(Pack of 2) 491055 491055S Spark Plug Compatible with Champion RC12YC RC12YX Briggs and Stratton 491055T 692051 792015 5066 Lawn Mower Engine

What It Is

This is a pack of two aftermarket spark plugs (model 491055/491055S) designed to replace Champion RC12YC, RC12YX, and several Briggs & Stratton OEM plugs (491055T, 692051, 792015, 5066). They’re intended for small engines in lawn mowers, tractors, generators, and pressure washers.

Fitment & Compatibility

• Check your engine’s OEM plug number – This plug cross-references to Champion RC12YC and RC12YX, and Briggs & Stratton 491055T, 692051, 792015, 5066. Confirm your engine manual or old plug matches one of these.
• Thread size & reach – Standard 14mm thread, 19mm (3/4") reach. Measure your old plug’s threaded length; too short or too long can cause misfire or piston damage.
• Gap – Factory gap is typically 0.030" (0.76mm). Always verify and adjust with a gap tool before installing. Not pre-gapped.
• Brand note – These are aftermarket (not OEM Briggs or Champion). Quality varies; inspect ceramic insulator for cracks or chips.

Key Things to Know

• Installation difficulty – Easy. Remove spark plug wire, unscrew old plug with a 5/8" socket, gap new plug, hand-tighten, then torque to 20 ft-lbs (or 1/4 turn past snug). Over-tightening can strip threads.
• Common gotcha – The “S” in 491055S often means “Service” (same specs). Don’t confuse with different heat ranges (e.g., RC12YC vs RC14YC).
• Quality note – At $4.50 per plug, these are budget replacements. They may not last as long as OEM Champion or NGK plugs (which cost ~$6–8 each). Fine for seasonal use, but expect shorter lifespan in high-hour engines.
• Two-pack value – Handy if you have a two-cylinder engine (e.g., some riding mowers) or want a spare. Single packs are often similar price.

Should You Buy It

Buy this if you need a quick, low-cost replacement for a Briggs or small engine mower and don’t mind aftermarket quality. It’s a good budget option for occasional use or as a backup. Skip if you want maximum durability or have a high-performance engine—spend a few extra dollars on an OEM Champion RC12YC or NGK BPR6ES.