The standard size for most Honda spark plugs is a 14mm hex, which requires a 14mm spark plug socket (deep-well) to remove and install the plug. This size covers the vast majority of Honda cars, motorcycles, and many small engines. Some very old or specialized Honda engines may use different sizes, so always confirm with your model’s service manual or by inspecting the plug itself.
Understanding the typical size
Most Honda engines use a 14mm across-flats hex on the spark plug. The corresponding tool is a 14mm spark plug socket, typically a deep-well style to reach plugs tucked in tight spaces. The drive size (the ratchet connection) is usually 3/8" or 1/2", depending on your toolkit and the space around the plug.
Model variations to watch for
While 14mm is by far the most common size for Honda spark plugs, there are exceptions, especially on older appliances or very specialized equipment. If you’re working on an older Honda lawn mower, generator, or a less common Honda engine, verify the plug hex size before purchasing a socket. When in doubt, remove the plug and measure the hex across flats or check the engine’s service manual.
Before you assemble your toolkit for a plug change, here is what you’ll typically need.
- 14mm spark plug socket (preferably deep-well) with a rubber insert to hold the plug securely
- Ratchet (3/8" drive is common) and an extension bar for reach
- Torque wrench to apply the correct reinstall torque (follow the model’s specification)
- Optional anti-seize compound on new plugs (use sparingly and per manual)
This toolkit covers the standard Honda spark plug replacement tasks. Always tailor the kit to your model and follow the manufacturer’s guidance for torque and seating.
Steps to replace a spark plug on a typical Honda engine
Here are general steps you can follow to replace a spark plug. Always consult your specific model’s service manual for torque specifications and any model-specific instructions.
- Disconnect the battery ground cable if you’re working on a vehicle to avoid any electrical shorts.
- Locate the spark plug wire or coil pack and carefully disconnect it from the plug.
- Clean around the spark plug to prevent dirt from entering the combustion chamber during removal.
- Using the 14mm spark plug socket with a properly sized extension, loosen and remove the old plug by turning counterclockwise.
- Check the gap on the new spark plug and install it to the manufacturer’s torque specification, then reconnect the ignition lead.
After executing these steps, recheck that everything is seated properly and test the engine to ensure it runs smoothly. If you encounter any misfires or abnormal sounds, consult the service manual or a professional mechanic.
Summary
For most Honda applications, a 14mm spark plug socket is the correct choice. Always confirm by checking the engine’s service manual or the plug itself, since a small number of Honda engines may use different hex sizes. With the right socket, a ratchet, an extension, and a torque wrench, you can safely remove and replace spark plugs to maintain optimal engine performance.