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Home » Top 7 Best Spark Plugs For Harley Davidson (2020 Review)

Top 7 Best Spark Plugs For Harley Davidson (2020 Review)

Owning a Harley Davidson is the dream of every bike enthusiast. And if you’re in for the performance as much as for the looks, then you’re probably aware of the importance of a durable spark plug.
Best Spark Plugs For Harley DavidsonIn the early years, spark plugs used to wear out frequently. So it was a bit of a hassle to replace them now and then. The situation has improved over the years though. Newer and much-improved spark plugs are available on the market these days.

But still, it would be a smart idea to equip your Harley Davidson with the best compatible plug available to ensure longevity and keep servicing at bay.

What is a spark plug and how does it work?

To make it simple, it brings your engine to life. Harley Davidson, like plenty of other vehicles, uses a spark-ignition type engine. Electric current travels through the plug from the ignition system to the combustion chamber.

The plug has a metal shell and a metal core electrode, both isolated by porcelain. As high-pressure current passes through the core, it ionizes the surrounding gas, creating a spark. This spark ignites compressed fuel in the combustion chamber. And boom, your engine’s alive!

Things to know beforehand

The working principles of spark plugs are pretty much the same. However, based on the type of the plug, plug gape, core electrode, ground electrode, insulation, shell, brand, etc, performance and durability may vary significantly. So in this guide, we may be able to help you fish out the best spark plugs for Harley Davidson.

Image
Product
Our Overall
NGK Iridium IX DCPR7EIX Spark Plugs for 1999-2016 Harley Davidson Twin Cam
  • Comes pre-gapped, installation ready
  • Iridium electrode, 25% smaller than conventional Nickel ones
  • Voltage requirement reduced, boosted ignition system life
Amazon's Choice
NGK (4929) DPR8EA-9 Standard Spark Plug For Harley Davidson
  • Laser welded Iridium tip
  • Iridium core, tapered ground electrode
  • Triple gasket seal, longer insulator
Over 370 rating
NGK (5129) DPR7EA-9 Standard Spark Plug For Harley Davidson
  • Solid iridium core
  • Triple gasket seal, longer insulator
  • Dual ground electrodes
Iridium Performance Spark Plugs Pair for Harley Softail Slim Twin Cam Harley# 6R12
  • Ultimate in technology and performance
  • Black and gold finish, anti-corrosive
  • Generates hotter sparks
Accel 2418 Spark Plugs (Pair) 6R12 for Harley Davidson Twin Cam
  • Suitable for all Harley Davidson Twin Cam 1450/1550cc models
  • Larger spark at higher rpm
  • Improved throttle response, reduced fouling
Power sports Spark Plug Each For Harley Davidson
  • Great racing class spark plug
  • Designed with colder heat ranges to handle intense conditions
  • Yttrium alloy core reduces side wire temperature
Harley Road King Performance Spark Plugs Pair OEM# 6R12
  • Conventional copper spark plugs
  • Unique black ceramic body
  • 95% pure Alumina insulator

#1 Spark Plugs For Harley

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

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

One of the best among Harley spark plugs right now. Manufactured by NGK, this Iridium core spark plug is simply amazing. It has a smaller diameter that needs less space than the conventional ones. The iridium core is as much as 25% smaller than even a platinum core, which requires less activation voltage. And less activation voltage means longer life for your ignition system.

This already pre-gapped spark plug features metal shell plating that wards off corrosion even further. Sharp, well-defined tips with high melting points keep it workable for a very long time.

Technical Specifications:

  • Brand: NGK
  • Model: NGK Iridium IX DCPR7EIX
  • Weight: 1.44 ounces
  • Core electrode: Iridium
  • Thread Dia: 18mm
  • Thread Reach: 19mm
  • Pre-Gap Size: 0.8mm
  • Hex Size: 16mm

Pros

Fast and Smooth ignition
Gain up to 3HP with ease
Comes pre-gapped, installation ready
Metal shell plating provides advanced anti-corrosion
25% smaller core electrode. Lower voltage requirement
Better foul protection

Cons

Not the best choice for modified engines
Gap adjustment may be necessary
It can be a bit pricey

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The Best Spark Plugs for Harley Davidson

Item Material Thread NTh
NGK IX DCPR7EIX Iridium 12 19
NGK DPR8EA-9 Iridium 12 19
NGK DPR7EA-9 Nickel 14 19
Iridium Performance Iridium 12 18
Accel 2418 Copper 12 19
Power sports Yttrium 14 19
Pair OEM# 6R12 Copper 12 19
Item Hex Size Gap
NGK Iridium IX DCPR7EIX 16mm 0.8mm
NGK (4929) DPR8EA-9  16mm 0.8mm
NGK (5129) DPR7EA-9 21mm 0.8mm
Iridium Performance 16mm 0.8mm
Accel 2418 Spark Plugs 16mm 1mm
Power sports Spark Plug 16mm 0.9mm
Pair OEM# 6R12 16mm 0.8mm

The top best product [hide]

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


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

Now, we understand you may not always have time to go through a detailed study. You may simply want your spark plug replaced asap. So, without any further ado, check out our list of some of the best Harley Davidson spark plugs.


As mentioned before, it’s the best-rated spark plug for your Harley Davidson. The smaller Iridium core requires less activation voltage. Letting you have an elongated ignition system life. Advanced anti-corrosion shells extend longevity.


Smooth and pop-up free ignition followed by excellent mileage may just be what you’re looking for. It’s possible to gain up to 3HP with ease. Although it’s recommended to consult with an expert first if you’re running a modified engine. The linked package comes as a pair.


While this is a great choice for improving your stock Harley Davidson, this may cause problems on some modified engines. Due to a smaller reach, the spark may not enter enough into the combustion chamber. If you want to enhance the performance further, you may have to go through the alternatives.

Technical Specifications:
Comes pre-gapped, installation ready
Iridium electrode, 25% smaller than conventional Nickel ones
Voltage requirement reduced, boosted ignition system life
Advanced anti-corrosion shells
Fast and smooth ignition, improved hp
Pros
Fast and Smooth ignition
Improved performance and mileage
Gain up to 3HP with ease
Comes pre-gapped, installation ready
Metal shell plating provides advanced anti-corrosion
25% smaller core electrode. Lower voltage requirement
Better foul protection
Cons
Not the best choice for modified engines
Gap adjustment may be necessary
It can be a bit pricey

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NGK (4929) DPR8EA-9 Standard Spark Plug For Harley Davidson


NGK (4929) DPR8EA-9 Standard Spark Plug For Harley Davidson

A good choice to replace your stock Harley spark plugs. Increases bike performance and HP. Fits well on all twin-cam engines. Doesn’t come pre-gapped like the previous one though. Adjustments required. Features a core resistor. Removable terminal post. Corrugated ribs prevent flashovers. High heat resistance.

Technical Specifications:
Laser welded Iridium tip
Iridium core, tapered ground electrode
Triple gasket seal, longer insulator
Increases performance and HP
Pros
Improved throttle response
Trivalent metal coating. Anti-corrosive
Increased performance and HP
Removable terminal post
Corrugated ribs. Flashovers won’t occur
Cons
Gap adjustment necessary
Costlier than conventional ones

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NGK (5129) DPR7EA-9 Standard Spark Plug For Harley Davidson


NGK (5129) DPR7EA-9 Standard Spark Plug For Harley Davidson

Highly affordable if you’re on a tight budget. Comes in a package of 4 pcs. Iridium core electrode with a long insulator. Multiple ground electrodes let you have a backup. Although fuel efficiency may suffer.

Technical Specifications:
Solid iridium core
Triple gasket seal, longer insulator
Dual ground electrodes
Pros
Somewhat cost-effective
Faster ignition
Increased performance
Double ground electrode
Longer lasting
Cons
Need to be careful during adjustments, they are fragile
Not very fuel-efficient

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Iridium Performance Spark Plugs Pair for Harley Softail Slim Twin Cam Harley# 6R12


Iridium Performance Spark Plugs Pair for Harley Softail Slim Twin Cam Harley# 6R12

These unique black and gold-finished Iridium core Harley spark plugs are designed to increase performance and withstand corrosion. The smaller core needs lower voltage to activate. Relatively low fuel consumption than the conventional spark plugs. Results in lower carbon emission. Carbon residue build-up is also a minimum.

Technical Specifications:
Ultimate in technology and performance
Black and gold finish, anti-corrosive
Generates hotter sparks
Available in pairs
Lower activation energy and fuel consumption
Pros
Faster and improved ignition
Better life expectancy
Double ground electrode
Longer lasting
Cons
Need to be careful during adjustments, they are fragile
Not very fuel-efficient

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Accel 2418 Spark Plugs (Pair) 6R12 for Harley Davidson Twin Cam


Accel 2418 Spark Plugs (Pair) 6R12 for Harley Davidson Twin Cam

Accel high-performance spark plugs work great on Harley Davidson Twin Cam models from 1999 and up. It generates a really strong spark that gives higher initial rpm. Ground electrode builds fire inch ball for smoother idle combustion. Consistent ignition Increases performance. The adjustment can be a bit tricky sometimes. Larger gap than conventional ones.

Technical Specifications:
Suitable for all Harley Davidson Twin Cam 1450/1550cc models
Larger spark at higher rpm
Improved throttle response, reduced fouling
Sold in pairs
Pros
Faster and improved ignition
Stronger, much powerful spark
Better throttle response
Resistant to fouling
Better fuel efficiency
Cons
Adjustment problem in some models due to mismatched socket size
Threads do not match in some cases

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Power sports Spark Plug Each For Harley Davidson


Power sports Spark Plug Each For Harley Davidson

This is an Autolite spark plug with Yttrium alloy core inside. Greatly enhances performance even in modified engine Harley Davidsons. If you’re looking for a breakthrough in your vehicle’s performance parameters, this may just be what you’re looking for. Works great under extreme conditions. Three ground electrodes pull out larger sparks for combustion.

Technical Specifications:
Great racing class spark plug
Designed with colder heat ranges to handle intense conditions
Yttrium alloy core reduces side wire temperature
Thread Diameter- 12mm. Thread Reach- 0.75 inches. Hex Size- 5/8 inch
Diamond fire electrode technology creates quality sparks
Reduced emission, longer plug life
Three ground electrodes
Pros
Engine performance increases significantly
Works great on modified engines
Improved fuel consumption, reduced emissions
Better flame propagation
Cost-effective
Cons
Impacts low-end power in some cases
Fitting problems may occur
Higher voltage may lead to thermal crackings

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Harley Road King Performance Spark Plugs Pair OEM# 6R12


Harley Road King Performance Spark Plugs Pair OEM# 6R12

Conventional copper core spark plug. Works great on Harley Road King Twin cam 2000-2020 only. Great heat shock resistance, excellent insulation.

Technical Specifications:
Conventional copper spark plugs
Unique black ceramic body
95% pure Alumina insulator
Sold in pairs
Suitable for Harley Road King Twin Cam 2000-2020
Pros
Conventional plugs work just fine
Good budget buy
Fits well on Harley Road King Twin cam 2000 and above models
Cons
Poor durability. Compatibility issues are glaringly present
Model specific.May cause a drop in performance in other models
Vulnerable to high heat ranges
Increased emission compared to similar products available in the market

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Popular brands that produce Harley Spark Plugs

Harley spark plugs vary from model to model, brand to brand. It’s a growing, competitive market out there. The build, quality, material, performance, everything changes with the name of the brand as they all want to leave their innovative signature touch in their products. Some of the companies have been in this business for centuries. Here is a list of some of the top brands that produce Harley spark plugs.

NGK Spark Plugs

NGK Spark Plugs
One of the leading OEM producers in the world. They have over 80 years of experience in this market and they always put performance and quality above all others. They offer a lot of models to choose from for your Harley Davidson. By installing their merchandise, most have seen an instant improvement in their bike’s ignition and transmission. For more information and compatibility checks, click here.

Autolite Spark Plugs

Autolite Spark Plugs
The Autolite company started in 1911 by selling buggy lamps. By the year 1936, they produced their first spark plug. Since then they have been developing by leaps and bounds. Presently they have a wide variety of automobile products. The spark plugs they produce for Harley Davidson are some of the bests in the market. Click here for more information.

Pulstar Spark Plugs

Pulstar Spark Plugs
Pulstar is an innovative brand. They use unconventional plasma-assisted combustion technology that boosts your Harley’s horsepower. Moreover, an improved torque and throttle response have been recorded. Pulstar ensures quicker response, efficient fuel consumption, and reduced carbon emission. Check out more from here.

Denso Spark Plugs

Denso Spark Plugs
A popular Japanese brand. Denso started as part of the Toyota brand but later emerged as a self-dependent company. They produce quality spark plugs Harley Davidson as well as other essential components for the vehicle industry. Get to know them better at here.

E3 Spark Plugs

E3 Spark Plugs
The E3 spark plugs feature DiamondFire spark plug technology. They promise increased vehicle performance, efficient fuel consumption, and lower carbon emission. Multiple ground electrodes generate larger bursts of sparks. These plugs are excellent for racing gears as they prioritize better burn for the engine. Their premium performance OEM replacement plugs can certainly fire up your engine like never before. Wanna know more? Just click here.

Spark plugs for different Harley Davidson models

Compatibility is one of the major issues to look out for when replacing your spark plug. Depending on your Harley model, it can be tricky sometimes. There are hundreds of brands out there that make spark plugs for Harley Davidson. They produce model-specific products. So the same plug that works great on a model may not turn out to be the best option for another one.

Some of the leading brands like NGK, Autolite, E3, Pulstar, Denso, Champion, Accel, Brisk, etc produce universally compatible quality plugs. We’ve prepared a list of Harley models and the type of OEM components they work best with to give you a better chance of filtering.

Spark plugs for Harley Davidson 2015 FLHTK

NGK- DCPR7EIX, Autolite-XS4164, Accel U-Groove 2418, Champion-RA8HC, Pulstar Plasma-HE1HT9, Accel Platinum-Y2418P.

Spark plugs for Harley Davidson 1200

NGK- DCPR7EIX, Autolite-XS4164, Accel U-Groove 2418, Pulstar Plasma-HE1HT9, E3.36.

Spark plugs for Harley Davidson Sportster 883

NGK- DCPR7EIX, Harley Davidson Stock OEM-6R12, E3.36, Denso-IXU22, Champion-RA8HC, Bosch-0242135515.

Spark plugs for Harley Davidson Road King

NGK- DCPR7EIX, Autolite-XS4164, E3.36, NGK-DCPR7E, Accel Platinum-Y2410P, Champion – RN12YC, Champion-RA8HC, Pulstar Plasma-HE1HT9.

Spark plugs for Harley Davidson 103

NGK- DCPR7EIX, Brisk-6R12, E3.36, Champion-RA8HC, Brisk-BR14YS-9.

Spark plugs for Harley Davidson Twin Cam

NGK-6046, NGK-DCPR7EIX, Harley Davidson OEM-6R12, E3.36, Denso-IXU22, Champion-RA8HC, Bosch-0242135515.

Spark plugs for Harley Davidson Evo

NGK-BPR5EIX-11, Harley Davidson OEM-5R6A, E3.34, Denso-IW16, Champion-RN12YC, Bosch-0242229779.

As you may have noticed, some of the spark plug versions go well with almost any Harley Davidson model. So even if your Harley is not listed above, there’s a chance that these plugs will work on yours too. Although, it’s always better to double-check. Consult with an expert about your specific model. Highly advised if you have a modified engine.

Our Overall
Fast and Smooth ignition
Improved performance and mileage
Gain up to 3HP with ease
Comes pre-gapped, installation ready
Metal shell plating provides advanced anti-corrosion
25% smaller core electrode. Lower voltage requirement
Better foul protection

Spark plug for Harley Davidson – Buying guide

best spark plugs for harley davidsonWe’ve already pointed the top-rated plug out there for you Harley Davidson. But before you run off to the store, here are some things to know that may help you make the best out of this purchase.

Brand Selection

Starting with the right brand simply narrows down your search. There are hundreds of brands that produce spark plugs for Harley Davidson Some of them are well known for producing high-quality, sturdy products. So buying a brand product means you may find plenty of available information, reviews on the product. Here are some of the most popular brands in this industry that produce spark plugs for Harley Davidson.

    • NGK Spark Plugs for Harley Davidson

One of the most widely recognized OEM brands. This Japanese company has been producing top-quality, innovative parts since the 1930s. Their iridium core spark plugs are one of the best plugs available on the market at the moment.

    • Pulstar Spark Plugs for Harley Davidson

These unconventional plugs use innovative plasma-assisted combustion technology. Extensively tested in the USA, they claim to generate more horsepower, improved throttle response, and better torque.

    • Autolite Spark Plugs for Harley Davidson

Has been producing high-quality spark plugs for various kinds of combustion engines since 1936. They mainly focus on performance-driven quality for the vehicles. Worthy of consideration.

    • Splitfire Spark Plugs for Harley Davidson

Used to be a popular brand, heavily advertised in the early 1990s. But their product distribution has downgraded over the years. Their official website is not functional anymore.

Plug Type

After the general classification based on brands, you might want to know what type of plug you are looking for. This field also diversifies into several subcategories such as plug materials, ground type, gap type, reach, etc. It may be worth looking into if you want to have a transparent idea about your purchase.

Metallurgy

In the early years, electrodes used to feature Copper cores. Well, solid Copper with Nickel alloy coatings to be precise. They used to work great with the ignition systems in 1980 or before. But in modern times, they are not as popular as they used to be. The main reason being they build up deposits pretty quickly and start to develop knocks or pop-ups. Not quite the desired feature.

Platinum cores, however, resolve this problem by reducing the amount of deposit built up. These cores ensure much better performance and longer lifetime for your spark plug.

Although nowadays, new alloys such as Iridium and Yttrium have been showing promising improvement in the performance of spark plugs. Iridium plugs produce a slightly less powerful spark than the Yttrium ones.

But they convey heat much better that leads to a longer lifetime. Yttrium plugs may undergo quicker thermal/electrical corrosion, but they can generate hotter sparks to fire up your Harley real fast. So longer lifetime or performance, it’s your call.

Ground Type

Electrodes come in single or multiple ground variants. Multiple ground variants last longer while single ground variants are fuel-efficient.

Gap Type

Some electrodes are pre-gapped. Depending on the brand the gap may be adjustable or fixed. So it may be a good idea to consider the existing gap of your stock plug before switching to an OEM one.

Plug Reach

The reach of a plug is a fairly important feature. You would want your plug to protrude into the combustion chamber just enough to ignite the engine smoothly. Too deep into the combustion chamber may cause pre-ignition and end up damaging the plug itself. So once again, you may want to relate to your stock plug.

Thermal Range

Spark plugs differ from each other based on their heat conveyance. Lower numbers mean they heat up real fast. While a higher number indicates high specific heat, cooler plug. If you’re not sure which one to choose, you could always consult with an expert.

Quality and Functionality

Watch out for the quality of your purchase. You’re looking to enhance the performance of your Harley. Wouldn’t want all this to somehow backfire now, would you? Go for the options that have detailed information on their features. This way, you’ll have an easier time making your selection.

Compatibility

All these studying will be for naught if your Harley and the plug aren’t compatible with each other. Things to consider here are the model of your Harley, engine model, fuel system, part number, stock plug model, etc. Some web forums also provide info on spark plugs for Harley Davidson that leaks oil. Going through product/blog reviews may be a good idea to minimize compatibility issues.

Important

For more information, look no further. At the official Harley Davidson service web portal, you may find all you need to know about your bike and how to install/replace spark plugs with ease. Make sure to submit your vehicle identification number (VIN) and you should be good to go.

Why you should change spark plugs you will know from this video:

Spark plugs for Harley Davidson FAQs

What is Gapping?

Gapping is the opening between the tip of the central electrode and the ground electrode. It determines the quality of the spark your plug will generate. Each Harley has a specific gapping range. Make sure your OEM plug fits into the range.

What does the metal do in a spark plug?

The metal forms up the core and the ground electrode. It’s used to channel high voltage electricity to ionize the gas in the gap and generate a spark. Depending on the company, the metal may be different. The performance may also vary with the material.

How often should I change the plug?

It depends on the brand and the intensity of usage. Excessive use and long drives without breaks often lead to thermal crackings. High-performance plugs tend to wear out much faster. If you want to be on the safe side, regular servicing may be the key.

Longer or shorter reach?

The reach indicates how much the plug protrudes into the combustion chamber. A longer reach enters well into the chambers but may be damaged by the pistons. Shorter reach may not be able to ignite the fuel properly. Depends on your model.

What are “Hot” and “Cold” plugs?

They represent thermal ranges in which a type of plug is most efficient. Hot plugs have long insulation nose, slower heat deposition rate. Good for low rpm engines. The cold plugs are vice-versa. Generates high rpm.

Which thermal range to select?

It depends on your engine and ignition system. It should be well defined in your user manual. If your selected thermal range is too low, you may encounter difficulties firing up the engine. Also, there may be a risk of fouling. But if it's too high, you are risking detonation, pre-ignition, and power loss.

Verdict

Since there are plenty of options out there, equipping your Harley Davidson with the best compatible spark plug can be tricky. A well compatible plug can improve your engine power and speed, grant swift transmission, reduce corrosion, and carbon emission. On the other hand, a bad (not compatible) one is bound to give you a bitter experience.

For the best results, choose between a modern Iridium and Yttrium core-based plug considering your model. Keep the thermal range, gap size, etc in mind before finalizing your purchase. For pre-gapped plugs, check the gap range.

Consult with an expert first if you have a modified engine or in any case you’re not certain. Remember, you could always visit Harley Davidson’s official service panel for any further support. Happy Rolling!