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Trimmer

Stihl FS 40

2-Stroke · Also known as: FS 40 C

The Stihl FS 40 is a 27.2cc 2-stroke curved-shaft trimmer positioned just above the FS 38 in Stihl's consumer range, with a slightly refined handlebar configuration. Suited for residential grass trimming and lawn edging. The FS 40 runs a Zama carburetor; fuel system maintenance — primer bulb, fuel filter, and fuel lines — accounts for the majority of service calls. It uses a bump-feed .080" trimmer head. The FS 38, FS 40, and FS 45 share engine and filter components, ensuring strong parts availability across the entire entry range.

Verify before ordering: Fitment can vary by serial number, production date, region, and sub-model. Match the OEM number and physical dimensions before ordering.

Stihl FS 40 quick specs

Equipment
Trimmer · 2-Stroke
Covered Parts
Spark Plug, Air Filter, Fuel Filter, Carburetor, Primer Bulb, Fuel Line Kit, Trimmer Head, Trimmer Line
OEM References
0000 400 7000, 4144 124 2800, 0000 350 3502, 4144 120 0608, 4226 121 2700, 4144 358 0800, 4006 710 2126
Model Family
FS 38, FS 40, FS 45, FS 55
Data Confidence
Not yet independently reviewed

Quick Fitment

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Tune-Up Kit

Common service bundle: spark plug, air filter, fuel filter, carburetor, primer bulb, fuel line kit.

Maintenance Interval

Inspect filters and fuel lines each season, replace spark plugs during annual service, and service carb/fuel-system parts when starting or idle symptoms appear.

Before You Buy

  • Confirm the full model is Stihl FS 40, not just the family name.
  • Check serial number, production date, and regional variant before ordering.
  • Match the old OEM number stamped on the removed part when available.
  • Compare dimensions, plug gap, thread, fuel line diameter, or chain pitch/gauge where applicable.

Common Mistakes

  • Ordering from a family listing without checking the exact sub-model.
  • Buying a kit that includes the headline part but wrong gaskets, lines, or bulb size.
  • Choosing the wrong carburetor revision when multiple versions were used.
  • Assuming all fuel line kits use the same diameter and routing.
  • Installing the correct plug number with the wrong gap.

Symptoms Map

Won't start

Spark plug, fuel filter, primer bulb, carburetor

Starts then dies

Fuel filter, fuel line kit, carburetor

Bogs under throttle

Air filter, carburetor, spark plug gap

Primer will not fill

Primer bulb, fuel line routing, in-tank filter

Replacement Options

Best OEM equivalent

Start with OEM references 0000 400 7000, 4144 124 2800, 0000 350 3502, 4144 120 0608 and match the removed part before choosing a listing.

Named part options

Cross-check named parts such as NGK BPMR7A (spark plug), Zama C1M-S267D (carburetor), Zama 0057004 (primer bulb) against the OEM number, identity label, and dimensions.

Best for annual tune-up

Bundle spark plug, air filter, fuel filter when servicing the Stihl FS 40 at the start of the season.

Best if replacing fuel system

Compare the fuel filter, carburetor, primer bulb, fuel line kit together so line routing, bulb size, filter style, and carburetor connections match.

Best budget kit

Use kit listings only when every included part matches this model page; cheap kits often mix correct headline parts with wrong bulbs, lines, or gaskets.

FAQ

Should I buy OEM or aftermarket parts for the Stihl FS 40? Use OEM when the part controls fuel metering, ignition, or safety. Aftermarket kits can be useful for routine filters, bulbs, plugs, and tune-up bundles when the OEM number and dimensions match.

How do I avoid ordering the wrong carburetor for the FS 40? Match the carburetor number stamped on the removed unit, then compare linkage, choke setup, primer routing, gasket stack, and fuel-inlet direction.

What should I check before replacing fuel-system parts? Photograph the old fuel-line routing, match line diameter and filter style, and compare primer bulb size before buying a kit.

As an Amazon Associate, WhichPartFits earns from qualifying purchases. Match the OEM number, dimensions, and model variant before buying.

Spark Plug

OEM0000 400 7000
Dimensions
0.7mm gap

Air Filter

OEM4144 124 2800
Variant notes
Also fits FS 50, FS 70, KM 56
  • No named part listing is published for this part yet. Use the OEM reference and verify with a dealer or service manual before ordering.

Fuel Filter

OEM0000 350 3502
Variant notes
3/16" ID in-tank filter
  • No named part listing is published for this part yet. Use the OEM reference and verify with a dealer or service manual before ordering.

Carburetor

OEM4144 120 0608
Variant notes
Zama C1M-S267D; also fits FS 50, FS 56

Primer Bulb

OEM4226 121 2700

Fuel Line Kit

OEM4144 358 0800
Variant notes
Includes fuel pickup line and return line; also fits FS 50, FS 56, FS 70

Trimmer Head

OEM4006 710 2126
Variant notes
AutoCut C 6-2; bump-feed; .080" line

Trimmer Line

OEMSpec-based fitment
Dimensions
.080" diameter, round