NGK 7791 Spark Plug

Racing Spark Plug Overview

NGK 7791 is a racing spark plug built with a copper core center electrode, nickel tip materials, and a 5,000 ohm resistor for stable ignition performance. It uses a flat seat, 10 mm thread diameter, 5/8 hex, and a .75 reach for the specified application.

Fits 2005-2009 Honda CRF250R, N/A. This NGK spark plug is identified by part number 7791 and stock number 7791, with a pre-gap of .028 and a pin-type ground electrode design.

Key Features

• Copper core center electrode for efficient spark transfer.
• Nickel center and ground electrode tip materials.
• 5,000 ohm resistance for ignition system control.
• Flat seat, 10 mm thread, and 5/8 hex for the listed fitment.
• Pin-type ground electrode with slant configuration.

Detailed Description

NGK 7791 is a secondary ignition spark plug engineered around OE-style construction and consistent electrical performance. The copper core center electrode, nickel tip materials, and 5,000 ohm resistor work together to support reliable spark delivery, while the .028 pre-gap and heat range 8 specification match the listed application requirements. The part number 7791 is also referenced as R0409B-8.

For buyers searching for a Honda CRF250R spark plug or an NGK 7791 replacement, this plug provides the specified thread diameter, reach, seat type, and terminal style needed for the application. It is a direct match for the listed 2005-2009 Honda CRF250R fitment.

What It Is Used For

• Replacing a worn or fouled spark plug.
• Restoring consistent ignition performance.
• Addressing hard starting caused by plug wear.
• Correcting misfire concerns related to spark degradation.
• Maintaining the specified gap and heat range for the application.

Installation Notes and Tips

Verify the thread diameter, reach, seat type, and terminal style before installation. Set the gap to the specified .028 inch pre-gap if required by the application, and confirm the ignition system is in good condition before final assembly. Use the listed fitment only: 2005-2009 Honda CRF250R, N/A.

Quality Assurance

NGK is a major OE spark plug supplier in North America with more than 80 years of automotive experience. The brand manufactures ignition components to original equipment standards and supports a wide range of automotive, motorcycle, marine, and small engine applications. Part number 7791 reflects that OE-focused manufacturing approach.