appears on mid‑range units like the FS 56 RC‑E and FS 70 R.
Auto‑Feed Head
Auto‑feed heads use centrifugal force to advance line without any operator input. As the head spins, weighted arms fling line outward through the eyelet. These heads are found on high‑end professional models such as the FS 250 and FS 300. They often accept larger‑diameter line for heavy brush clearing.
Choosing the Right Trimmer Line
Line diameter, shape, and material all affect cutting performance and line longevity. Stihl recommends matching the line to both the head type and the vegetation you tackle.
Line Diameter
Common diameters range from 0.065 in (1.65 mm) for light grass to 0.105 in (2.67 mm) for thick weeds and light brush. Using a line that is too thick for a fixed‑line head can jam the spool; too thin a line in an auto‑feed head may not feed reliably.
Line Shape
Round line is the most versatile and feeds smoothly in all head types. Square, star, or twisted profiles cut more aggressively but can increase vibration and wear on the head’s eyelet. For most homeowners, a high‑quality round line in the correct diameter is the best balance of durability and ease of loading.
Line Material
Standard nylon works well for general trimming. Reinforced copolymer or “commercial‑grade” lines resist abrasion better and last longer in rocky or sandy conditions. Stihl’s own “PolyCut” and “SuperCut” lines are engineered for their heads and often provide the smoothest feed.
Tools and Safety Gear You’ll Need
Before you begin, gather the following items to make the job safe and efficient: (See Also:How To Remove Kobalt Weed Eater Head)
- Replacement trimmer line (correct diameter and length)
- Protective gloves – leather or cut‑resistant
- Safety glasses or a face shield
- Flat‑head screwdriver or the Stihl “head‑tool” supplied with the trimmer
- Clean rag for wiping debris from the head
- Workbench or stable surface at waist height
Always disconnect the spark plug lead (or remove the battery on cordless models) before opening the head. This prevents accidental starts while your fingers are near the rotating spool.
Step‑by‑Step: How to String My Stihl Weed Eater?
The following universal steps apply to every Stihl head. After the overview, you’ll find head‑specific details.
- Power down and secure the trimmer. Remove the spark plug wire or battery. Lay the unit on a clean work surface with the head facing up.
- Remove the head cover. Use the supplied tool or a flat‑head screwdriver to loosen the retaining knob or bolts. Keep all small parts in a tray so nothing gets lost.
- Take out the old spool and line. Discard any frayed or melted line. Inspect the spool for cracks; replace it if damaged.
- Cut the new line to the proper length. Most fixed‑line heads need a single piece 10–12 ft long. Bump‑feed and auto‑feed heads usually require two equal lengths (often 8–10 ft each) that will be wound onto the spool in opposite directions.
- Insert the line into the spool anchor points. Follow the arrows molded on the spool. For dual‑line heads, feed one piece into each anchor, keeping the line flat and untwisted.
- Wind the line neatly. Turn the spool in the direction indicated by the arrow (usually clockwise). Keep tension even; avoid overlapping or crossing the line.
- Leave the correct tail length. Most heads need 4–6 in of line protruding from the eyelet after winding. Trim excess with scissors.
- Reinstall the spool into the head housing. Align any notches or tabs. Snap the cover back on and tighten the retaining knob securely.
- Reconnect the spark plug or battery. Start the engine and let it idle. For bump‑feed heads, tap the head lightly on grass to advance line. For auto‑feed heads, run at full throttle for a few seconds to let centrifugal force feed the line.
- Test cut. Trim a small patch of grass. If the line feeds smoothly and cuts cleanly, you’re done.
Loading a Fixed‑Line Head
Fixed‑line heads are the simplest to service. After removing the cover, you will see a single spool with a central anchor hole. Cut a single piece of line to the length specified in your owner’s manual (typically 10–12 ft). Insert one end into the anchor hole, then wind the line tightly in the direction of the arrow. Keep the line flat against the spool flange to prevent snags. When you reach the end, leave a 5‑inch tail, thread it through the eyelet, and snap the cover back on. Because the line does not auto‑advance, you will replace the entire spool once the line wears down to the eyelet.
Loading a Bump‑Feed Head
Bump‑feed heads contain a spring‑loaded spool that holds two line sections. After opening the head, remove the spool and note the two anchor slots marked “A” and “B.” Cut two equal lengths of line (usually 8–10 ft each). Insert one end of the first piece into slot A, wind clockwise following the arrow, and leave a 4‑inch tail. Repeat with the second piece into slot B, winding counter‑clockwise if the spool indicates opposite directions. Ensure the two tails exit through the same eyelet on opposite sides. Reassemble the head, making sure the spring seats correctly. When you tap the head on the ground, the spring releases a few inches of line from each side.
Loading an Auto‑Feed Head
Auto‑feed heads rely on centrifugal force, so the line must be wound with a slight pre‑tension. Open the head and remove the spool. You will see a single anchor point and a set of weighted arms. Cut a single length of line (often 12–15 ft for professional models). Thread the line through the anchor, then wind it onto the spool in the direction of the arrow, keeping the line snug but not stretched. The weighted arms should sit flush against the spool when fully wound. Leave a 6‑inch tail through the eyelet. Reinstall the spool, ensuring the arms move freely. At full throttle the arms fling outward, pulling line through the eyelet automatically.
Comparison Table: Head Types, Line Diameter, and Best Use Cases
| Head Type | Typical Line Diameter | Line Feed Method | Ideal Application | Pros | Cons |
|---|---|---|---|---|---|
| Fixed‑Line | 0.065–0.080 in | Manual spool replacement | Light residential grass trimming | Simple, low cost, no moving parts | Frequent spool changes, limited line length |
| Bump‑Feed | 0.080–0.095 in | Tap‑to‑advance | Medium‑duty lawns, mixed grass/weeds | Quick line advance, adjustable length | Spring wear, requires user action |
| Auto‑Feed | 0.095–0.105 in | Centrifugal force | Heavy brush, commercial use | Hands‑free, handles thick line | Higher cost, more complex mechanism |
Pro Tips for Longer Line Life
- Store line in a cool, dry place. UV exposure and humidity make nylon brittle.
- Use the manufacturer’s recommended line. Stihl‑branded line is engineered for the exact eyelet geometry of each head.
- Keep the cutting height modest. Cutting too low forces the line into soil and rocks, accelerating wear.
- Clean the head after each use. Grass sap and dirt build up inside the eyelet, causing friction and uneven feed.
- Rotate the spool periodically. On bump‑feed heads, flip the spool end‑for‑end every few loads to even out wear on the anchor slots.
- Avoid over‑revving. Running the engine at max RPM when not cutting generates heat that can melt the line.
Common Mistakes and How to Avoid Them
Even experienced users slip up. Here are the most frequent errors and the fix for each.
Using the Wrong Line Diameter
Installing 0.105 in line in a fixed‑line head jams the spool and can crack the housing. Always verify the maximum diameter stamped on the head or listed in the manual.
Winding Twisted or Crossed Line
Twists cause the line to bind during feed, leading to uneven cuts and sudden line breakage. Keep the line flat and follow the spool arrows precisely.
Leaving Too Short a Tail
If the tail is shorter than the eyelet depth, the line won’t engage the feed mechanism. Measure 4–6 in beyond the eyelet before trimming.
Reassembling a Dirty Head
Debris trapped between the spool and housing creates friction, preventing smooth feed. Wipe the interior with a rag before reinstalling the spool. (See Also:How To String A Shindaiwa Weed Eater)
Forgetting the Spring on Bump‑Feed Heads
The spring must sit squarely in its recess. An omitted or mis‑seated spring means the head won’t advance line when tapped.
Maintenance After Restringing
After you have successfully restrung the trimmer, a few quick checks keep it running at peak performance.
- Run the engine at idle for 30 seconds; listen for unusual rattling that could indicate a loose cover.
- Inspect the line feed after the first few minutes of cutting. If the line is not advancing, stop and re‑check the winding direction.
- Lubricate the head’s pivot points with a light machine oil every 20 hours of operation to reduce wear on the bump‑feed spring or auto‑feed arms.
- Sharpen or replace the cutting blade (if your model has a metal blade attachment) according to the service schedule.
- Store the trimmer with the head covered or in a dry cabinet to prevent moisture from degrading the line.
Frequently Asked Questions
How often should I restring my Stihl weed eater?
Restring whenever the line wears down to the eyelet or when cutting performance drops noticeably. For typical residential use, this is every 2–4 hours of run time; heavy commercial work may require daily restringing.
Can I use any brand of trimmer line in my Stihl head?
You can, but Stihl‑engineered line matches the exact diameter tolerance and eyelet shape, reducing feed problems. Off‑brand line of the same spec usually works, but quality varies.
Why does my line keep breaking near the eyelet?
Common causes are using line that is too thick for the head, winding the line too loosely (causing it to slap the eyelet), or cutting abrasive material like rocks and concrete. Check diameter, rewind tightly, and avoid hard surfaces.
My bump‑feed head won’t advance line when I tap it. What’s wrong?
First, ensure the spring is seated and not broken. Next, verify that both line tails are the correct length and exit the eyelet cleanly. Finally, make sure you are tapping on firm ground while the engine is at operating speed. (See Also:How To String A 2 String Weed Eater)
The auto‑feed head isn’t feeding line at full throttle.
Check that the weighted arms move freely and are not bent. Confirm the line is wound in the correct direction and that the tail length meets the manual’s specification. A clogged eyelet can also block feed; clean it with compressed air.
Do I need to replace the whole spool on a fixed‑line head?
Yes. Fixed‑line heads are designed for a single‑use spool. When the line is exhausted, you remove the old spool and install a new pre‑wound spool or wind a fresh line onto the existing spool if it is reusable.
Conclusion
Restringing a Stihl weed eater is a straightforward process once you identify the head type, select the proper line, and follow the step‑by‑step loading procedure. By matching line diameter to the head, winding cleanly without twists, and performing a quick post‑load test, you ensure reliable feed and clean cuts every time. Incorporating the pro tips—proper storage, regular cleaning, and avoiding over‑revving—extends line life and reduces downtime. Avoiding the common mistakes outlined above saves frustration and protects your investment. With this comprehensive guide, you now have the knowledge to answer How to String My Stihl Weed Eater? confidently and keep your trimmer ready for any landscaping challenge.