Small Engine
Briggs & Stratton 550ex Series
4-Stroke
The Briggs & Stratton 550EX is a 159cc 4-stroke overhead-valve engine used in upper entry-level consumer push mowers. The EX designation indicates an enhanced engine series with ReadyStart. It uses a Walbro or Nikki carburetor and a Champion RC12YC spark plug. At this displacement, the 550EX handles medium-density residential turf reliably. Annual maintenance: oil change (SAE 30 or 10W-30), air filter replacement, and spark plug inspection. The carburetor diaphragm and main jet are the primary fuel system service points. The most common engine on mid-range consumer push mowers sold at home improvement stores.
Briggs & Stratton 550ex Series quick specs
- Equipment
- Small Engine · 4-Stroke
- Covered Parts
- Spark Plug, Air Filter, Carburetor, Primer Bulb, Fuel Filter
- OEM References
- 796112S, 593260, 799584, 694394, 298090S
- Model Family
- 450e Series, 500e Series, 550ex Series, 625ex Series, 675ex Series
- Last Reviewed
- Not yet independently reviewed
- Data Confidence
- Not yet independently reviewed
- Sources Consulted
- Evidence source not recorded
Quick Fitment
| Part Type | OEM / Spec | Common Option | Confidence |
|---|---|---|---|
| Spark Plug | 796112S | Champion RC12YC | Confidence not assigned · Not yet independently reviewed |
| Air Filter | 593260 | Stens 100-959 | Confidence not assigned · Not yet independently reviewed |
| Carburetor | 799584 | Briggs & Stratton 594058 | Confidence not assigned · Not yet independently reviewed |
| Primer Bulb | 694394 | Stens 120-730 | Confidence not assigned · Not yet independently reviewed |
| Fuel Filter | 298090S | Stens 120-436 | Confidence not assigned · Not yet independently reviewed |
Tune-Up Kit
Common service bundle: spark plug, air filter, carburetor, primer bulb, fuel filter.
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 Briggs & Stratton 550ex Series, 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
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 796112S, 593260, 799584, 694394 and match the removed part before choosing a listing.
Common aftermarket option
Cross-check aftermarket listings such as Champion RC12YC (spark plug), Stens 100-959 (air filter), Briggs & Stratton 594058 (carburetor) against the OEM number and dimensions.
Best for annual tune-up
Bundle spark plug, air filter, fuel filter when servicing the Briggs & Stratton 550ex Series at the start of the season.
Best if replacing fuel system
Compare the carburetor, primer bulb, fuel filter 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 Briggs & Stratton 550ex Series? 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 550ex Series? 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.
Spark Plug
- Reviewed
- Not yet independently reviewed
- Dimensions
- 0.030" gap
- Variant notes
- Powers mid-range push mowers including Troy-Bilt TB110, TB130, and Craftsman M105 with 140cc engines
Air Filter
- Reviewed
- Not yet independently reviewed
- Variant notes
- Paper cartridge element; replaces 798452 and 334404. Fits 09P702 series engines. Pre-cleaner foam sold separately.
| Brand | Part # | |
|---|---|---|
| Stens | 100-959 | Some links may be affiliate links. Match the OEM number, dimensions, and model variant before buying. |
Carburetor
- Reviewed
- Not yet independently reviewed
- Variant notes
- For 09P702 series 140cc engines. Also replaces 592361, 594057, 594058, 594529. Used on Troy-Bilt TB110, TB200.
| Brand | Part # | |
|---|---|---|
| Briggs & Stratton | 594058 | Some links may be affiliate links. Match the OEM number, dimensions, and model variant before buying. |
Primer Bulb
- Reviewed
- Not yet independently reviewed
- Variant notes
- Fits all 450–675 series Briggs & Stratton small engines. DIY packaged version is 5084K.
| Brand | Part # | |
|---|---|---|
| Stens | 120-730 | Some links may be affiliate links. Match the OEM number, dimensions, and model variant before buying. |
Fuel Filter
- Reviewed
- Not yet independently reviewed
- Variant notes
- 150-micron inline fuel filter for 1/4" fuel line; for engines without a fuel pump. DIY packaged version is 5018K.
| Brand | Part # | |
|---|---|---|
| Stens | 120-436 | Some links may be affiliate links. Match the OEM number, dimensions, and model variant before buying. |