Husqvarna Chainsaw Torque Specs

These figures come from Husqvarna's dealer workshop manuals for the 435/440e and 445/450e saws. That matters more than usual here, because Husqvarna states most of these torques twice — once as a number on the exploded-view "Service data" page and again in the repair procedure as… Read the rest ›

plain prose that names the component ("tighten to a torque of 25-30 Nm") — so each value could be cross-checked against an unambiguous text statement rather than a diagram leader line. Husqvarna specifies in newton-metres only; the ft-lb and in-lb figures here are conversions, with the N·m recorded on every row.

Where these numbers come from. 23 published figures, 4 confirmed gaps, every source named. How we checked ›

Read from the Husqvarna workshop manuals WM_435-435e-440e (5046438-26) and WM_445-445e-450e (1150342-26). Every value is identical between the two documents — Husqvarna uses one spec sheet across this range — but each engine below cites its own manual rather than one being copied onto the other. The manuals were reached on a Husqvarna parts dealer's download area, not husqvarna.com; the content is a genuine dealer workshop manual and each row's sourceType says both halves of that. This page previously carried hand-written figures with no source, including a spark-plug value of 18-22 ft-lb — roughly 50% above the 20 N·m (15 ft-lb) Husqvarna actually specifies — and a 20-25 ft-lb guide-bar-nut figure for a fastener these manuals do not publish at all. Both have been removed. The 128/129 trimmer series is recorded as a gap for a specific reason explained on its row.

Husqvarna 435 / 435e / 440e41cc Manufacturer-published

series 435, 435e, 440e

From Husqvarna workshop manual WM_435-435e-440e (5046438-26). Values cross-checked between the exploded-view service-data page and the repair-procedure prose in the same manual.

Fastener	Torque	Where it comes from
flywheel nut	18–22 ft-lbHigh	25-30 N·m. Manual prose: "Fit the nut on the shaft and tighten to a torque of 25-30 Nm." Use a flywheel holding tool — a 2-stroke has no… Why › compression stroke to brake the crank against. A trap for anyone extending this data: the same manual's exploded-view "Service data" page carries an unlabelled "23Nm" annotation near the flywheel/fan assembly, with no text naming the fastener. The 25-30 N·m figure here is the one stated in prose in the repair procedure (section 7.8) and is the one to use — do not re-source this row from the diagram.
spark plug	15 ft-lbHigh	20 N·m, stated in the repair-procedure prose as a step distinct from the clutch. Why › This is the value that matters most on this page: the figure of 18-22 ft-lb that circulates for these saws is 24-30 N·m, up to 50% above what Husqvarna specifies, into a soft alloy cylinder.
centrifugal clutch	15 ft-lbHigh	20 N·m, specified as a MINIMUM ("tightening torque min. Why › 20 Nm") rather than a target band — the one row on this page where going above the figure is what Husqvarna intends.
cylinder bolt4mm hex socket	10–11 ft-lbHigh	13-15 N·m. Tighten in diagonal pairs. On a 2-stroke the cylinder and head are one casting, so this is not a head-bolt sequence.
muffler bolt, initial	71–89 in-lbHigh	8-10 N·m. This is a two-stage spec — see the retighten row below; stopping at this figure is not the finished job.
muffler bolt, retighten after run-in	106–124 in-lbHigh	12-14 N·m, applied after running the saw for about a minute so the joint has heat-cycled once.
ignition module screw	40–53 in-lbHigh	4.5-6 N·m.
starter assembly to crankcase bolt	22–31 in-lbHigh	2.5-3.5 N·m.
starter pulley centre bolt	18–27 in-lbHigh	2-3 N·m.
chain brake elbow-joint bolt and cover screw	9–13 in-lbHigh	1-1.5 N·m. A screwdriver-feel fastener — no ft-lb wrench reads this.
chain guide plate / oil pump screw	9–13 in-lbHigh	1-1.5 N·m.

1 spec not published — guide bar nut What we found ›

guide bar nutGAP: this workshop manual publishes no guide-bar-nut torque. The 20-25 ft-lb figure that circulates for these saws (and that this page used to carry) is 27-34 N·m and has no Husqvarna document behind it — for comparison, Echo specifies 20-23 N·m for the guide bar nuts on a comparable saw, so the circulating figure is high even against the nearest published equivalent. Tension the chain first, then tighten the two nuts evenly in an alternating pattern, then re-check tension.

Husqvarna 445 / 445e / 450e45cc Manufacturer-published

series 445, 445e, 450, 450e

From Husqvarna workshop manual WM_445-445e-450e (1150342-26) — this model range's own document, not the 435/440e one. More about this engine ›

Every figure is identical to the 435/440e manual; Husqvarna uses one spec sheet across the range. The decompression valve is the one fastener that appears here and not there.

Fastener	Torque	Where it comes from
flywheel nut	18–22 ft-lbHigh	25-30 N·m. Manual prose: "Fit the nut on the shaft and tighten to a torque of 25-30 Nm." Use a flywheel holding tool. Why › A trap for anyone extending this data: the same manual's exploded-view "Service data" page carries an unlabelled "23Nm" annotation near the flywheel/fan assembly, with no text naming the fastener. The 25-30 N·m figure here is the one stated in prose in the repair procedure (section 7.8) and is the one to use — do not re-source this row from the diagram.
spark plug	15 ft-lbHigh	20 N·m, from the repair-procedure prose. Not 18-22 ft-lb — that widely-circulated figure is up to 50% over Husqvarna's spec.
centrifugal clutch	15 ft-lbHigh	20 N·m, specified as a minimum rather than a band.
cylinder bolt4mm hex socket	10–11 ft-lbHigh	13-15 N·m. Tighten in diagonal pairs.
decompression valve	9–10 ft-lbHigh	12-14 N·m, specified in the cylinder-replacement procedure. Present on the 445/450 and not called out as a separate step in the 435/440e manual.
muffler bolt, initial	71–89 in-lbHigh	8-10 N·m. Two-stage spec — see the retighten row.
muffler bolt, retighten after run-in	106–124 in-lbHigh	12-14 N·m, after about a minute of running.
ignition module screw	40–53 in-lbHigh	4.5-6 N·m.
starter assembly to crankcase bolt	22–31 in-lbHigh	2.5-3.5 N·m.
starter pulley centre bolt	18–27 in-lbHigh	2-3 N·m.
chain brake elbow-joint bolt and cover screw	9–13 in-lbHigh	1-1.5 N·m.
chain guide plate / oil pump screw	9–13 in-lbHigh	1-1.5 N·m.

1 spec not published — guide bar nut What we found ›

guide bar nutGAP: not published in this workshop manual either. See the note on the 435/440e row — the circulating 20-30 ft-lb figures for Husqvarna bar nuts have no manufacturer document behind them.

Husqvarna 128 / 129 trimmer series28cc

series 128C, 128L, 128R, 129C, 129L, 129R, 129DJX

A genuine Husqvarna dealer workshop manual for this series exists and contains a "Service data" page with roughly 17 torque figures on it… More about this engine ›

but presented ONLY as bare numbers pinned to an exploded-view diagram by leader lines, with no text label naming any component anywhere in the document. Reading those values means tracing a leader line by eye, and a mis-traced line on a flywheel nut is exactly the error that hurts somebody. So this page records the gap rather than publishing traced guesses. If you have this trimmer apart, the manual's own diagram is the source to work from directly.

No published torque figures for this engine. Every source we checked is under “What we found” below.

2 specs not published — flywheel nut, spark plug What we found ›

flywheel nutGAP: a figure for this exists in the Husqvarna 129-series workshop manual but only as an unlabelled number on an exploded-view diagram. It could not be tied to the flywheel nut specifically with the confidence a safety-critical fastener needs, and is deliberately not guessed at. Do not substitute the 435/445 chainsaw figure (25-30 N·m) — that is a larger, different engine.
spark plugGAP: same reason. A value in the region of 10-12 N·m appears on the diagram near the plug, but "appears near" is not a specification and it is not published here as one. For scale, Husqvarna's chainsaw manuals specify 20 N·m and Echo's M10 trimmer plug 10-15 N·m, so a trimmer figure at the lower end is plausible — which is precisely why guessing feels safe and is not.

What is the spark plug torque on a Husqvarna 440, 445 or 450 chainsaw?

20 N·m — about 15 ft-lb — stated in plain prose in Husqvarna's own workshop manual for both the 435/440e and the 445/450e. This is worth being specific about, because a figure of 18-22 ft-lb circulates widely for these saws and this page used to carry it: that is 24-30 N·m, up to 50% above Husqvarna's spec, going into a soft alloy cylinder where the failure mode is stripped threads and a cylinder replacement. Torque cold, on a clean seat. If you have no wrench that reads 15 ft-lb accurately, seat the plug against its washer finger-tight and add about a half turn.

What is the flywheel nut torque on a Husqvarna 435, 440, 445 or 450?

25-30 N·m (roughly 18-22 ft-lb). Husqvarna states it as a range, in prose: "Fit the nut on the shaft and tighten to a torque of 25-30 Nm." Use a flywheel holding tool rather than jamming the piston — a 2-stroke has no compression stroke to brake the crankshaft against, so there is nothing else stopping it turning while you tighten. The clutch is a separate fastener with its own figure.

What torque do Husqvarna guide bar nuts take?

Husqvarna does not publish one. Neither the 435/440e nor the 445/450e workshop manual contains a guide-bar-nut torque, and the 20-30 ft-lb figures that circulate for these saws — including on this page previously — have no Husqvarna document behind them. For scale, Echo specifies 20-23 N·m (about 15-17 ft-lb) for the bar nuts on a comparable saw, so the circulating numbers are high even against the nearest published equivalent. Practically: tension the chain first, tighten the two nuts evenly in an alternating pattern, then re-check tension, because tightening the nuts usually takes up slack.

Do the Husqvarna muffler bolts really need tightening twice?

Yes, and it is an explicit two-stage spec rather than a suggestion. The workshop manual gives 8-10 N·m on assembly, then a retighten to 12-14 N·m after running the saw for about a minute. The joint heat-cycles and the gasket settles on that first run, so a muffler that was correct cold is loose warm — which is how exhaust bolts back out and shear. Do the second pass.

Is the Husqvarna clutch torque a target or a minimum?

A minimum. The manual says "tightening torque min. 20 Nm" for the centrifugal clutch, which makes it the one fastener on this page where exceeding the stated figure is what Husqvarna intends rather than a mistake. Everything else — flywheel, cylinder, muffler — is a band or a target where the upper end is a limit.

Why is there no data here for the Husqvarna 128 or 129 trimmer?

Because Husqvarna publishes those specs in a form that cannot be read reliably. The 129-series workshop manual does have a "Service data" page with about 17 torque figures, but they are bare numbers pinned to an exploded-view diagram by leader lines, with no text anywhere in the document naming which fastener each belongs to. Reading them means tracing a line by eye across a diagram, and getting that wrong on a flywheel nut is how someone gets hurt. This page records the gap rather than publishing traced guesses, and it does not substitute the chainsaw figures — a 28cc trimmer is not a 45cc saw.

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