Harley Davidson Spark Plugs Cross Reference

The table below provides additional cross-reference information on replacement spark plug options for your Harley-Davidson. When shopping for a replacement spark plug option, have your OEM spark plug information handy, and you can reference it against the table to evaluate each option and determine which spark plug will work best for you.

Spark plugs are the underrated heroes of your motorcycle’s engine. They function as the conduit to generate the spark that ignites the fuel and air mixture, thereby creating the combustion that powers the motor. Without combustion, the engine on your Harley-Davidson would not be able to work, so it’s important to have the correct, compatible spark plug used in your motor.

There are four main types of spark plugs manufactured by Harley-Davidson that are available for most engines: a standard plug, Gold, Platinum, and Screamin’ Eagle spark plug option. Each of the types refers (either directly or indirectly) to the electrode material used in the plugs; the Harley-Davidson standard replacement spark plugs use copper electrode material, the Gold plugs are copper electrodes that are gold-plated, Platinum spark plugs use platinum electrodes, and Screamin’ Eagle spark plugs use double-coated platinum electrodes.

In turn, there are also aftermarket (non-HD) options that are available in the same thread as these spark plug types, although finding aftermarket gold spark plug options is less common; most offer copper, iridium, and platinum materials in their spark plug electrodes, and will be characterized by these primary materials. Copper is the most common material option due to it being the least expensive of the three materials to manufacture, although it is not nearly as durable compared to platinum and iridium options. Iridium takes top honors in durability, due to its conductivity and higher temperature tolerances, but Platinum plugs are considered just as premium as iridium plugs. Platinum plugs have the ability to handle high temperatures, and with it being a harder material than the others, make it a contender for a high-quality spark plug replacement option.

In addition to the electrode material, when you are considering a replacement spark plug option for your Harley-Davidson motorcycle, you will also need to know the dimensions for the thread, reach, and hex size for your original spark plug. “Thread” references the length of the actual threading on the tip of the spark plug, and is generally used in conjunction with thread pitch. This will determine how long the spark plug needs to be in order to thread in properly so it can ignite. “Reach” refers to the length of the thread from the base of the spark plug socket, where it screws into the head, all the way down to the tip where the electrode is located. Most Harley-Davidson spark plugs range from 12mm to 14mm thread, typically top out around 19mm reach, and are either 5/8” or 13/16” hex size.