Small Engine
Honda GX390
4-Stroke
The Honda GX390 is a 389cc 4-stroke overhead-valve engine and the top model in Honda's single-cylinder GX commercial series, powering large pressure washers, high-output generators, log splitters, and construction equipment requiring sustained torque. It uses a Keihin float-type carburetor and accepts NGK BPR6ES or Champion RC12YC spark plugs. Oil quality and change intervals are critical at this displacement — Honda specifies SAE 10W-30 with changes every 100 hours. The Keihin carburetor float level and main jet are the primary fuel system service points. One of the most widely remanufactured small engines in North America.
Honda GX390 quick specs
- Equipment
- Small Engine · 4-Stroke
- Covered Parts
- Spark Plug, Air Filter, Carburetor, Recoil Starter, Ignition Coil
- OEM References
- 98079-56846, 17210-ZE3-505, 16100-ZF6-V01, 28400-ZF6-003ZA, 30500-ZF6-W31
- Model Family
- GX340, GX390
- Data Confidence
- Not yet independently reviewed
Quick Fitment
- Spark PlugOEM / Spec: 98079-56846NGK BPR6ESSearch Amazon →Affiliate link
- Air FilterOEM / Spec: 17210-ZE3-505OEM 17210-ZE3-505Search Amazon →Affiliate link
- CarburetorOEM / Spec: 16100-ZF6-V01Keihin HA-YSearch Amazon →Affiliate link
- Recoil StarterOEM / Spec: 28400-ZF6-003ZAStens 150-472Search Amazon →Affiliate link
- Ignition CoilOEM / Spec: 30500-ZF6-W31OEM 30500-ZF6-W31Search Amazon →Affiliate link
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Tune-Up Kit
Common service bundle: spark plug, air filter, carburetor.
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 Honda GX390, 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.
- Installing the correct plug number with the wrong gap.
Symptoms Map
Won't start
Spark plug, fuel filter, primer bulb, carburetor
Bogs under throttle
Air filter, carburetor, spark plug gap
Replacement Options
Best OEM equivalent
Start with OEM references 98079-56846, 17210-ZE3-505, 16100-ZF6-V01, 28400-ZF6-003ZA and match the removed part before choosing a listing.
Named part options
Cross-check named parts such as NGK BPR6ES (spark plug), Keihin HA-Y (carburetor), Stens 150-472 (recoil starter) against the OEM number, identity label, and dimensions.
Best for annual tune-up
Bundle spark plug, air filter when servicing the Honda GX390 at the start of the season.
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 Honda GX390? 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 GX390? 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
- Dimensions
- 0.7mm gap
Air Filter
- Variant notes
- Also fits GX340; different filter than GX160/GX200
- 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
- Variant notes
- Keihin HA-Y float-type carb; also fits GX340
- KeihinHA-Y
Recoil Starter
- Variant notes
- Also fits GX340
- Stens150-472
Ignition Coil
- Variant notes
- Also fits GX340
- No named part listing is published for this part yet. Use the OEM reference and verify with a dealer or service manual before ordering.