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

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NGK Iridium IX DCPR7EIX Spark Plugs for 1999-2016 Harley Davidson Twin Cam (Pair)

NGK Iridium IX DCPR7EIX Spark Plugs for 1999-2016 Harley Davidson Twin Cam (Pair)

Product ID: 254497229

Details

Brand
NGK
Core material
Nickel
Thread size
12mm
Top material type
Metal
Vehicle service type
Motorcycle

⚡Up to 3HP power boost

🔧Pre-gapped for perfect fit

🛡️Enhanced anti-corrosion plating

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RD$6052

Duties & taxes included

In stock

Sold byAmazon Dominican RepublicDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

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Description

⚡ Ignite your Harley’s true potential with NGK Iridium IX!

POWER SURGE READY - Unlock up to 3 extra horsepower and feel the difference on every ride.
HARLEY OPTIMIZED FIT - Specifically engineered for 1999-2016 Harley Davidson Twin Cam engines for OEM-level performance.
PRECISION PRE GAPPED - Save time and ensure flawless ignition with factory-set gaps.
NEXT GEN IRIDIUM TECH - Ultra-small 25% smaller iridium electrode means lower voltage needs and longer ignition life.
CORROSION RESISTANT ARMOR - New metal shell plating guards against rust and wear for lasting durability.

NGK Iridium IX DCPR7EIX spark plugs deliver cutting-edge ignition technology with a 25% smaller iridium electrode, pre-gapped precision, and enhanced anti-corrosion plating. Designed specifically for 1999-2016 Harley Davidson Twin Cam engines, these plugs boost horsepower by up to 3HP while extending ignition system life and ensuring smooth, reliable starts.

Specifications

ASIN	B003BUCNNS
Automotive Fit Type	Vehicle Specific Fit
Best Sellers Rank	#38,668 in Automotive ( See Top 100 in Automotive ) #154 in Automotive Performance Spark Plugs
Brand	NGK
Brand Name	NGK
Compatible with Vehicle Type	Motorcycle
Core Material	Nickel
Core material	Nickel
Customer Reviews	4.7 out of 5 stars 4,650 Reviews
Included Components	NGK DCPR7EIX
Item Type Name	SPARK_PLUG
Item Weight	0.09 Pounds
Manufacturer	NGK
Manufacturer Part Number	DCPR7EIX
Model Number	DCPR7EIX
Thread Size	12mm
Thread size	12mm
Top Material Type	Metal
Top material type	Metal
UPC	700155016542
Unit Count	2.0 Count
Vehicle service type	Motorcycle

Reviews

B**6

Working as expected

4.12.2023

M**M

Harley-Davidson

10.04.2025

J**C

Smooth Idle and Stronger Spark – Worth Every Penny

10.02.2026

R**T

Good plugs

10.09.2024

D**L

Funcionales al 100%

Funciona perfecto en una iron 883 del 2020 son el segundo para que compro y sin problemas.

31.03.2026

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