NGK Spark Plug Stock # 6578

The NGK Spark Plug Stock # 6578 (Model BPR4ES SOLID) is a resistor-type spark plug engineered for reliable ignition across a wide range of small engines and light-duty applications. This 14mm threaded spark plug features a gasket seat design with a 0.749-inch reach, making it a direct fit for engines originally specified with NGK OEM or equivalent ignition components. The resistor core helps suppress electromagnetic interference, maintaining clean ignition performance in demanding conditions.

NGK's proven electrode design and ceramic insulation deliver consistent spark under load, whether in small-engine equipment, compact utility engines, or comparable applications. The gasket seat provides a reliable seal against the cylinder head, eliminating the need for crushing washers and ensuring proper heat transfer away from the electrode. The 0.749-inch reach is critical—too short and the electrode sits recessed; too long and it protrudes into the combustion chamber, both scenarios causing misfires or carbon buildup. This specification ensures the electrode is positioned precisely where combustion chamber geometry demands it.

This spark plug is the correct choice for users who need a direct replacement that matches OEM specifications or who are rebuilding engines and restoring them to factory ignition performance. Technicians and equipment owners value NGK spark plugs for their consistency across service intervals and their compatibility with the vast majority of small-engine platforms. A single spark plug replacement is ideal for routine maintenance or emergency replacement in the field.

The BPR4ES SOLID is part of NGK's standard spark plug line, positioned as a reliable, cost-effective ignition component rather than a premium or high-performance variant. It represents the durable baseline that equipment manufacturers specify when durability and predictability matter more than exotic materials or wide heat ranges.