A Comprehensive Guide to the Harley Davidson Spark Plug Chart

The spark plug chart is an essential tool for every Harley owner. It helps you determine the correct spark plug type and specifications for your motorcycle.

These specifications ensure optimal performance and fuel efficiency. Spark plugs are small devices that help ignition your motorcycle. They help burn the fuel well and ensure the engine’s smooth running. The Harley spark plug chart helps you choose the right one based on your bike’s specifications.

Here, take a comprehensive look at the Harley Davidson spark plug chart, how it can help optimize Performance, and what benefits you can reap from it. We will also include instructions on identifying the correct spark plug for your bike and replacing it safely and correctly.

Harley Davidson Spark Plug Chart

Types Of Spark Plugs

Types of Spark Plugs 

When Harley Davidson spark plugs, there are a few different options to choose from. It’s important to consult your motorcycle’s owner’s manual or speak with a knowledgeable mechanic to determine the best type of spark plug for your specific Harley Davidson model and riding style.

Proper maintenance, including regular inspection and replacement of spark plugs, is crucial for optimal engine performance. Here are the main types of spark plugs commonly used in Harley-Davidson motorcycles:

  • Standard Spark Plugs
  • Platinum Spark Plugs
  • Iridium Spark Plugs
  • Double Platinum Spark Plugs
  • High-Performance Spark Plugs

Use The Harley Davidson Spark Plug Chart For The Right Spark Plug

Use The Harley Davidson Spark Plug Chart For The Right Spark Plug

Harley-Davidson motorcycles have become an iconic American cultural symbol. Many Harley owners take pride in their bikes and are eager to keep them in top condition. To do so, they must know how to read the Harley Davidson spark plug chart.

This chart provides essential information about the spark plug required for every Harley Davidson model. It includes information on spark plug type, gap size, thread size, and reach. With this information, Harley owners can ensure that their motorcycles run at peak performance.

Spark plugs are tiny components in your engine that help convert fuel combustion into mechanical energy, allowing your vehicle to move. Engine performance and fuel efficiency improve with proper spark plugs. You can trust us to provide an in-depth understanding of these components. Let’s have a look at the Harley-Davidson spark plug chart:

  • ACCEL U-Groove
  • ACCEL Platinum
  • ACCEL Ref. No.
  • Champion
  • Harley-Davidson
  •  Model Number
Ref. No. Part No.        
2401 137 J12YC 3 N/A
2401A Y2401 138 J18YC 3-4 32301-60
2402A Y2402P 168 H10 5 32307-58
2403 115 N9YC 5-6 32309-69
2403A Y2403P 116 N12YC 5A6A 32310-78
2410* 494 RN9YC 5A6 32310-77
2410A* Y2410P 496 RN12YC 5R6A 32311-83
2413* Y2413P 453 RL82YC 4RS 32301-80
2418* Y2418P 882 RA8HC 6R12 32317-86
2418* Y2418P 882 RA8HC 6R12 32362-04

*Indicates Resistor Style Spark Plug

NOTE: ACCEL Reference Number is an actual number marked on the spark plug

How Do You Make Use Of A Spark Plug Chart?

How Do You Make Use Of A Spark Plug Chart

To make use of a spark plug chart, you need to understand the importance of spark plug specifications for optimal performance. The chart provides a reference guide for selecting the right spark plug based on factors such as pre-ignition and hotter spark plug requirements.

By referring to the chart, you can ensure that you choose the right spark plug that matches your engine’s needs, ultimately improving the overall performance of your vehicle. Here are some tips on how to make use of a spark plug chart effectively:

  • Understand the different spark plug codes.
  • Consult the manufacturer’s recommendations
  • Consider your riding conditions
  • Compare and cross-reference

Benefits Of Using The Right Spark Plug

Using the right spark plug can greatly improve the performance of your vehicle. Whether you are a casual rider or a professional racer, the choice of spark plug can make a significant difference. One benefit is the pre-ignition prevention provided by the HD-6R10 plug, ensuring a smooth and efficient combustion process. Another advantage is the heat range plug, which allows for optimal engine temperature control.

Additionally, the HD-6R12 spark plug offers a hotter spark, resulting in improved fuel combustion and power output. Finally, the grey colour and cooler plug design help dissipate heat more effectively, enhancing overall engine performance. Using the right spark plug in your Harley Davidson motorcycle can provide numerous benefits, including:

  • Improved engine performance
  • Increased fuel efficiency
  • Enhanced ignition system reliability
  • Extended engine life
  • Reduced emissions
  • Improved throttle response
  • Decreased risk of fouling
  • Enhanced cold-start Performance
  • Reduced maintenance needs
  • Optimal compatibility

How To Choose The Right Spark Plug For Your Bike

How To Choose The Right Spark Plug For Your Bike

 When choosing the right spark plug for your bike, there are a few important factors to consider. Firstly, consider the heat range. A colder spark plug, such as the HD-6R12 plug, is ideal for high-performance engines or those running at higher RPMs.

On the other hand, a warmer plug, like the HD-6R10, is better suited for engines operating at lower RPMs or in colder conditions. Additionally, the color of the spark plug can provide valuable information about the engine’s performance. A grey color indicates an optimal air-fuel mixture, while a white color suggests a lean mixture, and a black color indicates a rich mixture. Here are some key factors to consider when selecting a spark plug:

  • Heat range
  • Electrode material
  • Gap size
  • Thread size

You can make necessary adjustments to achieve optimal combustion by referencing the spark plug’s appearance. In conclusion, choosing the right spark plug is crucial for maintaining your bike’s performance and efficiency. Consider the heat range, inspect the color, and refer to the awesome Spark plug Reference to ensure you’re getting the best plug for your bike.

Maximizing Performance With The Spark Plug Chart

Maximizing Performance With The Spark Plug Chart

The spark plug chart is a valuable tool for maximising your engine’s performance. It provides information on plug temperature, heat range, and pre-ignition issues. By understanding these factors, you can choose the right spark plug for your engine‘s needs. If you want to enhance performance, opting for hotter spark plugs or oriental plugs designed for specific engines can make a difference.

Conversely, if you want to prevent overheating or reduce the risk of pre-ignition, colder plugs may be the solution. Additionally, considering the benefits of electronic ignition systems can further optimize your engine‘s performance. So, take the time to study the spark plug chart and make informed choices that will boost your engine‘s power and efficiency. Here are some tips for maximizing the Performance of your spark plug:

  • Replace a spark plug that’s burned out or fouled with one with higher sparks.
  • Maintain the gap between the spark plug and the cylinder head.
  • Clean and adjust the gap of your spark plugs regularly.
  • Check for loose or damaged parts regularly, including the spark plugs and lead wires.

How Does A Spark Plug Chart Help?

How Does A Spark Plug Chart Help

Spark plug charts are a valuable tool that can help optimise performance when changing spark plugs. They provide a visual representation of the condition of your spark plugs at different throttle conditions, which can help you identify areas for adjustments if rejecting your carburetors is necessary.

A spark plug chart helps in choosing the right spark plug for your application, whether it’s Iridium spark plugs or standard plugs. It ensures that during service, when using a torque wrench, you have the correct plug for your engine’s specific torque requirements. This chart takes into consideration different speeds and provides consistent Performance, meeting the H-D Standard.

By referring to the spark plug chart, you can avoid a compromised spark plug wire or using the wrong plug wire, ensuring optimal Performance with copper spark plugs. Spark plug charts are a valuable tool that can help you keep your motorcycle running smoothly and efficiently.


Spark Plugs are the electrical components that generate the spark that fuels an internal combustion engine. The spark plug of a Harley Davidson motorcycle is found in the leftmost cylinder of the engine and is fed by a metallic electrode called a spark plug boot.

The Harley Davidson Spark Plug Chart is a good way to identify the spark plugs that suit your motorcycle. It also helps you determine the correct spark plug gap for optimum Performance. We’ve provided you with a spark plug chart for Harley Davidson motorcycles, including information on the spark plugs used in each model. Following this chart, you can determine which spark plugs are right for your bike and keep it running smoothly and efficiently.

Frequently Asked Questions

What Size Are Harley Spark Plugs?

The spark plugs used in Harley Davidson motorcycles with 1999-2016 Twin Cam motors are typically a 5/8″ hex size. The size of the spark plug refers to its thread diameter, reach, and hex size.

How Do I Choose The Right Spark Plug?

When choosing the right spark plug, consider factors such as your vehicle’s – Wiring and engine type. Look for spark plugs with the correct heat range and thread size for your engine. The central electrode should be in good condition for optimal Performance.

How Do I Choose A Spark Plug For My Bike?

Look for a plug with the correct heat range and electrode design. Check the centre electrode for wear and black deposits, as these may indicate problems with the fuel or ignition system.

How Long Do Harley Spark Plugs Last?

Harley spark plugs typically last around 10,000 to 15,000 miles. Carbon deposits can build up on the spark plugs over time, affecting the Performance. 

What Is The Life Of Modern Spark Plugs?

The life of modern spark plugs can vary depending on factors such as the actual products and correct application. Generally, most spark plugs have a lifespan of around 30,000 to 100,000 miles.

Leave a Comment