Stihl Trimmer Restringing (Step-by-Step)
To restring a STIHL trimmer, first identify the exact cutting head and confirm its approved line size, loading method, and winding direction in the operator’s manual. Disable the machine, inspect the head, wind the line neatly as marked, and refit it. Test line feed with the deflector fitted. Head designs differ, so do not guess.
A trimmer can run well all season, then run out of line halfway through edging a path. The fix seems simple, until the spool will not close or the line refuses to feed. The key is matching the restringing method to the head on your machine. STIHL uses several head designs, and their loading steps are not all the same.
I check the head before touching the spool. A model name on the trimmer helps, but the head itself matters too. Once you know which head you have, the manual can tell you the line size, how much to load, and which way to wind it. That small check prevents most avoidable reload problems.
Identify the head and line before restringing
A cutting head is the assembly that holds and feeds the trimmer line. Its shape and loading features determine how you open it, where the line enters, and how it winds. Find the head name or part marking, then check the matching operator’s manual before choosing line or opening the spool.
Look for a label or marking on the head, and note the trimmer model as well. If the head has been replaced, the trimmer model alone may not identify the correct loading steps. Use the manual for the head fitted to the machine, not a similar-looking head found online.
Common STIHL AutoCut-compatible round line sizes include 2.0 mm (0.080 in) and 2.4 mm (0.095 in). These are examples, not a universal fit. Your manual sets the permitted diameter and line type. An oversized line can bind in the spool or eyelets, while a line that is too small may not feed as intended.
| What you find | What to confirm in the manual | Why it matters |
|---|---|---|
| Head with a removable spool | Line diameter, winding direction, and loading length | Prevents crossed or overfilled wraps |
| Head with line-loading openings | How to align, feed, and wind the line | Avoids forcing line into the wrong path |
| Unclear head marking | Head part number or approved replacement | Similar heads may use different methods |
| Damaged or worn head | Approved replacement parts | Cracks or worn retainers can prevent safe use |
Do not assume that every STIHL head uses the same line length or winding direction. Both spool capacity and winding instructions vary. Takeaway: identify the head first, then prepare only the line and amount specified for it.
Prepare the trimmer safely
Safe restringing means the cutting head cannot start while your hands are near it. Stop the engine or switch off the battery unit, wait for the head to stop, and let hot parts cool. Wear gloves and eye protection while handling line, and do not open a head that is still powered.
For a gas trimmer, disconnect the spark-plug boot before servicing the head. For a battery trimmer, remove the battery. Keep the machine disabled until the spool and cover are back in place. Before you begin, check that the deflector is fitted securely and is not cracked or badly worn.
Inspect the head’s cover, spool, eyelets, and retaining parts. Eyelets are the openings that guide line out of the head. Stop and replace damaged parts using the model-specific instructions; do not try to make a cracked cover work. Never run the trimmer with a missing or damaged deflector or line-limiting blade.
Lay out the correct line, scissors or a line cutter, and the manual. Cut only the length the manual specifies. If the manual gives no single length because the head uses a different loading method, follow that method instead of estimating. Takeaway: do not reconnect power or the spark-plug boot until the head is reassembled and secure.
Restring the head step by step
Restringing means placing fresh line in the spool and routing it through the head’s outlets. Some heads let you load line without removing the spool; others require you to open the head and wind the spool by hand. Follow the steps for your exact head, and stop if the parts do not match the manual.
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Open or access the head as directed. With the machine disabled, release the cover or expose the loading openings using the manual’s method. Avoid prying at retaining tabs or forcing the cover. If it will not release as shown, check the head instructions before applying more pressure.
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Remove and inspect the spool if required. Note how the spool sits before lifting it out. Check for grass, old line, melted line, cracks, or damaged retaining features. Clear debris without damaging the spool or eyelets. Replace a damaged part rather than trying to wind around it.
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Cut and prepare the line. Use the specified diameter and type. Cut the required length or lengths for that head. If the head takes two line pieces, keep them separate. Do not substitute oversized line or push line through a hole that does not match the manual’s loading path.
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Feed and wind the line. Put the line into the correct opening, then wind it in the direction marked on the spool or stated in the manual. Keep each wrap next to the last one, without crossing, bunching, or pulling it tight enough to distort the spool. Orderly wraps help the line leave the spool cleanly.
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Secure the ends. If the spool has holding notches, place the line ends in them as shown. These notches keep the line from unwinding while you refit the spool. Do not cut the line shorter unless the instructions call for it.
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Refit the spool and route the ends. Place the spool in its correct position and pass each line end through the matching eyelet. Make sure the line is not trapped under the spool or cover. Refit the cover and lock it using the method shown in the manual. It should seat without force.
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Check movement before restoring power. Pull each exposed end to confirm that it moves as the head design allows. If it jams, stop and reopen the head. Look for crossed wraps, the wrong line size, an incorrectly seated spool, or a blocked eyelet. Do not force the cover closed.
| Head loading style | Typical action | Check before continuing |
|---|---|---|
| Spool removed for winding | Wind line onto the spool by hand | Follow the marked direction and keep wraps orderly |
| Line loaded through head openings | Align the loading points, feed line, then wind as instructed | Confirm both ends follow the correct path |
| Head or method uncertain | Stop and consult the model-specific manual | Do not guess at line length or winding direction |
Takeaway: clean routing and correct winding matter as much as the line itself. A spool that looks full is not necessarily loaded correctly.
Diagnose common restringing problems
A head that will not feed often has a loading issue, not a reason to force the line. First disable the trimmer again. Open the head as instructed and check the wraps, line size, eyelets, spool, and cover. A small tangle can stop line from moving even when the head appears properly assembled.
| Symptom | Likely check | Next step |
|---|---|---|
| Line will not advance | Crossed wraps, fused line, or wrong diameter | Unwind and reload with approved line |
| Line breaks or sticks at an outlet | Damaged eyelet or line routed incorrectly | Inspect the eyelet and reload as directed |
| Cover will not lock | Spool not seated, too much line, or wrong part | Recheck loading and confirm the correct head parts |
| One end is much shorter | Uneven loading or a snagged end | Disable the machine, open the head, and correct the routing |
In field work, two common scenarios are easy to mistake for one another. If fresh line is loaded but will not feed, crossed wraps or an oversized diameter are worth checking first. If line feeds poorly only after the head gets dirty, inspect the eyelets and remove packed grass. These are troubleshooting examples, not proof of a single cause; inspect the actual head.
Do not bypass the line-limiting blade or remove the deflector to solve a feed problem. The blade trims line to the designed operating length. A missing or defeated blade can leave excessive line exposed, increasing the risk of line breakage and thrown debris. Takeaway: if a correct reload does not fix repeated binding, inspect for worn or damaged head parts.
Reassemble, test, and store the trimmer
A successful reload ends with a secure head, free-moving line, and a working deflector. Reconnect the spark-plug boot or reinstall the battery only after the head is fully assembled. For the test, move outdoors and clear people, pets, and loose objects from the work area.
Keep bystanders at least 15 m (50 ft) away. Start the trimmer using its manual’s cold- or warm-start procedure, with the cutting head clear of people and objects. Test line feed at operating speed as the manual directs. Do not touch the head while it is running; stop and disable the machine before inspecting it.
When trimming, avoid striking fences, rocks, and other hard objects. Contact can break line or damage the head. After use, stop and cool the machine, then remove the battery or disconnect the spark-plug boot before cleaning the head and deflector. Store the trimmer where the head is protected from impact and heat.
For a gas model, fuel-mix rules are separate from restringing. STIHL specifies a 50:1 mix when using STIHL two-stroke oil, but check the particular model’s manual for fuel and storage instructions. Takeaway: test the reload safely, then keep the head clean so debris does not interfere with the next line feed.
Frequently asked questions
These short answers cover the most common questions that come up while reloading a STIHL trimmer head. The right answer still depends on the head fitted to your machine, so use its manual for exact line size, length, and winding steps. If a part looks different, stop and verify before proceeding.
What size line does a STIHL trimmer use?
It depends on the cutting head. Common compatible round sizes include 2.0 mm (0.080 in) and 2.4 mm (0.095 in), but check your head’s manual before buying or loading line.
Which way do I wind STIHL trimmer line?
Wind in the direction shown on the spool or stated in the manual. Do not assume all STIHL heads wind the same way.
How much line should I put on the spool?
Use the loading length or capacity specified for your exact head. Too much line can bind or prevent the cover from closing correctly.
Why will my trimmer line not feed after restringing?
Check for crossed wraps, fused line, an incorrect diameter, blocked eyelets, or a spool that is not seated properly. Disable the machine before opening the head.
Can I use any brand of trimmer line?
Use line of the type and diameter approved for your head. A different brand may be suitable if it meets those requirements, but do not force incompatible or oversized line into the spool.
Do I need to remove the spool to reload the line?
Some heads require spool removal; others allow line to be fed through the head. Follow the instructions for your exact model and head design.
Can I run the trimmer without its deflector?
No. Keep the specified deflector and line-limiting blade fitted and in good condition. Do not remove, bend, or bypass them.
What if the spool cover will not close?
Do not force it. Check whether the spool is seated correctly, the line is routed as directed, or too much line has been loaded. Verify that the cover and spool match the head.
When should I replace the cutting head?
Replace damaged or badly worn parts according to the manual. If the head repeatedly binds or cannot retain line after correct loading, use the model-specific service procedure or replace the faulty components.
Does restringing require carburetor tuning?
No. Restringing is a cutting-head task. It does not use chain-sharpening, chain-tension, or carburetor-tuning steps.
(This article was written by one of our staff writers, Harrison Croft. Visit our Meet the Team page.)
