NGK Spark Plug - #6637/04 — Indian Motorcycle Chief, Scout, Spirit (1999-2003)

NGK spark plug #6637/04 is a genuine replacement for V-twin motorcycles, including Harley-Davidson and Indian models. Built to OEM ignition specifications for reliable cold starts and consistent combustion across the RPM range.

Features

• Genuine NGK manufacturing
• V-twin motorcycle fitment
• Cross-compatible with ILKR8Q7 and BPR8ES variants

Specifications

• Brand: NGK
• Manufacturer Part #: 6637
• UPC: 087295166376
• Length: 3.2 in
• Width: 1 in
• Height: 0.7 in
• Weight: 0.1 lbs
• Country of Origin: Japan

Fitment

Fits V-twin motorcycles, including Harley-Davidson and Indian Motorcycle models.

Frequently Asked Questions

What motorcycles does this plug fit?

NGK #6637/04 fits most V-twin motorcycle engines, including Harley-Davidson and Indian models. Verify your owner's manual before ordering.

Can I use ILKR8Q7 or BPR8ES instead?

Yes — ILKR8Q7 can substitute for ILKR8Q, and BPR8ES can substitute for BPR8ES-S. Cross-reference your original part number first.

How often should I replace this spark plug?

Follow your motorcycle's service schedule, typically every 10,000–20,000 miles depending on riding conditions and engine design.

Is this an OEM part?

This is a genuine NGK replacement plug built to OEM ignition specifications, not an aftermarket copy.