491055 491055S Spark Plugs for Briggs and Stratton 491055T 805015 499608 694385 5066 Champion RC12YC RC12YX 759-3336 Lawn Mower Engine (Pack of 1) Review

Overview

This isn’t a lawn mower—it’s a spark plug. Specifically, the 491055 (and its 491055S variant) is a direct replacement for Briggs & Stratton engines found on countless walk-behind mowers, riding tractors, and pressure washers. It’s designed for anyone who needs a reliable, drop-in fix for a hard-starting or misfiring engine without hunting through cross-reference charts. At $7.39, it’s a budget-friendly way to restore performance to small engines from brands like Toro, Craftsman, Husqvarna, and John Deere.

Who Should Buy This

1. Homeowners with a single mower – If you’ve got a Briggs & Stratton-powered push mower that’s been cranky to start or running rough, this plug is a cheap, 10-minute fix that can save you a service call.

2. DIY lawn equipment tinkerers – If you maintain multiple engines (mower, trimmer, pressure washer) and already know how to gap and install a spark plug, this is a no-brainer stock-up item. It fits a huge range of B&S single-cylinder engines.

3. Owners of older mowers – Many older walk-behinds and riders use the 491055/Champion RC12YC cross. If your mower is 5-10 years old and hasn’t had a plug change, this is the exact part you need.

4. Budget-minded buyers – At under $8, it’s cheaper than most auto parts store equivalents, and you’re getting a genuine-spec plug (not a no-name knockoff).

Key Features Breakdown

• Replaces OEM Part Numbers 491055, 491055S, 491055T, 805015, 499608, 694385, 5066 – This is the compatibility list that matters. If your mower’s manual calls for any of these numbers (common on B&S Intek, Quantum, and Classic engines), this plug is a direct fit. No adapters, no filing.

• Cross-Reference to Champion RC12YC and RC12YX – These are among the most common small-engine plugs on the market. If you’ve ever bought a Champion RC12YC at an auto parts store, this is the same thing, often at a lower price. The RC12YX variant has a slightly different heat range for specific B&S engines—this plug covers both.

• Pack of 1 – Some buyers wish for a 2-pack, but for a single engine, one plug is all you need. At this price, you can buy two and have a spare.

• Pre-gapped (typically 0.030 inches) – Most arrive ready to install, but always check the gap with a feeler gauge. B&S spec is usually 0.030”, but verify your engine manual. This plug’s design allows easy adjustment.

• Copper core electrode – Standard for small engines. Copper conducts heat well and provides reliable spark, though it wears faster than platinum or iridium. For a mower that sees 20-30 hours per season, you’ll get 2-3 years out of it.

Pros

1. Exact OEM fit – No guessing. If your engine takes a 491055, this plug screws in perfectly, with the right thread length (3/8”) and hex size (13/16”). No cross-threading worries if you’re careful.

2. Restores starting reliability instantly – The most common complaint with old plugs is hard starting. Swapping to this fresh plug often fixes “crank but no fire” issues on the first pull.

3. Works on multiple brands – Fits Briggs & Stratton engines on Toro, Craftsman, Husqvarna, Snapper, Murray, and many others. One plug covers a fleet of equipment.

4. Cheaper than dealer parts – A Briggs dealer might charge $10-12 for the same plug. At $7.39, you’re saving 30-40% with no loss in quality.

5. Simple installation – No special tools beyond a socket wrench and gap gauge. Even a first-timer can do it in 10 minutes with a YouTube video.

6. Solid build quality – Reviews (4.8/5 from 5 ratings) suggest consistent performance. No reports of cracked porcelain or loose threads, which can happen with ultra-cheap plugs.

Cons

1. Only one plug in the pack – If you have two engines that use the same plug, you’ll need to buy two. A twin-pack would be more convenient for multi-engine owners.

2. Not for all B&S engines – Some newer B&S models (like the 850 series) use a different plug (e.g., 796560). Double-check your engine’s spec before ordering. This plug is common but not universal.

3. Copper core wears faster than iridium – If you mow 2+ acres weekly, you might need to replace this annually. For most homeowners, it’s fine, but heavy users might prefer a longer-life option.

4. No anti-seize or dielectric grease included – A small tube of anti-seize would be nice for aluminum heads (common on B&S engines). You’ll need to buy that separately if you want to prevent corrosion.

Bottom Line

If your Briggs & Stratton engine is hard-starting, misfiring, or just due for maintenance, this 491055 spark plug is the right part at the right price. It’s a direct replacement for a huge range of mowers and small equipment, and at $7.39, it’s cheaper than most auto parts stores without sacrificing quality. The only catch is verifying your engine’s exact part number—if it matches, buy it. For homeowners with one or two B&S-powered machines, this is a no-brainer. For pros with a dozen engines, consider buying a few to keep on hand. Skip if you need a different plug type or want a multi-pack.

Frequently Asked Questions

Q: Will this fit my Briggs & Stratton 500E series engine?
A: Most B&S 500E series engines (common on newer entry-level mowers) use the 491055 or RC12YC. Check your engine’s model number on the valve cover or blower housing—if it says “500E” and the manual calls for 491055, yes. If it calls for 796560, no.

Q: Do I need to gap this plug before installing?
A: Yes, always check the gap. Most arrive pre-gapped to 0.030”, but shipping can knock it off. Use a feeler gauge to confirm. B&S spec is typically 0.030”, but verify your engine’s manual for exact gap.

Q: Is this the same as a Champion RC12YC?
A: Yes, functionally identical. The 491055 is the OEM Briggs & Stratton number; Champion RC12YC