Buyer's Guide & Information

Best Spark Plugs For Harley Davidsons Reviewed

Get the most efficiency out of your Harley Davidson motorcycle with these top-rated spark plugs.

If you want to get the most efficiency out of your Harley Davidson motorcycle, then you need the right kind of spark plugs. Good quality quality spark plugs will help maintain your engine’s life and contribute to your overall fuel economy.

So we put together this comprehensive guide on the 6 best spark plugs for Harley Davidson motorcycles to help you make the best choice.

Spark plugs create the electrical spark that ignites the gas, allowing your motor to work. Over time, your stock spark plugs can lose their power and become inefficient. Replacing bad or worn spark plugs can extend the life of your motorcycle, increase your horsepower and acceleration, contribute to better fuel economy, and reduce the chance of engine failure.

Over time, the components of your spark plugs will degrade and might break. There are a few key signs you can look for to tell if your spark plugs need replacing, including but not limited to:

  • Trouble starting the engine
  • Misfiring engine
  • Poor fuel economy
  • Loud engine idling
  • Reduced acceleration and horsepower
  • Extremely loud engine activity

If you notice any of these issues, then that could mean that you need to replace your spark plugs. Riding on a bad spark plug can cause severe engine damage, which could rack up thousands of dollars in maintenance costs. So it’s in your best interest to keep them in tip-top shape.


Spark Plugs for Harley Davidsons Compared

Preview

Product

Compatible Harleys

Plug Type/Number

Gap Size

Check Price

NGK # 6046 Iridium Spark Plugs -- DCPR7EIX --...

NGK #6064

Twin Cam 88”/96”, V-rod, EVO 1340 80”, XL Sportster 883/1200

A

0.8mm = 0.032"

E3 Spark Plugs E3.36 Powersports Spark Plug...

E3 Spark Plugs E336

Road King, Screaming Eagle, Electra Glide, CVO Ultra Classic, Tri-Glide, Fat Boy, Softail, Road Glide, Fat Bob

A

0.028”

NGK 6046 DCPR7EIX Spark Plug (Pack of 2)

NGK 6064 DCPR7EIX

Road King, Twin Cam, EVO 1340 80”, XL Sportster, Shovelhead, XR 1000, Sportster Ironhead, Buell Blast

A

0.032"

NGK Iridium IX DCPR7EIX Spark Plugs for...

NGK Iridium IX DCPR7EIX

Dyna, Fat Bob, Low Rider, Glide custom, Softail Classic, Road Glide, Road King, Sportster, Street Bob, Tri Glide

A

0.032"

Iridium Performance Spark Plugs Pair for...

Orange Cycle Parts Harley #6R12

Softail

A

0.032"

Champion 810 Spark Plugs 2 Pack

Champion 810

Twin Cam, XL Sportster, Blackline, CrossBones, Dyna, Electra Glide

A

0.022"-0.028"


Spark Plug Buyer's Guide for Harley Davidson Motorcycles

Compatibility

You first need to make sure that your desired spark plug is compatible with the make & model and the age of your vehicle. For example, a spark plug designed for a 60 cc knucklehead engine will not work with a shovelhead 82cc engine and vice versa. Using the wrong spark plug can cause a whole host of engine issues.

Spark plug coating

The coating of a spark plug provides necessary electrical resistance. There are 3 main types of spark plug coating:

  • Copper
  • Iridium
  • Platinum

For the most part, you want to stick to iridium spark plugs for your Harley Davidson. Iridium is a strong material that can withstand a lot of electrical resistance. However, some varieties of platinum spark plugs can serve very well. You will want to avoid copper spark plugs, though, as these are not as high quality as iridium or platinum ones.

Build quality & functionality

The best spark plugs are made from durable precious metals such as platinum and iridium. These metals have very high melting points and can handle a lot of electrical resistance before failing. Additional, good quality spark plugs generally have ceramic insulators.

Heat range & insulation

Spark plugs are rated for a particular temperature operation. Most spark plugs only work when their internal electrode temperature is between 500-950 degrees-C. Thus spark plugs also require good insulation to keep the heat from leaking. In general, high-quality spark plugs have ceramic insulation. Ceramic has high heat retention and is extremely durable.

Thread size & gap style

The threads determine how the spark plug screws into the port while the gap refers to the space where the electrical discharge occurs. Spark plug gaps should never exceed 0.055" unless specified by the manufacturer. There are currently three thread sizes used for motorcycle spark plugs:

  • 10mm x 1.0mm
  • 12mm x 1.25mm
  • 14mm x 1.25mm

Lifespan & mileage

Most motorcycle spark plugs are designed to last for at least 15,000 miles, or about once every 1-2 years or so, depending on how often you ride it. The more you ride your motorcycle, the more frequently you will have to replace your spark plugs. You should never ride more than 30,000 miles without changing your spark plugs.

Price & warranty

Most motorcycle spark plugs will cost between $20 on the low end to $90-$150 on the high end. Most of the time, copper spark plugs are the cheapest, while iridium and platinum spark plugs are more expensive. You should also look for spark plugs that have a warranty agreement so you can get a replacement in case they fail.


6 Best Spark Plugs for Harley Davidsons Reviewed

1. NGK #6064

Best Spark Plugs for Harley Davidson

Compatible Harleys

Twin Cam 88”/96”, V-rod, EVO 1340 80”, XL Sportster 883/1200

Plug Material Coating

Iridium

Top Material

Nickel alloy

Plug Type/Number

A

Gap Type/Size

0.8mm = 0.032 in

First up on our list is the NGK #6064. These spark plugs feature an iridium coating and are designed for the Harley Twin Cam and XL. This package comes with 4 separate spark plugs and is designed to give your engine more power, performance, and fuel economy. The highly advanced iridium spark plugs are 25% smaller than comparable platinum electrodes and nearly ¼ of the size of comparable nickel electrodes. The ultrasmall diameter center electrode reduces voltage requirements and also has the dual function of extending the ignition systems' life. The iridium coating also has anti-corrosive properties. 

The NGKs have a thread size of 14mm, slightly larger than the average thread size for most Harleys. They are pre-gapped, so you do not have to worry about setting that yourself.  At the very least, these spark plugs can last you up to 15,000 miles, potentially even more if you perform regular engine maintenance.

These spark plugs also have a special taper-cut ground electrode that allows for more area for faster flame expansion when firing up the engine. The fine-wire iridium center electrode ensures a very high level of durability and consistent spark creation. The metal coating also has special anti-seizing properties for smooth acceleration and torque.

Pros

  • Iridium coating is high quality
  • Removable nut
  • High heat range
  • Anti-corrosion and anti-seizing properties

Cons

  • Very small
  • Slightly pricey

2. E3 Spark Plugs E336

Best Performance Spark Plugs for Harley Davidson

Compatible Harleys

Road King, Screaming Eagle, Electra Glide, CVO Ultra Classic, Tri-Glide, Fat Boy, Softail, Road Glide, Fat Bob,

Plug Material Coating

Copper

Top Material

Nickel

Plug Type/Number

A

Gap Type/Size

0.028”

Up in second place is the E3 Spark Plug E336. These high-performance spark plugs are favored by racing professionals for their high-quality and superior acceleration. They use a specially designed colder heat range that enables performance modifications and handling in intense conditions. The E3 contains a Ytterbium-enhanced alloy that allows for up to an 8% reduction in side wire temperature, which provides for improved resistance and durability. These spark plugs have a thread diameter of 12mm and a thread reach of 0.750”, along with a hex size of ⅝ inch.

These spark plugs are not only compatible with most existing Harley Davidson models but also with cars and trucks too. These spark plugs use a heavy-duty copper coating, which is extremely durable, and a center electrode design that allows for consistent temperatures for electrode firing. They are also pre-gapped, so you do not have to worry about setting it yourself. The E3 is equipped to minimize venting of fuel by burning the fuel more efficiently. It can provide new performance and life to your engine.

These spark plugs are also very environmentally friendly and can be recycled as they are not made with any toxic metal components. They can provide more power, improved fuel economy, and longer engine life.

Pros

  • Very affordably
  • Burns fuel efficiently
  • Pre-gapped
  • Nickel tip electrode

Cons

  • Copper coating
  • Very small

3. NGK 6064 DCPR7EIX

Best Spark Plugs for Harley Davidson Road King

Compatible Harleys

Road King, Twin Cam, EVO 1340 80”, XL Sportster, Shovelhead, XR 1000, Sportster Ironhead, Buell Blast

Plug Material Coating

Iridium

Top Material

Iridium

Plug Type/Number

A

Gap Type/Size

0.032 in

Up next is another from NGK, this one the DCPR7EIX. This spark plug features a durable iridium coating and is designed with the performance enthusiast in mind. These iridium spark plugs offer extreme ignitability, improved throttle response, and anti-fouling. The center-electrode design ensures consistent firing and minimum heat leakage along with a consistent spark. Since iridium has a very high melting point, these spark plugs are designed for modern high-performance engines and do not slack on power.

They also have a special taper-cut ground electrode shape that enlarges the gap area for faster and more efficient flame expansion. Trivalent plating has anti-corrosion and anti-seizing properties. The pure aluminum silica ceramic insulator provides superior strength and better heat transfer. It also has a durable copper core that assists in heat removal while the triple-sealed design prevents and leaking of unburnt fuel.

Overall, the NGK hits it out of the park with these spark plugs. They can offer superior performance and extend the life of your Harley's engine. They are also extremely affordable, considering the design and quality of the materials. They are some of the best spark plugs you can buy for the money, which is why they won our pick for the best spark plugs for the Harley Davidson Road King.

Pros

  • Excellent quality
  • Best for the road king
  • Pre-gapped design
  • Triple sealed casing prevents leakage

Cons

  • Quality control issues
  • Does not handle dielectric grease well

4. NGK Iridium IX DCPR7EIX

Best Spark Plugs for Harley Davidson Twin Cam

Compatible Harleys

Dyna, Fat Bob, Low Rider, Glide custom, Softail Classic, Road Glide, Road King, Sportster, Street Bob, Tri Glide

Plug Material Coating

Iridium

Top Material

Nickel

Plug Type/Number

A

Gap Type/Size

0.032 in

Up in fourth place is another contender from NGK, this on the Iridium IX DCPR7EIX. This variety of NGK features an Iridium coating and nickel core electrode, which allows for high performance and low corrosion risk. These spark plugs are 25% smaller than a platinum electrode and also smaller than a conventional nickel electrode. The NGK Iridium also has an ultra-small diameter center electrode, which allows for more efficient ignition systems and a reduction in required voltage. This new model of NGK spark plugs has a special multi-shell coating that reduces corrosion and prevents leaking of unburnt fuel, thus increasing overall engine efficiency.

At just 0.12 lbs, these spark plugs are ultra-light and noninvasive. They are easy to replace and have a heat range of 7, indicating a wide range of temperature operation levels. The nickel alloy electrode has a very high heat resistance, and the single electrode configuration makes them simple to install. You can also remove the terminal with the removable nut design. Like the other spark plugs in the NGK family, this version also has a taper-cut ground electrode that provides a larger area for faster and more efficient flame expansion. 

Pros

  • Iridium coating has a high heat resistance
  • Small size is easy to replace
  • Pre-set gap
  • Triple sealed

Cons

  • Quality control issues
  • Gap is not adjustable

5. Orange Cycle Parts Harley #6R12

Best Spark Plugs for Harley Softail

Compatible Harleys

Softail

Plug Material Coating

Iridium

Top Material

Nickel

Plug Type/Number

A

Gap Type/Size

0.032 in

The next to last entry on our list is the Orange Cycle Parts Harley #6R12. These spark plugs market themselves as the ultimate in spark plug technology and features an iridium coating that is smaller than the standard electrode. The smaller electrode means that it requires less resistance to getting started. It also means that it can generate a hotter spark, which allows for more efficient fuel burning. They can extend your engine life for a long time. They also have a very distinctive black ceramic and gold-colored coating on the metal shell, which is a very nice aesthetic touch, to be sure. They also have a standard 12mm thread, so they will fit most Harley models. 

These spark plugs won our pick for the best spark plugs for the Harley-Davidson Softail due to its superior constriction, and it has an insulator made out of 95% pure alumina ceramic These spark plugs are also pre-gapped, so you do not have to spend time adjusting it. Overall, these spark plugs are an excellent choice for your Softail and can help extend your engine life and improve your fuel economy. The iridium components have a very high heat tolerance and also have anti-corrosive and anti-seizing properties.

Pros

  • Unique appearance
  • Anti-corrosive and anti-seizing properties
  • Small electrode generates more heat
  • Reduced voltage requirements

Cons

  • No very compatible with Harley models
  • Quality control issues with the manufacturer

6. Champion 810

Best Spark Plugs for The Money

Compatible Harleys

Twin Cam, XL Sportster, Blackline, CrossBones, Dyna, Electra Glide,

Plug Material Coating

Copper

Top Material

Nickel alloy

Plug Type/Number

A

Gap Type/Size

0.022-0.028 in.

Last but certainly not least on our list is the Champion 810 spark plugs. These spark plugs feature a copper core and heavy-duty electrode for superior performance. The 810 is designed and created by Champion, which is well known in the automobile industry for its high-quality parts and engine components. The Champion has a triple-coated shell that prevents wasting fuel by making the engine burn more efficiently. It also has precision rolled threads that abide by all industry specifications. The copper core is heavy-duty and extends the spark plug's overall life.

The Champion 810 also has RFI (radio frequency interference) suppression to protect other sensitive electrical components in the car. The heavy-duty materials can resist overheating under heavy engine loads. The 810 is also extremely affordable and makes an excellent spark plug you can buy without breaking the bank. With its superior corrosion resistance, it can resist engine fouling. The copper electrode also has increased conductivity and heat control, which reduces overall wear and tear.

Overall, the Champion 810 makes an excellent product to finish off our list with its heavy-duty components and superior construction. Its affordability and low price only make it that much better of a choice for your Harley.

Pros

  • Extremely affordable
  • Heavy-duty copper has high resistance
  • Pre gapped
  • Great brand reputation

Cons

  • Threads are hard to screw
  • Quality control issues

How to Replace Harley Davidson Spark Plugs

First, remove the fuel tank from your motorcycle to access the engine. Next, you will have to remove the spark plug wires and unscrew the plug from its socket. Be very careful when taking out the wires and use a pair of spark plug pliers. Also, make sure that you keep the spark plug socket free from any debris.

You can start screwing in the spark plugs by hand, ensuring that you are leaving the correct gap as specified by the manufacturer. Do not screw them in too tight as you do not actually want the bottom to make contact with the socket. Next, apply a small bit of dielectric grease and reattach the wires.


People Also Ask (FAQs)

Who makes Harley Davidson spark plugs?

Lots of different companies make spark plugs compatible with Harley Davidson motorcycles, including the company itself.

Does the brand of Harley spark plugs matter?

Strictly speaking, no. As long as it is compatible with your model, the brand should not matter. That being said, some brands make better spark plugs than others.

How do I know what gap size I need?

Your specific Harley has a required gap size. Consult a Harley Davidson spark plug gap chart to figure out which gap size you need.

What color should my Harley spark plugs be?

Color doesn't really matter so much, but the most common colors for Harley spark plugs are white and blue.

How often should spark plugs be replaced on a Harley Davidson?

Harley recommends changing spark plugs once every 15,000 miles or about once every 1-2 years.

How many spark plugs does a Harley Davidson need?

It depends on the specific type of bike, but most motorcycles, Harleys included, have anywhere between 2-6 spark plugs.

Where is the best place to buy replacement spark plugs for Harley Davidson?

There are a lot of places to buy Harley spark plugs, but some of the best places include online retailers like Amazon.


Conclusion

According to our roundup, the best spark plug for Harley Davidson motorcycles is the NGK #6064 because of its durable iridium coating, triple-sealed coating that minimizes leakage, and overall performance quality. If you are looking for a solid set of spark plugs that can increase your engine life, then the NGK is the way to go.

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