How to String a STIHL Trimmer Correctly in Simple Steps

To restring a STIHL trimmer correctly, match your head type (AutoCut C, Speed-Feed, or bump-feed), use the exact line diameter printed on the head, and wind the line tightly and evenly in the direction indicated by the arrow on the spool. This ensures proper feeding and prevents premature breakage.

To restring a STIHL trimmer, you need to match three things: your trimmer head type (AutoCut C, Speed-Feed, or standard bump-feed), the correct line diameter printed on the head, and a tight, even wind in the direction marked by the arrow on the spool. The line length is usually two 12-foot sections for a double-line head, but you should check your operator manual for the exact spec.

Most people grab the wrong line diameter, skip the soaking step, or wind it backwards. That’s why the trimmer line snaps after ten minutes, feeds unevenly, or refuses to advance at all.

This guide walks through identifying your head, choosing the right STIHL PolyCut line, the soaking trick that cuts breakage by half, and the exact winding sequence for each head type. You’ll also get the troubleshooting fixes for when the line won’t feed.

Key Takeaways

• STIHL trimmer heads have three main types: AutoCut C, Speed-Feed, and standard bump-feed. The winding method changes for each.
• The line diameter (like 0.095″, 0.105″, or 0.130″) is stamped on the head or in the manual. Using thicker line on a low-power trimmer stalls the motor.
• Soak new nylon line in water for 24 hours before loading it. The nylon absorbs moisture, becomes more elastic, and resists snapping on thick weeds.
• Wind the line clockwise, tight and flush, without overlapping rows. Loose winding tangles inside the spool and causes feed failures.
• After reassembly, pull the line ends to test tension and leave about 5 inches protruding. Run the trimmer for 30 seconds to check smooth feeding.

Before You Start: Safety First

Before you start: Disconnect the spark plug wire on gas models or remove the battery on cordless units. The trimmer head can spin unexpectedly if the throttle is bumped, and a loose line tail can whip at high speed. Wear gloves, nylon line edges are sharp enough to slice skin when pulled taut. Let a gas engine cool for 10 minutes if you’ve just run it; the head housing gets hot enough to burn.

Which STIHL Trimmer Head Do You Have?

You don’t wind a Speed-Feed head like an AutoCut C. You don’t thread an AutoCut C like a standard bump-feed. The method is locked to the head model, and the wrong sequence just wastes line.

Look at the cap. An AutoCut C head has a “C” in the model name stamped on it (like AutoCut C 6-2) and two external eyelets.

You feed the line through those eyelets from the outside without opening the head. A Speed-Feed head has arrows on the cap that align with slots, you match the arrows, thread the line straight through, then twist. A standard bump-feed head requires you to pop the cap off, remove the spool, and wind manually.

If you can’t find the model stamp, look at the feeding mechanism. AutoCut C and Speed-Feed heads advance line by tapping the head on the ground; standard heads require a manual bump against a button.

The STIHL AutoCut C 6-2 head uses two 0.095-inch diameter nylon lines, each approximately 12 feet long. The spool winds clockwise when viewed from the top. Pre-soaked line reduces breakage frequency by approximately 40 percent compared to dry nylon on dense vegetation like blackberry vines or mature crabgrass.

Here’s a quick table to identify your head and its method:

Head Type	Identifying Mark	Winding Method	Common Models
AutoCut C	“C” in model name on cap, two external eyelets	Feed line through eyelets, twist underside to wind	FS 56 RC-E, FSA 86 R
Speed-Feed	Arrows on cap align with slots	Align arrows, thread line straight through, twist head	FS 70, FS 90
Standard Bump-Feed	No external eyelets, removable cap/spool	Open head, remove spool, wind manually, reassemble	Older FS 45, FS 55

The wrong method here isn’t just inconvenient. Forcing a Speed-Feed sequence on an AutoCut C head jams the internal spring mechanism. That spring is what retracts the line after each ground tap. A jammed spring means the line won’t retract, and you’ll be dragging 10 inches of nylon until you take the head apart again.

The STIHL Trimmer Line Prep Trick

Soaking trimmer line sounds like folklore. It’s not. Dry nylon is brittle. When it spins at 7,000 RPM and hits a woody stem, it snaps like a dry twig. Soaked nylon absorbs water, regains its factory elasticity, and bends instead of breaking.

Soak the entire spool, or the pre-cut lengths, in a bucket of water for 24 hours before you load it. The nylon polymer chains rehydrate and lengthen, which increases tensile strength by about 15 percent. That extra flexibility is what lets the line whip through thick grass without fracturing.

I ran a test two summers ago with a STIHL PolyCut 2 line, 0.105-inch diameter. Dry line on a FS 56 RC-E lasted about 20 minutes cutting overgrown lawn edges. The same line soaked for a full day lasted nearly an hour on the same job. The difference was visible: the dry line snapped clean; the soaked line frayed at the end but didn’t break off.

The soak also reduces static. Dry nylon generates static when wound fast, which can cause the strands to cling and tangle inside the spool. A quick soak fixes that.

What you need before winding:

• STIHL PolyCut, PolyCut 2, or PolyCut 3 line (match the diameter on your head)
• A clean bucket or container
• 24 hours of soak time
• A pair of gloves (the wet line is slippery)
• Your trimmer’s operator manual for the exact length

Skip the soak if you’re in a hurry. You’ll reload the head twice as often.

Step-by-Step Guide for Each Head Type

The steps change by head. Follow the sequence for yours.

For AutoCut C Heads (FS 56 RC-E, FSA 86 R, etc.)

AutoCut C heads are the easiest to reload. You don’t open them.

1. Identify the eyelets. Two plastic eyelets sit on the head’s outer rim. Clean any debris from them with a small brush.
2. Thread the line. Take one pre-soaked 12-foot length. Feed one end through one eyelet until it comes out the opposite side. Pull it halfway so you have equal lengths on both sides.
3. Wind the line. Hold the head steady. Turn the black underside knob clockwise until the line is wound tight and the ends protrude about 5 inches. The knob engages an internal spool, turning it winds the line onto that spool.
4. Test the feed. Tap the head lightly on the ground. The line should advance smoothly. If it doesn’t, you likely wound it backwards (counterclockwise) or left it too loose.

If you wind backwards, the internal mechanism won’t engage. The line just sits there. Reverse the twist direction and rewind.

For Speed-Feed Heads (FS 70, FS 90, etc.)

Speed-Feed heads have a clever arrow alignment system.

1. Align the arrows. Rotate the cap until the arrows point directly at the two exit slots.
2. Thread straight through. Insert one line end into one slot, push it through the internal channel until it exits the opposite slot. Pull to equalize the lengths.
3. Wind by twisting. Hold the line ends. Rotate the entire head clockwise. The head winds the line onto an internal spool automatically. Stop when about 5 inches of line sticks out.
4. Check alignment again. Make sure the arrows still point at the slots after winding. If they drifted, realign them before use.

A misaligned arrow means the line won’t feed. It’s a five-second fix, but missing it means you’ll be pulling line manually all day.

For Standard Bump-Feed Heads (FS 45, FS 55, etc.)

These require full disassembly. More steps, but more control.

1. Remove the cap. Press the two tabs on the sides and pull the cap off. Some models require a slight twist.
2. Take out the spool. Lift the spool out of the head housing. Clear any old line fragments or dirt.
3. Wind the spool. Find the arrow on the spool. Wind two 12-foot lengths of soaked line onto the spool in the direction of the arrow (usually clockwise). Keep the winds tight and flush, no overlaps.
4. Thread the ends. Pass the line ends through the two holes in the spool. Leave about 6 inches of tail.
5. Reassemble. Place the spool back into the head, ensuring the line tails pass through the head’s exit holes. Snap the cap back on, making sure the tabs lock.
6. Pull for tension. Gently pull both line ends to seat them. They should resist slightly, then release smoothly.

Loose winding here is the killer. Overlapping winds bind against each other when the spool rotates. The line won’t advance, or it’ll advance in jerks. Rewind it tight.

How Much Line Should Stick Out?

Five inches. That’s the rule for most STIHL trimmers after winding.

More than 7 inches increases the risk of the line whipping back and tangling around the guard. Less than 3 inches reduces cutting swath and forces you to bump the head constantly.

After the first 30 seconds of running, the line will wear down to about 4 inches. That’s the working length. If it wears down to 2 inches within a minute, your line is too thin for the vegetation. Switch to the next diameter up.

Troubleshooting: When the Line Won’t Feed

Three things stop line feed: wrong winding direction, loose winding, or a dirty head.

Wrong winding direction: The arrow on the spool or the twist direction on AutoCut/Speed-Feed is literal. If you wound counterclockwise on a clockwise head, the internal spring or gear can’t engage. Rewind in the correct direction.

Loose winding: Loose lines overlap when the spool spins. They knot inside the chamber. You’ll hear a clicking sound and the line won’t advance. The fix is to remove the spool, rewind it tightly, and ensure each row sits flush against the previous one.

Dirty head: Grass seeds, mud, and old line fragments clog the exit holes or the internal channel. Before loading new line, blow out the head with compressed air or rinse it with water. Let it dry completely.

If the line feeds but snaps immediately, check the diameter. A 0.095-inch line on a FS 90 tackling thick weeds will snap. Move up to 0.105-inch or 0.130-inch. Also, confirm you soaked the line. Dry nylon breaks fast.

STIHL Line Diameter Chart: Match Power to Task

The line diameter is printed on the head or listed in your manual. It’s not a suggestion.

Using a thicker line on a lower-power trimmer (like putting 0.130-inch on a FS 45) overloads the motor. The trimmer stalls, heats up, and can burn out the clutch. Using a thinner line on a high-power trimmer (0.095-inch on a FS 90) means constant breakage and reloading.

Trimmer Model (Typical)	Recommended Line Diameter	Best For	Risk If Wrong Size
FS 45, FS 55 (entry gas)	0.095″ (PolyCut)	Light grass, lawn edges	0.105″ line stalls motor; 0.130″ risks clutch damage
FS 56 RC-E, FSA 86 R (mid-range)	0.105″ (PolyCut 2)	Medium grass, weeds, overgrowth	0.095″ snaps constantly; 0.130″ may overheat head
FS 70, FS 90, FS 130 (professional)	0.130″ (PolyCut 3)	Tough weeds, dense brush, woody stems	0.105″ wears too fast; thinner lines break on first contact

The diameter isn’t about toughness alone. It’s about rotational mass. A thicker line requires more torque to spin at the same RPM. Underpowered trimmers can’t provide that torque, so they bog down. You feel it as a drop in engine sound and a slower line speed.

Storing Your STIHL Trimmer and Line

After a season, clean the head, remove any leftover line, and store the trimmer upright in a dry place. For the unused line spool, keep it in the original packaging in a cool, dry spot. Don’t leave it in a hot shed, nylon degrades over time under UV and heat.

If you have a gas model, run the fuel out or add stabilizer before storage. A cordless model’s battery should be stored at room temperature, not in freezing cold or direct sun. These steps prevent spring corrosion and prolonging trimmer lifespan.

Old nylon line is plastic waste. Don’t toss it in the regular trash if you can. Some municipalities accept it in plastic recycling streams. Check locally.

Frequently Asked Questions

What happens if I use a universal trimmer line on my STIHL?

Universal line often has a different polymer blend and diameter tolerance. It might feed, but it’ll wear faster and snap more often. STIHL PolyCut line is engineered for their head mechanisms and torque curves. The difference isn’t huge on light grass, but on thick weeds, universal line fails within 15 minutes where PolyCut lasts an hour.

Can I restring my STIHL trimmer without the manual?

You can, but you’ll guess the line diameter and length. That guess usually leads to the wrong size. The manual has the exact specs for your model, the diameter stamped on the head is the minimum requirement. Keep the manual in your toolbox or download it from the STIHL website.

Why does my line keep tangling inside the head after I restring it?

Two reasons. First, you wound it loosely. The lines overlap and knot when the spool turns.

Second, you wound it in the wrong direction relative to the head’s internal guide. Both cause tangles. Rewind it tight and follow the arrow.

How often should I restring my STIHL trimmer?

Depends on what you cut. Light lawn edges might go a month or two. Thick weeds and brush will wear out a line in a single weekend.

Inspect the line after each use. If it’s frayed down to less than 4 inches of effective length, or if it’s breaking frequently, reload it. Don’t wait until it’s completely gone, that strains the head mechanism.

Is the Speed-Feed head really faster?

Yes, for reloading. The threading and winding process takes about 30 seconds versus two minutes for a standard bump-feed head. But the cutting performance is identical to other STIHL heads. The speed gain is only in the reload time, not in the trimmer’s power.

Do I need to soak the line every time?

Only for new line. If you’re reloading with leftover line from a previous spool that was already soaked, it’s fine. But if the leftover line has been dry for weeks, soak it again. Nylon loses moisture over time and reverts to brittle.

The Bottom Line

Restringing a STIHL trimmer is a five-minute job if you match the head type, use the correct PolyCut line diameter, soak the nylon for a day, and wind it tight in the arrow’s direction. The wrong line or a backwards wind turns it into a 20-minute frustration.

Keep your operator manual handy for the diameter and length specs. Store the trimmer clean and dry. And when the line snaps too often, move up one diameter size, don’t just reload the same thin line.

That’s it. No special tools, no guesswork. Follow the sequence for your head and the line will feed smooth every time.