Chainsaw

Husqvarna 450

2-Stroke

The Husqvarna 450 is a 50.1cc 2-stroke chainsaw at the top of Husqvarna's homeowner range, suited for demanding firewood production, regular felling, and prosumer land management with 18" to 20" guide bars. It runs a Zama carburetor and features the X-Torq engine with Air Injection pre-cleaning. The 450 shares service parts families with the 455 Rancher. Common maintenance items are the spark plug, air filter, fuel filter, primer bulb, and bar oiler. A popular step-up from the 445 for users who regularly fell trees larger than 12" in diameter.

See a wrong fitment? Report a correction.

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

Equipment: Chainsaw · 2-Stroke
Covered Parts: Spark Plug, Air Filter, Fuel Filter, Carburetor, Ignition Coil, Primer Bulb, Fuel Line Kit, Chain, Guide Bar
OEM References: 537254402, 531009748, 503446501, 545070601, 544454801, 503936601, 544128601
Model Family: 445, 450, 455 Rancher
Last Reviewed: 2026-05-20
Data Confidence: Aftermarket-confirmed
Sources Consulted: OEM part references, Aftermarket catalog cross-references, Retailer fitment listings

ℹ See also: 445, 455 Rancher — parts are often interchangeable within this family.

Quick Fitment

Part Type	OEM / Spec	Common Option	Confidence
Spark Plug	537254402	NGK BPMR7A	Medium · 2026-05-20
Air Filter	531009748	Stens 605-414	Medium · 2026-05-20
Fuel Filter	503446501	Stens 610-035	Medium · 2026-05-20
Carburetor	545070601	Zama C1Q-EL24A	Medium · 2026-05-20
Primer Bulb	503936601	Zama BG-00-4	Medium · 2026-05-20
Ignition Coil	544454801	OEM 544454801	Low · 2026-05-20
Fuel Line Kit	544128601	Stens 115-627	Medium · 2026-05-20
Chain	20", .325" pitch, .050" gauge, 78 drive links	Oregon 20BPX078G	Low · 2026-05-20

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 Husqvarna 450, 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.
Matching bar length but missing pitch, gauge, or drive-link count.

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

Cuts slowly

Chain pitch/gauge, bar wear, drive links

Replacement Options

Best OEM equivalent

Start with OEM references 537254402, 531009748, 503446501, 545070601 and match the removed part before choosing a listing.

Common aftermarket option

Cross-check aftermarket listings such as NGK BPMR7A (spark plug), Stens 605-414 (air filter), Stens 610-035 (fuel filter) against the OEM number and dimensions.

Best for annual tune-up

Bundle spark plug, air filter, fuel filter when servicing the Husqvarna 450 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 chain/bar combo

Match chain specs together, especially pitch, gauge, drive links, and bar mount details.

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

Does this fit 445 or 455 Rancher? Parts may interchange with 445, 455 Rancher, but verify the serial range, OEM number, and physical part details before ordering.

Should I buy OEM or aftermarket parts for the Husqvarna 450? 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 450? 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.

What chain details matter besides bar length? Match pitch, gauge, and drive-link count against the bar stamp, old chain, and drive sprocket. Bar length alone is not enough.

Spark Plug

OEM537254402Confidence: Medium · Source: Aftermarket catalog

Reviewed: 2026-05-20
Dimensions: 0.5mm gap

Brand	Part #
NGK	BPMR7A	Best for annual tune-upAmazonAffiliate link Some links may be affiliate links. Match the OEM number, dimensions, and model variant before buying.
Champion	RCJ7Y	Best for annual tune-upAmazonAffiliate link Some links may be affiliate links. Match the OEM number, dimensions, and model variant before buying.

Air Filter

OEM531009748Confidence: Medium · Source: Aftermarket catalog

Reviewed: 2026-05-20
Variant notes: Fits 450 and 450e

Brand	Part #
Stens	605-414	Best for annual tune-upAmazonAffiliate link Some links may be affiliate links. Match the OEM number, dimensions, and model variant before buying.

Fuel Filter

OEM503446501Confidence: Medium · Source: Aftermarket catalog

Reviewed: 2026-05-20

Brand	Part #
Stens	610-035	Best if replacing fuel systemAmazonAffiliate link Some links may be affiliate links. Match the OEM number, dimensions, and model variant before buying.

Carburetor

OEM545070601Confidence: Medium · Source: Aftermarket catalog

Reviewed: 2026-05-20
Variant notes: Zama C1Q-EL24A

Brand	Part #
Zama	C1Q-EL24A	Best if replacing fuel systemAmazonAffiliate link Some links may be affiliate links. Match the OEM number, dimensions, and model variant before buying.

Ignition Coil

OEM544454801Confidence: Low · Source: Aftermarket catalog

Reviewed: 2026-05-20
Variant notes: Also fits 435, 440

Brand	Part #
No aftermarket listing is published for this part yet. Use the OEM reference and verify with a dealer or service manual before ordering.

Primer Bulb

OEM503936601Confidence: Medium · Source: Aftermarket catalog

Reviewed: 2026-05-20

Brand	Part #
Zama	BG-00-4	Best if replacing fuel systemAmazonAffiliate link Some links may be affiliate links. Match the OEM number, dimensions, and model variant before buying.

Fuel Line Kit

OEM544128601Confidence: Medium · Source: Aftermarket catalog

Reviewed: 2026-05-20
Variant notes: Includes fuel pickup line and return line

Brand	Part #
Stens	115-627	Best if replacing fuel systemAmazonAffiliate link Some links may be affiliate links. Match the OEM number, dimensions, and model variant before buying.

Chain

OEMSpec-based fitmentConfidence: Low · Source: Inferred

Reviewed: 2026-05-20
Dimensions: 20", .325" pitch, .050" gauge, 78 drive links
Variant notes: Stock bar length; verify drive link count matches your bar

Brand	Part #
Oregon	20BPX078G	Best chain/bar comboAmazonAffiliate link Some links may be affiliate links. Match the OEM number, dimensions, and model variant before buying.

Guide Bar