How to Load a STIHL Strimmer Spool

24 hours is STIHL’s recommended soaking time for replacement trimmer line before you wind or use it; the exact length and diameter to load depend on the trimmer head fitted to your strimmer. Once you identify the head type, you can either rewind the exposed spool, load line from the outside on a comfort head, or install a compatible pre-filled spool.

How STIHL Strimmer Spools Work

A STIHL strimmer head holds cutting line on a spool and feeds it out through one or two openings as needed. The reloading method depends on the name printed on the head, not just the model name on the trimmer shaft or engine.

STIHL has separate loading instructions for heads including AutoCut®, AutoCut® C (EasySpool™), STIHL FixCut™, and STIHL TrimCut™. Check the lettering molded into or printed on the head before taking anything apart.

A head with a “C” in its name is generally a comfort-function head. These heads are designed to accept line from the outside, then wind it onto the spool when you twist the lower part of the head. Do not open a comfort head as though it were a standard removable-spool head unless its specific instruction card calls for that method.

How to Load a STIHL Strimmer Spool

A STIHL strimmer spool is loaded by matching approved line to the fitted head and winding it in the spool-arrow direction.

Step 1: Power Off and Clean the Trimmer Head

Make sure the strimmer is completely powered off before beginning maintenance.
Brush away grass, soil, and wound-up debris from the head, line outlets, and cover.
Work on a clean surface so that you do not lose a spring, spool, cover, or retaining part when the head is opened.

Cleaning first matters because packed debris can hide the spool arrows, keep the cover from seating correctly, or make it harder to see how the line routes through the head.

Step 2: Match the Line to the Fitted Head

Use only line approved for your particular STIHL trimmer head. STIHL line is not universally interchangeable: the trimmer head instruction card specifies both the required line diameter and the length to load.

If you no longer have the physical card, open the digital instruction card for the fitted head through STIHL Product Instruction Manuals.

Before winding, soak the replacement line in water for 24 hours. This helps keep the line more flexible while it is wound around the spool and used in the head.

Color can help identify STIHL line. For example, red STIHL mowing line is 2.7 millimeters in diameter.

Head Type or Marking	Correct Loading Route	Key Point
Standard STIHL head without a comfort function	Remove and open the head, then wind line onto the exposed spool	Follow the direction arrows on the spool
STIHL comfort head with “C” in the name	Feed line through the head from outside, then twist the lower section	Start with equal lengths sticking out on both sides
Compatible pre-filled spool	Open the head and replace the old spool	Use a spool made for that exact head
AutoCut, AutoCut C, FixCut, or TrimCut	Use the instruction card or STIHL’s head-specific tutorial	These heads can have different internal layouts

Step 3: Rewind a Standard STIHL Trimmer Head

A standard head requires you to remove the head from the strimmer, open it, and wind line directly onto the spool.

Remove the trimmer head from the brushcutter or strimmer as directed for the fitted model.
Open the head and lift out the spool carefully. Keep the cover, spring, and spool together in the order they came apart.
Remove old line and any trapped grass from the spool and housing.
Cut the replacement line to the exact length stated on the instruction card for that head. Secure the end in the spool’s anchor point if your spool has one.
Wind the line neatly in the direction of the arrows molded into the spool. Keep the coils snug and parallel rather than crossing them over each other.
Place the free line end or ends in the spool’s holding notches, if fitted, so they stay put while you reassemble the head.
Thread the line through the head’s outlet eyelets, seat the spool and spring correctly, and snap or fasten the cover back into place.
Reattach the head to the trimmer. Pull the line ends gently to release them from any holding slots, if your head uses them.

The arrows matter. Winding against them can prevent the line from feeding correctly when you bump or advance the head.

Load a STIHL Comfort Head From the Outside

Cut line to the length specified on the instruction card for the exact comfort head.
Feed the line straight through the openings in the trimmer head.
Pull the line until equal lengths protrude from both sides of the head.
Hold the head steady and twist the underside in the indicated winding direction. This winds the line onto the internal spool.
Continue until the specified amount of line has been taken into the head and the line is routed normally through both outlets.
Check that the head casing is fully closed and that the two line ends move freely.

Install a Pre-Filled STIHL Spool

A pre-filled spool is the fastest option when you do not want to wind loose line yourself.

Buy a pre-filled spool that is compatible with the exact STIHL head installed on your strimmer.
Remove the head from the machine if required, then open the head carefully.
Lift out the empty spool and remove dirt or old line fragments from the housing.
Set the new spool into the head in the same orientation as the old one.
Guide the line ends through the outlet eyelets and make sure the spring, if present, is seated correctly.
Refit the cover until it locks securely, then reinstall the head on the strimmer.
Pull both line ends lightly to make sure they are free to feed and not trapped beneath the cover.

Fix Common STIHL Spool Reloading Problems

Most line-feeding problems are easier to fix by reopening the head and correcting the winding than by forcing the line out.

Problem	Likely Cause	What to Do
Line will not feed	Line is wound in the wrong direction, crossed, or packed unevenly	Open the head, remove the line, and rewind in the direction of the spool arrows
Head will not close	Spool, spring, or line is not seated correctly	Remove the spool, clear debris, reseat the parts, and route line through the outlets before closing
One line end is much shorter	The line slipped while loading or was not centered in a comfort head	Reopen the head or feed the line through again so both sides start even
Line pulls back into the head	The ends were not routed through the outlet eyelets correctly	Open the cover and guide the line through the proper exit paths
Trimmer vibrates after reloading	The spool is not seated, or line is caught under the cover	Power off, open the head, remove trapped line, and reinstall the spool correctly

If the spool looks damaged, the cover will not lock, or the head has cracks, replace the damaged part before using the strimmer.

Check the Load Before You Start Trimming

A properly loaded spool should sit flat in the head and let the cutting line exit through its intended openings.

Before you trim:

Confirm that the cover is fully locked or secured.
Check that line is not pinched between the spool and cover.
Make sure both line ends are in the correct outlet eyelets on a two-line head.
With the trimmer powered off, turn the head by hand to make sure it is seated normally and not rubbing on the housing.
Start the trimmer according to its operating instructions and stop immediately if the head shakes, makes an unusual noise, or fails to feed line.

Store spare line clean and dry, and keep the instruction card with the trimmer or its replacement parts.

Frequently Asked Questions

How much line do I put on my STIHL trimmer?

There is no one line length for every STIHL trimmer. The instruction card for the fitted trimmer head gives the exact line length and diameter to load; if the card is missing, find the digital version through STIHL Product Instruction Manuals.

How do I respool a STIHL FS 40?

First identify the trimmer head fitted to your strimmer, because the power-unit model does not tell you the spool-loading method. A standard head is opened and wound following its arrows, while a comfort head marked with “C” is loaded from the outside by inserting line and twisting the lower part of the head.

What does the C mean on a STIHL trimmer head?

The “C” identifies a STIHL comfort-function head. Feed the correct length of line through the head with equal lengths protruding from each side, then wind it onto the internal spool by twisting the underside of the head.

Can I use red STIHL trimmer line?

Red STIHL mowing line is 2.7 millimeters in diameter. Use it only when the instruction card for your exact trimmer head approves that diameter, since thicker line needs more power and may not fit or feed correctly in every head.

Can I use a pre-filled spool instead of winding loose line?

Yes, provided the pre-filled spool is made for the exact STIHL head on your strimmer. Open the head, remove the old spool, seat the replacement spool correctly, route the line through the outlet eyelets, and close the cover securely.