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How to fit strimmer line on a 2.4 mm head

Updated: October 2026

The head has stopped feeding, and the last attempt left a bird’s nest in the spool. How to fit strimmer line, on a bump-feed head the manual already allows at about 2.4 mm, is a short job if you follow the arrow, keep the two ends equal, and leave the guard knife where the maker put it. Forcing more line in will not fix a wind that is already too full. This page is the procedure. It does not rank packs. Which reel to buy stays on the [2.4 mm strimmer line comparison](/hub/lawn-and-garden-equipment/2-4mm-strimmer-line) and the [2.4 mm strimmer line buying guide](/hub/lawn-and-garden-equipment/2-4mm-strimmer-line/sub/2-4mm-strimmer-line-buying-guide). Peter F. used Stihl UK, EGO UK, and public fitting notes. A qualifying purchase can earn a commission at no extra cost to you.

The head has stopped feeding, and the last attempt left a bird’s nest in the spool.

Our top picks

Viabrico Viabrico square 100 m

Best overall

Viabrico Viabrico square 100 m
9.2/10about £10.99
View offer
Zeqeey Zeqeey square 100 m

Alternative

Zeqeey Zeqeey square 100 m
7.9/10about £14.99
View offer
Oregon Oregon round 15 m

Best value

Oregon Oregon round 15 m
6.4/10about £5.99
View offer
On this page
  1. 1.Wind with the arrow, and stop at the fill line
  2. 2.Make the two ends the same length
  3. 3.Leave the guard knife where it is
  4. 4.Soak dry nylon before you argue with it
  5. 5.A refill that will feed

Wind with the arrow, and stop at the fill line

Take the battery out, or unplug the machine, before the spool cover comes off. Follow the arrow on the spool. Toolbuyer Hub’s fitting note says to lay the line in tight, flat layers and to stop at a fill line if the spool has one. Their typical figure is about 3–5 m per chamber, not a whole 100 m reel. If your manual prints a different length, the manual wins. Overfilling is why a fresh wind will not bump. The line binds and the eyelet sees a knot. A crossed wind does the same thing. One Viabrico reviewer found the supplied reel ready to unwind: hold the coil while you transfer it. Stop below the rim.

Make the two ends the same length

Most domestic heads want two tails, one from each side. If one is a hand’s width longer, the head is out of balance every revolution. HSE’s guide INDG480 quotes about 2 to 7 m/s² for the machine, not a lab figure for the cord. Match the tails before the cover goes back. Stihl’s note on Comfort-style heads says the same. An AutoCut head is a tap on the ground, not an outside wind. A tail far past the guard flaps and snaps. You want ends long enough to reach the cutter.
Viabrico Viabrico square 100 m

Testsieger

Viabrico Viabrico square 100 m
9.2/10about £10.99
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Leave the guard knife where it is

The knife on the guard stops the line growing too long on the first run. EGO UK says to tap, not hold the head down, and not to remove the cutter. Holding it down can stall a small motor and throw offcuts. Wear eye protection. HSE treats strimmer work as a projectile risk. Bump once on grass. The tails should lengthen, then meet the guard. A head that dumps the whole wind was wound the wrong way. A head that clicks and feeds nothing is usually overfilled or blocked at a worn eyelet. A welded lump is heat and a bad wind, not a thicker diameter.

Soak dry nylon before you argue with it

Dry nylon snaps while you are still threading it. Stihl’s UK square page says to soak the reel for 12 to 24 hours. The replace-line page says at least 24 hours. Oregon’s older advice is 24 hours. Those are maker tips, not a measured gain in life. Soak before you wind if the reel has been in the sun. Do not soak a head that is already jammed. Square and star fight the spool more than round. If the eyelet will not pass the shape, soaking will not turn a 3.4 mm diagonal into round 2.4 mm. Stop if the machine vibrates, smokes, or stalls once the cord and the tails are right.

A refill that will feed

Power off, wind with the arrow, stop below the rim, and match the two tails before the cover goes on. Soak nylon that has dried in a shed, then let the guard knife trim the first spin. If the eyelet refuses a square corner, a neater wind will not change the shape. If the machine still stalls on the correct diameter with equal tails, that is a fault for someone who already works on that head.

Common questions

Which way do you wind the spool?
Follow the arrow on the spool you are holding. A wind against that arrow is a common reason the line will not feed, or dumps itself on the first start. Stihl AutoCut heads are a tap-to-feed design, not an outside wind. Comfort-style heads wind from the outside and need equal ends before you close them. Your manual beats a general diagram.
How much line goes in before the head locks?
Stop at the fill line if the spool has one, with the line below the rim and still able to move. Toolbuyer Hub’s about 3–5 m per chamber is a typical picture, not the capacity of every head. Stuffing in the rest of a 100 m reel is how bump feed locks. The leftover stays on the doughnut. Another twenty turns will not store a 253 m roll in a domestic spool.
Why do the two ends need to match?
Uneven tails unbalance the head and add vibration you can feel in the handles. HSE quotes about 2 to 7 m/s² for the machine, not a separate figure for the cord. Match the ends before the cover goes on, and let the guard knife tidy them on the first run. One tail twice as long is the shake you did not have yesterday.
How long should you soak the nylon?
Stihl UK says 12 to 24 hours on the square line page and at least 24 hours on the replace-line page. Oregon’s older advice is 24 hours. Soak the reel if it has dried in storage, then wind it. That is maker and reviewer advice. It is not a measured extra life, and it will not make an oversized line fit a small eyelet.
Is square line harder to wind than round?
Yes, in the guides and in the reviews. A square’s corner is wider than the stated side. Zeqeey’s file includes stiff winding and a Husqvarna spool that would not feed. Star line has five edges to lie flat. If the eyelet only just takes round 2.4 mm, soaking and a neater wind will not pass a shape that does not fit.

Related pages

Square or round 2.4 mm strimmer line

2.4 mm strimmer line for thick weeds

2.4 mm strimmer line

Best 2.4 mm strimmer line for the job in front of you

2.4 mm strimmer line: what to check before you buy

Sources

Shelf prices, star ratings and review counts are the amazon.co.uk figures captured on 19 October 2026. The other pages are public UK guidance on line profile, soak advice, vibration and garden safety.

  1. Stihl UK square 2.4 mm mowing line (retrieved 19 October 2026)
  2. Oregon UK Nylium Star 2.4 mm 90 m (retrieved 19 October 2026)
  3. Oregon profile map (retrieved 19 October 2026)
  4. ManoMano UK trimmer line buying guide (retrieved 19 October 2026)
  5. HSE chain flails and brush cutters (retrieved 19 October 2026)
  6. HSE INDG480 hand-arm vibration (retrieved 19 October 2026)
  7. RHS hedgehog-friendly gardening (retrieved 19 October 2026)
  8. GOV.UK noise nuisances (retrieved 19 October 2026)