NGK Spark Plug Stock # 4551

The NGK Spark Plug Stock #4551 (BR9HS-10) is a resistor-equipped spark plug designed for reliable ignition in small-displacement and mid-range engines, commonly found in motorcycles, ATVs, lawn equipment, and light automotive applications. This plug is ideal for riders and mechanics who prioritize consistent cold-start performance and fuel efficiency.

The BR9HS-10 features a resistor-type design that suppresses electromagnetic interference, protecting engine control modules and radio systems from spark-induced noise. With a 10mm thread diameter and a heat range of 9, this plug ensures optimal heat dissipation in moderately tuned engines, preventing fouling under rich conditions while resisting pre-ignition in lean-running setups. NGK's copper-core electrode design promotes rapid ionization and faster flame kernel development, enhancing throttle response and combustion efficiency.

This spark plug is particularly beneficial for owners maintaining OEM-specification ignition systems on single-cylinder engines, small cruisers, pit bikes, and compact utility equipment. Installation is straightforward with a standard 13/16-inch hex socket and requires no gap adjustment, as NGK pre-sets the gap to factory specifications. Whether performing seasonal maintenance or rebuilding after a long storage period, the BR9HS-10 delivers the dependable spark needed for optimal engine performance.