NGK spark plug R6252K-105

The NGK spark plug R6252K-105 is a racing spark plug for high-output two-stroke applications, commonly specified for IAME X30 kart engines and many Kawasaki KX85/KX100/KX112 models. It uses a resistor design and fine-wire, non‑projected center electrode to provide reliable ignition under extreme temperature and vibration.

Technical specifications

• NGK part number: 2741 (R6252K-105 Racing Series)
• Thread size: M14 x 1.25, reach 19 mm (3/4"), flat/gasket seat
• Hex size: 13/16" (21 mm) wrench diameter
• Resistor: Yes, 5 kΩ internal resistor (solid, non‑removable terminal nut)
• Heat range: 10.5 (NGK racing scale)
• Center electrode: Copper core with nickel fine‑wire tip, non‑projected
• Ground electrode: Single slant ground, nickel core with platinum pin tip
• Pre‑set gap: 0.031–0.032 in (0.8 mm), crush washer included
• Insulator: Alumina silicate ceramic with corrugated ribs, height 2.2 in

Service context

This NGK R6252K-105 plug targets racing use only, with a wide heat range to manage high combustion temperatures and reduce fouling in competition conditions. NGK lists a typical longevity of up to 30,000 miles in suitable applications, but in karting and motocross it is usually treated as a regular service item and replaced based on tuning practice, plug color, and performance.

Installation

The NGK spark plug R6252K-105 installs as a direct replacement where specified, using a 13/16" plug socket and standard crush-washer torque (NGK reference: 18–25.3 lb·ft in cast iron, 18–21.6 lb·ft in aluminium heads).

What's included

Each box contains one NGK R6252K-105 racing spark plug (part no. 2741) with crush washer.