Carburetor, Muffler & Blower Housing Torque Specs

Head bolts and flywheel nuts get all the attention, but the fasteners you actually strip are the small ones: the carburetor studs you back off to clean a bowl, the sheet-metal screws holding the blower housing, the muffler nuts that shear because nobody torqued them. This page pulls every published service-hardware figure out of the Honda, Kohler, Kawasaki, Briggs & Stratton, Stihl, Husqvarna and Echo manuals and sorts them by component instead of by engine — so you can compare what seven manufacturers say about the same joint, and find a defensible number when your own manual is silent. The handheld 2-stroke rows are worth reading against the 4-stroke ones: they show how far apart the same-sounding fastener can be, and a figure borrowed across that gap is the most common way one of these joints gets ruined.

Where these numbers come from: Nothing here is a new number. Every row is the same object rendered on the engine-specific page it came from, carrying its original manufacturer PDF as its source — Kohler service forms 17/20/24/32 690 xx, the Kawasaki FR/FS/FX/FH/FJ manuals, Honda's GX reference sheets, the Briggs Vanguard tables, the Stihl dealer service manuals, Husqvarna's 435-450 workshop manuals and Echo's first-party service and operator manuals. Where a manufacturer publishes no value, the row says so rather than borrowing one from another brand.

Carburetor fuel bowl & float chamber

The screw at the bottom of the bowl. It threads into thin cast alloy and is the single most-stripped fastener on a small engine — the values below are why "just snug it" ruins carburetors.

Component	Torque	Thread	Confidence	Notes
Kohler Courage SV470-SV620 — carburetor fuel bowl screw, Walbro	45–55 in-lb	—	high	5.1-6.2 N·m, as printed by Kohler. This is the most-stripped fastener on the engine — the low end of the band is the number to aim at, not the high one.
Kohler Courage SV470-SV620 — carburetor fuel bowl screw, Nikki	96–113 in-lb	—	high	10.8-12.8 N·m, as printed by Kohler. Nikki-equipped carbs torque noticeably higher than Walbro on this platform — check your carb brand before assuming a value.
Kawasaki FJ180V — carburetor float chamber mounting bolt	48 in-lb	—	high	5.4 N-m (0.55 kgf-m).

Carburetor mounting studs, screws & nuts

What holds the carb to the intake. Over-torquing here crushes the insulator block and gasket, which causes the lean-run/surging that sends people back to buy another carburetor they did not need.

Component	Torque	Thread	Confidence	Notes
Kohler Command PRO CH395 — carburetor mounting stud	7.4 ft-lb	—	high	10 N·m (89 in-lb). Primary nut on the stud torques to 8 N·m (71 in-lb / 5.9 ft-lb).
Kohler Command CH620-CH750 V-Twin (CH640, CH680, CH730, CH740) — carburetor mounting screw (M6)	55–65 in-lb	M6	high	6.2-7.3 N·m. Kohler prints this as a band in in-lb; both ends are shown rather than the upper bound alone.
Kohler Command CV620-CV750 V-Twin (CV640, CV680, CV730, CV740) — carburetor mounting nut (M6)	55–65 in-lb	M6	high	6.2-7.3 N·m, as printed by Kohler. Called "Mounting Nut" in the CV manual vs "Mounting Screw" in the CH manual.
Kohler 7000 Series (KT715-KT745) — carburetor mounting nut	55–65 in-lb	—	high	6.2-7.3 N·m, as printed by Kohler.
Kawasaki FR651V / FR691V / FR730V / FS651V / FS691V / FS730V / FX651V / FX691V / FX730V — carburetor and inlet pipe mounting bolt/nut	52 in-lb	—	high	5.9 N-m (0.60 kgf-m).
Kawasaki FX801V / FX850V — carburetor and inlet pipe mounting bolt/nut	52 in-lb	—	high	5.9 N-m (0.60 kgf-m).
Stihl MS 210 / MS 230 / MS 250 — filter housing / carburetor	24 in-lb	M5 collar locknut	high	2.7 N·m.

Intake manifold & inlet pipe

The manifold between carburetor and head. A loose one is the classic hunting/surging air leak; an over-torqued one warps the flange and creates the same symptom.

Component	Torque	Thread	Confidence	Notes
Briggs & Stratton Vanguard OHV V-Twin — intake manifold	140 in-lb	—	high	16.0 N-m equivalent.
Kohler Command CH620-CH750 V-Twin (CH640, CH680, CH730, CH740) — intake manifold mounting fastener (2-stage)	7.3 ft-lb	—	high	Final 9.9 N·m (88 in-lb); initial 7.4 N·m (66 in-lb).
Kohler Command CV620-CV750 V-Twin (CV640, CV680, CV730, CV740) — intake manifold mounting fastener (2-stage)	7.3 ft-lb	—	high	Final 9.9 N·m (88 in-lb); initial 7.4 N·m (66 in-lb).
Kohler 7000 Series (KT715-KT745) — intake manifold mounting fastener (2-stage)	7.3 ft-lb	—	high	Final 9.9 N·m (88 in-lb); initial 7.4 N·m (66 in-lb).
Kawasaki FR651V / FR691V / FR730V / FS651V / FS691V / FS730V / FX651V / FX691V / FX730V — inlet manifold mounting bolt	52 in-lb	—	high	5.9 N-m (0.60 kgf-m). Sequence torque (remarks code "S").
Kawasaki FR541V / FR600V / FS481V / FS541V / FS600V / FX600V — control panel / intake pipe mounting bolt	52 in-lb	—	high	5.9 N-m (0.60 kgf-m).
Kawasaki FR541V / FR600V / FS481V / FS541V / FS600V / FX600V — intake manifold mounting bolt (FR models)	78 in-lb	—	high	8.8 N-m (0.90 kgf-m). Sequence torque (remarks code "S"). FR541V/FR600V use a different intake-manifold bolt torque than the FS/FX models sharing this manual -- see next row.
Kawasaki FR541V / FR600V / FS481V / FS541V / FS600V / FX600V — intake manifold mounting bolt (FS and FX models)	52 in-lb	—	high	5.9 N-m (0.60 kgf-m). Sequence torque (remarks code "S").

Blower housing & sheet metal screws

The recoil/shroud screws you remove to reach anything else. Most thread directly into aluminium bosses, which is why several manuals publish a lower figure for a hole that has already been used once.

Component	Torque	Thread	Confidence	Notes
Kohler Command PRO CH395 — blower housing / sheet metal screw	7.4 ft-lb	M6	high	10 N·m (89 in-lb).
Kohler Command PRO CH440 — blower housing / sheet metal screw	7.4 ft-lb	M6	high	10 N·m (89 in-lb).
Kohler 7000 Series (KT715-KT745) — blower housing / sheet metal M6 fastener	7.9 ft-lb	M6	high	10.7 N·m (95 in-lb) into a new hole; 7.3 N·m (65 in-lb / 5.4 ft-lb) into a used hole.
Kohler Courage SV470-SV620 — blower housing / sheet metal M6 fastener	8.3 ft-lb	M6	high	11.6 N·m (99 in-lb) into a new hole; 7.7 N·m (68 in-lb / 5.7 ft-lb) into a used hole.

Muffler & exhaust hardware

Heat-cycled and usually rusted, and the ones most likely to shear on removal. Read the unit column carefully here: the 4-stroke M8 muffler nuts are an 18 ft-lb job, while the handheld 2-stroke rows below them are in-lb — Stihl's spark-arresting screen is 9 in-lb, about a hundredth of the figure a few rows up. Nowhere on this site do two fasteners with such similar names sit so far apart.

Component	Torque	Thread	Confidence	Notes
Honda GX160 — muffler nut	18 ft-lb	M8x1.25	high	24 N-m / 2.4 kgf-m.
Briggs & Stratton Vanguard OHV V-Twin — exhaust manifold	150 in-lb	—	high	17.0 N-m equivalent.
Kohler Command PRO CH395 — muffler exhaust screw	Not published	—		GAP: the manual's Muffler Exhaust Screw row is split into an M8 column (24 N·m/212 in-lb) and an M10 column (35 N·m/310 in-lb), but the manual's table doesn't unambiguously assign the M8 vs M10 column to the CH395 specifically (M10/35 N·m is confirmed for CH440 — see that engine's row). No CH395-specific number is asserted without a clearer copy of the source table.
Kohler Command PRO CH440 — muffler exhaust screw	25.8 ft-lb	M10	high	35 N·m (310 in-lb), M10.
Kohler Command CH620-CH750 V-Twin (CH640, CH680, CH730, CH740) — muffler M8 hex nuts	18 ft-lb	M8	high	24.4 N·m (216 in-lb). Lock-nut variant torques higher, to 27.8 N·m (246 in-lb / 20.5 ft-lb).
Kohler Command CV620-CV750 V-Twin (CV640, CV680, CV730, CV740) — muffler retaining nuts	18 ft-lb	—	high	24.4 N·m (216 in-lb). The CV manual gives one undifferentiated value; unlike the CH manual it does not separately list a lock-nut variant — thread size (M8) is also not stated here, unlike the CH manual's explicit M8 callout.
Kohler 7000 Series (KT715-KT745) — muffler M8 hex nuts	18 ft-lb	M8	high	24.4 N·m (216 in-lb). Lock-nut variant 27.8 N·m (246 in-lb / 20.5 ft-lb); 5/16-18 capscrew variant 16.9 N·m (150 in-lb / 12.5 ft-lb) depending on cylinder-head design.
Kohler Courage SV470-SV620 — muffler retaining nuts	18 ft-lb	—	high	24.4 N·m (216 in-lb). Bracket screw torques lower, to 7.5 N·m (65 in-lb / 5.4 ft-lb).
Kawasaki FR651V / FR691V / FR730V / FS651V / FS691V / FS730V / FX651V / FX691V / FX730V — muffler / exhaust mount	Not published	—		GAP: no muffler or exhaust-flange torque value is listed anywhere in this manual for the FR/FS/FX 651V-730V family -- the muffler is equipment-manufacturer-supplied on these mower engines, not a Kawasaki-specified fastener.
Kawasaki FR541V / FR600V / FS481V / FS541V / FS600V / FX600V — muffler / exhaust mount	Not published	—		GAP: no muffler or exhaust-flange torque value is listed in this manual for the FR541V/FR600V/FS481-600V/FX481-600V family.
Kawasaki FX801V / FX850V — muffler / exhaust mount	Not published	—		GAP: no muffler or exhaust-flange torque value is listed in this manual for the FX751V/FX801V/FX850V family -- equipment-OEM supplied.
Kawasaki FJ180V — muffler cover self-tap bolt	61 in-lb	—	high	6.9 N-m (0.70 kgf-m).
Kawasaki FH580V — exhaust pipe flange nut (muffler mount)	11 ft-lb	—	high	15 N-m (1.5 kgf-m).
Kawasaki FH601V / FH680V — exhaust pipe flange nut (muffler mount)	11 ft-lb	—	high	15 N-m (1.5 kgf-m).
Stihl MS 210 / MS 230 / MS 250 — muffler	71 in-lb	M5 collar locknut	high	8 N·m.
Stihl MS 261 / MS 261 C — muffler to crankcase	89 in-lb	M5x16	high	10.0 N·m.
Stihl MS 261 / MS 261 C — muffler to cylinder	89 in-lb	M5x16	high	10.0 N·m.
Stihl MS 261 / MS 261 C — spark arresting screen to muffler	9 in-lb	M4x9.6	high	1.0 N·m. The lowest figure on the saw — this is a screwdriver-feel fastener, and no ft-lb wrench will read it.
Stihl MS 271 C / MS 291 C — muffler to cylinder	80 in-lb	D5x18	high	9.0 N·m.
Stihl FS 45 trimmer — stub to muffler	11 ft-lb	M14x1.25	high	15.0 N·m, printed by Stihl as 11.0 lbf-ft. Install with sealant.
Stihl FS 45 trimmer — muffler to cylinder	80 in-lb	IS-DG5x60 spline	high	9.0 N·m, printed by Stihl as 6.6 lbf-ft.
Husqvarna 435 / 435e / 440e — muffler bolt, initial	71–89 in-lb	—	high	8-10 N·m. This is a two-stage spec — see the retighten row below; stopping at this figure is not the finished job.
Husqvarna 435 / 435e / 440e — muffler bolt, retighten after run-in	106–124 in-lb	—	high	12-14 N·m, applied after running the saw for about a minute so the joint has heat-cycled once.
Husqvarna 445 / 445e / 450e — muffler bolt, initial	71–89 in-lb	—	high	8-10 N·m. Two-stage spec — see the retighten row.
Husqvarna 445 / 445e / 450e — muffler bolt, retighten after run-in	106–124 in-lb	—	high	12-14 N·m, after about a minute of running.
Echo SRM-2620ES / SRM-2620TES — muffler	62–97 in-lb	M5	high	7-11 N·m (70-110 kgf-cm).
Echo SRM-2620ES / SRM-2620TES — muffler cover, crankcase side	27–40 in-lb	M5	high	3-4.5 N·m (30-45 kgf-cm). Note this differs from the starter-side cover screw below — Echo gives the two sides different figures.
Echo SRM-2620ES / SRM-2620TES — muffler cover, starter side	22–31 in-lb	M5	high	2.5-3.5 N·m (25-35 kgf-cm). The lowest figure in the table.
Echo CS-400 — muffler mounting bolt / nut	70–95 in-lb	—	high	8-11 N·m. Two-stage: tighten cold, then re-tighten after the saw has warmed up.
Echo CS-590 Timber Wolf — muffler mounting bolt / nut	Not published	—		GAP: the CS-590 operator's manual prints no muffler-bolt torque, although the CS-400's does (8-11 N·m). The CS-400 figure is not carried over here — same brand is not the same engine, and this is a 59.8cc saw against a 40.2cc one.
Echo SRM-225 trimmer — muffler mounting bolt / nut	80–95 in-lb	—	high	90-110 kgf-cm as printed, which converts to 9.0-10.7 N·m. Two-stage: tighten, run, re-tighten.

My manual does not list a carburetor mounting torque. What should I use?

Compare the published values first: Kohler specifies 55–65 in-lb for the M6 carburetor mounting screw/nut across the CH620–CH750, CV620–CV750 and 7000 Series, and Kawasaki specifies 52 in-lb for the carburetor and inlet-pipe mounting bolt on the FR/FS/FX families. Four separate manuals landing in a 52–65 in-lb band on the same joint is a strong signal, so an unlisted M6 carburetor mounting screw or nut in that class is unlikely to want much more than 65 in-lb. Two cautions. That is an inference, not a specification — if your engine publishes a number, that number wins. And do not confuse the nut with the stud: on the CH395 the figure for driving the mounting stud into the block is 89 in-lb, while the nut that actually clamps the carburetor onto that stud is 71 in-lb. They are different fasteners doing different jobs.

Why does Kohler give two different blower housing torques for the same screw?

Because the thread is cut by the screw itself. On the 7000 Series the sheet-metal M6 fastener torques to 95 in-lb going into a new hole but only 65 in-lb into a used one; the Courage SV470–SV620 does the same thing at 99 in-lb new versus 68 in-lb used. The first install forms the thread in soft aluminium and takes the higher figure; every reinstall after that is into an already-formed thread that will strip at the original number. If you have taken the shroud off before, use the lower value.

Is there a common muffler bolt torque for small engines?

It tracks thread size rather than brand. Honda specifies 18 ft-lb for the M8x1.25 muffler nut on the GX160, and Kohler independently specifies 18 ft-lb for the M8 muffler hex nuts on the CH620–CH750 and the 7000 Series — two manufacturers, same thread, same number. Step up to M10 and Kohler's CH440 muffler exhaust screw goes to 25.8 ft-lb. Match the thread, not the badge. One caveat on lock nuts: where Kohler lists a lock-nut variant it torques higher, to 20.5 ft-lb. And do not carry any of that onto a chainsaw or trimmer: those mufflers are M5, and Stihl, Husqvarna and Echo all specify them in the 8-11 N·m band — 71 to 97 in-lb, roughly a fifth of the 4-stroke M8 figure. Two of them also specify it in two stages, tightened cold then retightened after a run, which no 4-stroke manual here does.

Why does Kawasaki publish no muffler torque at all?

Because on the FR, FS and FX mower engines the muffler is not a Kawasaki part. It is supplied by whoever built the mower, so the torque belongs in the equipment manufacturer's manual rather than Kawasaki's. The rows on this page say "not published" instead of showing a figure borrowed from another brand — if you need that number, look up the mower, not the engine.

Does the carburetor fuel bowl screw really need a torque wrench?

It is the fastener most worth one. Kohler's Courage SV470–SV620 manual specifies 45–55 in-lb for a Walbro fuel bowl screw but 96–113 in-lb for a Nikki — the same job on the same engine family, roughly double the torque, depending only on which carburetor is fitted. Guessing means either weeping fuel or a stripped bowl, and you cannot tell which carburetor you have by feel. Check the brand stamped on the bowl before you touch it.

These are in-lb and my torque wrench is in ft-lb. Can I still use it?

Not for most of this page. The carburetor, fuel-bowl and sheet-metal rows sit between roughly 50 and 115 in-lb — that is 4–10 ft-lb, the very bottom of a 3/8" ft-lb click wrench's range, where it is least accurate and usually below its minimum setting entirely. Those want a dedicated in-lb wrench. Only the heavy exhaust hardware is genuinely in ft-lb territory: the M8 muffler nuts at 18 ft-lb, Kohler's M10 exhaust screw at 25.8 ft-lb, and the Kawasaki exhaust flange nuts at 11 ft-lb. Everything else on this page — including the intake fasteners at 52 to 140 in-lb (about 4–12 ft-lb) and the Kawasaki muffler cover bolt at 61 in-lb — is still an in-lb job, and a 20–200 in-lb wrench covers all of it.

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