5 Best Spark Plugs for Harley Davidson – Reviews 2023

When considering best spark plugs for Harley Davidson motorcycles our experts created a list of features that would make one spark plug a better choice than other spark plugs. Their list included the materials the spark plug is made from, especially the core.

We also considered the sharpest points on the plugs, you want these points to remain sharp as long as possible, so you want plugs made from materials that are hard and have high melting temperatures.

Lastly, they considered the size of the center of the electrode. The smaller centers require less voltage to spark.

Our Top Picks In 2023





1. Nickel plated terminal.

2. Reduces carbon emissions.

3. Increases power.

1. Requires less voltage.

2. Iridium electrode.

3. Cost a little more.

1. Anti-corrosion coating.

2. Iridium electrode.

3. Increases fuel efficiency.

1. Increases engine power.

2. Pre-gapped.

3. Increases Horse Power.

1. Improve throttle response.

2. High durability to heat.

3. Longer insulator.

Best Spark Plugs for Harley Davidson Reviews 2023

1. E3 Spark Plug E3.36 Powersports Spark Plug

These spark plugs are designed to improve your bikes performance, increase your speed, and reduce the harmful emissions your bike produces. They are typically preferred by racers, and people who have the need for speed.

These plugs are not run of the mill plugs. They are specifically designed for the engines they are recommended to fit. This tailored design allows the plug to have an optimized spark gap according to your engine size, and performance needs.

The design of the ground electrode allows the plug to be projected further into the combustion chamber so it sits closer to the air and fuel mixture. That allows the fuel to be sparked quicker, and burned more efficiently.

These plugs have a thread diameter of 12mm, a thread reach of 0.75 inches, and they have a Hex size of 5/8”.


  • Increases power.
  • Makes engine run smoother.
  • Improves fuel consumption.
  • Reduces emissions.


  • Costs a little more than standard plugs.
  • Specifically sized so may not fit all motorcycles.


  • Nickel plated terminal end.
  • Contains an alloy enhanced by Ytrium that can reduce side wire temperature by 8%
  • No need to gap the E3’s; they are ready to plug in and use.
  • The design of the E3 is open at the end to allow for more complete.
  • combustion. This design is called “Diamond Fire” and it allows the fuel to be used more efficiently.
  • Reduces carbon emissions and carbon build-up

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

This pair of spark plugs is designed to fit a large number of Harley Davidson motorcycles produced from 1999 until 2016. The plugs are designed with technology that provides you with an additional 3HP.

The center electrode is made from iridium. The iridium electrode is as much as 25% smaller than electrodes made from other materials like nickel and platinum. 

This smaller electrode allows the plug to spark with much lower voltage amounts. This means your bike starts faster and lasts longer because of less wear and tear. These plugs come pre-gapped. They are ready to plug in place and go to work.


  • Iridium electrodes are as much as 25% smaller than traditional platinum or nickel electrodes.
  • Lengthens ignition system life expectancy.
  • Requires less voltage.
  • Comes in a package of 2.


  • May not fit all motorcycles.
  • Cost a little more than traditional plugs.


  • Pre-gapped.
  • Iridium electrode.
  • Metal shell with anti-corrosion properties.
  • Can give you a gain of as much as 3HP.
  • Smaller center electrode diameter.

3. Tuning Store Harley-Davidson Iridium Performance Spark Plugs Pair

These spark plugs come in pairs. The plugs are designed with iridium electrodes to increase performance and extend the life of the plugs, and your bike.

Iridium electrodes can be made smaller than nickel or platinum electrodes due to the abilities of the metal. This means that you have to have less voltage available to create a spark with the plug.

Less fuel is required in the combustion process, and the fuel that is used is used more efficiently so the bike has cleaner emissions, and less carbon residue building up in the engine.

The plugs are so versatile that they will fit any twin cam Harley Davidson designed between 1999 and 2017. That makes getting the right plug easier.


  • Iridium electrodes are smaller than standard nickel or platinum electrodes.
  • Hotter spark.
  • Extended life expectancy.
  • Exceeds the OEM requirements and expectations.


  • Cost slightly more than standard plugs.
  • The gap may need to be re-set when installed.


  • Iridium electrodes.
  • Protective anti-corrosion coating.
  • Fits all 1999 – 2017 Twin Cam Harley Davidson motorcycles.
  • Improves bike performance.
  • Increases fuel efficiency.

4. NGK # 6046 Iridium Spark Plugs -- DCPR7EIX -- for Harley-Davidson Twin Cam and XL

NGK has been known to produce high quality spark plugs for a long time, and these iridium plugs are some of the finest ones they have developed to date.

The Iridium plugs are higher in quality than plugs that have electrodes made of nickel or platinum.

Iridium allows the diameter of the electrode to be smaller, which in turn allows the spark plug to be powered with less voltage.

These plugs come in a four pack, and they are extremely long lasting. They perform better, and provide a quicker engine start than the majority of standard plugs. 

They will fit a wide range of Harley Davidson bikes, but you are cautioned to check the specifics and make sure they fit your bike before you order. The plugs are pre-gapped, but some bike owners do adjust the gap because of their own preferences.


  • Increases engine power.
  • Makes the bike start faster.
  • Lasts longer than standard plugs.


  • You must be careful when setting the gap these plugs can be fragile.
  • Cost a little more than standard plugs.


  • Pre-gapped.
  • Iridium.
  • Comes in a 4 pack.
  • Fit a large number of Harley Davidson bikes.
  • Have the ability to increase horse power of bike.

5. NGK (6046) DCPR7EIX Iridium IX Spark Plug

These spark plugs are designed to increase performance on any bike they are installed in. They have a 0.6mm laser welded tip made of iridium that makes them more durable than standard plugs.

That means you will get more use from the plugs, and more miles before you have to change them.

The consistent and stable spark they produce will help to reduce the electrical quenching that can occur.

They have corrugated ribs located on the insulator that helps to stop flashover from happening, and they have a triple gasket seal that stops combustion gas leakage from occurring.

They are perfect for the high performance engines that are being built today because iridium has a very high melting point and can withstand the heat and the pressure produced by those engines. They are simply an excellent choice for the majority of Harley owners.


  • Improved throttle response.
  • Has trivalent metal plating which contains anti-corrosive and anti-seizing properties.
  • Has a high durability to heat.
  • Corrugated ribs that prevent flashovers from occurring.


  • Costs a little more than standard plugs.
  • Only 1 plug in each pack.


  • Iridium electrodes.
  • Laser welded iridium tip.
  • Tapered ground electrode.
  • Longer insulator.
  • Triple gasket seal.

How to pick the best spark plugs for Harley Davidson

When you are ready to replace the spark plugs on your Harley Davidson then you want to get plugs that will be best for the bike you ride. To choose the best plugs for your particular bike consider the following things before buying.

The Materials the plugs are designed with

You want to buy plugs that have a high conductivity so your bike starts faster and easier. Copper has been the best choice in spark plugs for many years, but iridium has quickly become the shining star.

Iridium allows the center electrode diameter to be smaller than average. By reducing the size of the electrode center you also reduce the amount of voltage that is required to allow the plug to create a spark.

The reduced voltage requirement increases the longevity of the plug, and the engine of your bike.

You also need to consider that iridium is supposed to be up to 6 times harder than the platinum that is commonly used in most standard spark plugs. The stronger material will allow sharp points on the plugs to stay sharper for longer periods of time, so the plugs will perform better, and last much longer.

Pre-Set Gaps

If the spark plugs that you purchase already have a gap setting that is perfect for your bike then you will save time, effort, and possible complications. Setting the spark plug gap on a traditional spark plug can be done with a simple screwdriver prying the center and widening the gap between the two electrodes.

Newer spark plug designed that incorporate harder materials like iridium are not as easy to pry apart, and sometimes they are more fragile and easier to break. Try to find plugs that are already gapped and are ready to plug in and put to work.

Read the Owner’s Manual

Your owner’s manual to your bike will recommend specific spark plugs for the best engine performance. If your owner’s manual suggests that you use iridium plugs then never consider downgrading and using standard platinum plugs.

If you use a spark plug that is of lesser quality then there is a good chance that you will cause some engine damage. You can use a higher grade spark plug, but never a lower grade.

Ask an Expert

If you are uncertain what plug to buy for your bike it is wise to ask an expert mechanic what they suggest. The spark plug is a major engine component that can make a big difference in performance and life expectancy for the engine.

Final Note

Spark plug replacement is an important bike maintenance issue. The right spark plug can increase performance, increase speed, increase engine power, reduce corrosion, and reduce emissions. The wrong spark plug can give you a daily headache each time you go to start your bike.

Do not be hasty when buying your new spark plugs. Research the plugs, and determine what you need most from your plugs. Then choose a plug made of high quality materials, and designed to fit your bike. Pre-gapped plugs provide you with optimum starting ability and fewer headaches.

Alston Seymour

A Harley-Davidson Motor Company certified Master Technician and avid biker, I love to write about everything and anything related to biking.

Click Here to Leave a Comment Below 2 comments
Bob - August 24, 2021

I bought the E3.36 spark plug that is supposed to be OK for my 2016 HD Sportster 1200C and the gap was totally wrong. You can’t really change the Gap on that spark plug.

Thanks for your time.


    Fender Bassman - June 16, 2023

    I put NGK plugs in my 1993 Sportster and it never ran again. Pulled them out, put them in my girlfriends 2007 FXDB and it never started. Put the burned out plugs back in, FXDB started. Sportster never recovered from NGK contamination. 3rd Sporty I’ve lost, my 1976 AMF was more dependable then the Evo trash.




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