Briggs & Stratton Plug-spark Part # 491055T

What It Is

The Briggs & Stratton Spark Plug Part # 491055T is an OEM replacement spark plug designed for small engines—primarily lawn mowers, tractors, and other outdoor power equipment. It delivers the spark needed to ignite the fuel-air mixture, ensuring reliable starts and smooth engine operation.

Fitment & Compatibility

Before buying, confirm your engine’s model and type numbers (found on the engine shroud or near the spark plug hole). This plug fits most Briggs & Stratton engines with a 14mm thread diameter and a 3/4-inch reach. Common compatible engines include the 500E, 550E, 625E, 675EX, 725EX, and many Intek, Vanguard, and Endurance series. Measure your old plug’s thread length and diameter to verify—using the wrong reach can damage the piston or threads. This is an OEM part, so it matches original specs for Briggs engines; aftermarket equivalents (e.g., Champion RC12YC) exist but may vary slightly in heat range or gap. Check your equipment’s manual or Briggs’ online lookup tool for exact fitment.

Key Things to Buy

• Quality: OEM part ensures correct heat range and electrode material, reducing misfire risk. Aftermarket plugs may work but can degrade faster.
• Installation difficulty: Simple for DIYers—remove the old plug with a 13/16-inch or 5/8-inch socket, gap to 0.030 inches (check manual), and torque to 20-25 ft-lbs. Over-tightening can crack the ceramic.
• Common gotchas: The plug is pre-gapped but always verify with a feeler gauge—shipping can shift it. Use a thin layer of anti-seize on threads to prevent seizing in aluminum heads, but avoid getting it on the electrode.
• Life expectancy: Replace annually or every 100 hours of use for optimal performance. Fouls faster in dirty or oil-burning engines.

Should You Buy It

Yes, if you own a Briggs & Stratton engine mower or small tractor and want a drop-in, reliable spark plug that matches factory specs. It’s a low-cost, high-value part for routine maintenance—especially if your engine is hard-starting, misfiring, or due for a tune-up. Skip it only if you need a different thread size (e.g., 18mm) or a non-Briggs engine.