RC12YC Spark Plug for BS 491055 491055S 692051 792015 5066 Kohler 25 132 12-S M78543（Pack of 4）

What It Is

This is a pack of four RC12YC spark plugs, a standard replacement for small engines in lawn mowers, tractors, and other outdoor power equipment. They ignite the fuel-air mixture in the combustion chamber, ensuring reliable starting and smooth operation.

Fitment & Compatibility

Before buying, confirm your engine model. These plugs directly replace Briggs & Stratton part numbers 491055, 491055S, 692051, 792015, 5066, and Kohler 25 132 12-S and M78543. They fit most engines with a 14mm thread diameter and a 3/4" reach, but always check your current plug’s thread size and gap (factory set to 0.030"). Not for engines requiring a resistor or extended-tip plug unless cross-referenced. Verify your mower’s brand and model—common on Toro, John Deere, Craftsman, and Husqvarna with compatible engines.

Key Things to Know

• Quality: Copper-core design offers good conductivity and durability for standard use, but not as long-lasting as iridium or platinum plugs.
• Installation: Easy—remove the old plug, gap the new one (0.030"), and torque to 20 ft-lbs. Over-tightening can strip threads.
• Gotchas: Check for cross-threaded installation; use a spark plug wrench. These are pre-gapped, but always verify with a feeler gauge. Not for high-performance or racing engines.
• Pack of 4: Useful for multi-cylinder engines or as a spare set, but most push mowers need only one—store extras in a dry place.

Should You Buy It

A solid choice for routine replacement on common Briggs & Stratton and Kohler engines in residential mowers or tractors. The price is low, the rating is strong, and the fitment is broad—just confirm your engine’s plug specs before ordering. Ideal for DIY maintenance, not for professional heavy-use or high-compression engines.