RC12YC Spark Plug for RC12YC Compatible with Briggs & Stratton 491055 491055S 491055T 72347GS 72347 805015 M78543 for Kohler 12 132 02, 12 132 02-S, 25 132 12-S (Pack of 10)

What It Is

This is a pack of 10 RC12YC spark plugs, a standard replacement part for small engines in lawn mowers, tractors, generators, and pressure washers. It’s designed for 4-stroke engines requiring a 14mm thread, 0.708” reach, and 0.030” gap.

Fitment & Compatibility

Before buying, confirm your engine model. This plug directly fits Briggs & Stratton engines requiring part numbers 491055, 491055S, 491055T, 72347GS, 72347, 805015, or M78543, and Kohler engines using 12 132 02, 12 132 02-S, or 25 132 12-S. Measure your old plug: thread diameter must be 14mm, thread reach 0.708” (18mm), and hex size 13/16” (21mm). Cross-reference with OEM specs—this is a copper-core, non-resistor plug, so avoid it if your engine requires a resistor plug (often labeled “R” in the part number). Verify your mower’s deck size or model number doesn’t matter; only the engine’s spark plug spec counts.

Key Things to Know

• Quality: These are standard copper-core plugs, not iridium or platinum. They work fine for normal use but need replacement more often (every 100 hours or seasonally).
• Installation: Easy—remove old plug, gap new one to 0.030” using a feeler gauge, hand-tighten, then torque to 20-25 ft-lbs. Over-tightening can crack the porcelain.
• Common gotcha: The pack of 10 is overkill for a single mower. Share with a neighbor or stock up for multiple engines. Check your engine’s gap spec; some Kohler models require 0.025” instead.
• Compatibility trap: Not all RC12YC plugs are identical—cheap knockoffs may have loose tolerances. This set is branded RC12YC but verify the thread reach matches your engine’s depth.

Should You Buy It

If you own multiple small engines (mower, pressure washer, generator) that all use RC12YC plugs, this pack saves money per plug. For a single mower, a 1-pack is cheaper unless you want spares. Avoid if your engine requires a resistor or platinum plug.