Moroso 28331 Ultra 40 Spark Plug Wire Set for Harley-Davidson Sportster

The Moroso Ultra 40 Spark Plug Wire Set (PN 28331) is purpose-built for Harley-Davidson Sportster applications, delivering race-proven ignition performance to your motorcycle. Trusted at the highest levels of motorsport — from dual-mag Top Fuel dragsters to NASCAR Cup Series competitors — Moroso Ultra 40 wires set the benchmark for high-performance ignition wire technology.

At the core of the Ultra 40 design is an 8.65mm diameter wire featuring a precision spiral-wound conductor engineered to maximize energy transfer from coil to plug. The tightly wound spiral geometry delivers a consistent, powerful spark while maintaining just 40 ohms of resistance per foot — a balanced specification that suppresses electromagnetic and radio frequency interference (EMI/RFI) without sacrificing spark energy.

Key Features:

• 8.65mm diameter high-performance ignition wire
• 40 ohms/foot spiral-wound conductor for optimized energy transfer
• Superior EMI and RFI suppression for clean ignition signal
• Race-proven technology used in Top Fuel and NASCAR applications
• Direct-fit design for Harley-Davidson Sportster models
• Durable outer jacket engineered to withstand high-heat engine environments

Whether you're building a track-day machine or simply want the most reliable ignition wire available for your Sportster, the Moroso 28331 Ultra 40 wire set is a direct-fit, no-compromise upgrade over stock ignition wires.