Should I gap to my owners manual spec or are they designed to work with the smaller pre-gap they came with?

Harley Davidson recommends 0.40" gap. As to "You should never gap an iridium plug", NGK's website states for Harley Davidson, these should be gapped at 0.40". I've found many websites stating that if re-gap is needed use care not to damage the electrode or the porcelain center. So, it's not that you should not re-gap, it's that you should be extremely careful.

Is this 6r12, if so why does it not say so ?

Because these plugs are IX DCPR7EIX 99 TO 16 HARLEY-DAVIDSON

Ngk Iridium Ix Dcpr7eix Spark Plugs For 1999 2016 Harley

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Description

⚡ Ignite your ride with NGK Iridium IX – where power meets precision!

IRIDIUM EDGE TECH - 25% smaller iridium electrode slashes voltage needs and extends ignition life.
POWER SURGE READY - Unlock up to 3 extra horsepower instantly for your Harley Twin Cam.
PRECISION PRE GAPPED - Arrives perfectly pre-gapped for hassle-free installation and peak ignition.
TAILORED FIT FOR HARLEY - Specifically engineered for 1999-2016 Harley Davidson Twin Cam models.
CORROSION RESISTANT ARMOR - New metal shell plating guards against rust and wear for long-lasting reliability.

NGK Iridium IX DCPR7EIX spark plugs deliver cutting-edge ignition performance with a 25% smaller iridium electrode that reduces voltage requirements and extends system life. Pre-gapped for easy installation, these plugs provide up to 3 horsepower gain and feature advanced anti-corrosion plating, making them the perfect upgrade for 1999-2016 Harley Davidson Twin Cam motorcycles.

Specifications

ASIN	B003BUCNNS
Automotive Fit Type	Vehicle Specific Fit
Best Sellers Rank	#117,673 in Car & Motorbike ( See Top 100 in Car & Motorbike ) #579 in Ignitions
Brand	NGK
Brand Name	NGK
Compatible with Vehicle Type	Motorcycle
Core Material	Iridium
Customer Reviews	4.7 out of 5 stars 4,883 Reviews
Item Type Name	SPARK_PLUG
Item Weight	0.09 Pounds
Manufacturer	NGK
Manufacturer Part Number	DCPR7EIX
Model	DCPR7EIX
Number of Items	2
Thread Size	12mm
Top Material Type	Metal
UPC	700155016542
Unit Count	2.0 Count
Vehicle Service Type	Motorcycle
What Is In the Box	NGK DCPR7EIX

Reviews

B**6

Working as expected

OEM fit for Harley Davidson Fatboy 103 Ci twin cam engine. Smooth starting and running.

4.12.2023

R**.

Good spark plugs for my Harley Fat Bob

Using these for the past many years, good replacement for OEM spark plugs

6.11.2023

A**T

Excellent trustworthy performance

NGK Iridium IX spark plugs are a great upgrade for anyone looking for reliable performance and long-lasting quality. They provide smooth starts, consistent ignition, and dependable performance. Installation was straightforward, and the build quality feels excellent. Overall, these plugs are a solid choice for improving reliability and getting consistent performance from your engine. Definitely a product I would recommend!

27.08.2026

M**M

Harley-Davidson

Good update for my Harley

10.04.2025

P**D

Satisfait

Parfait pour ma moto

18.10.2026

D**.

Originales

Original.

2.09.2026

R**T

Good plugs

Just as good as the Harley ones. I feel no difference. Running these plugs now for 20k km.

10.09.2024

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