Most Honda lawn mower engines use a 13/16-inch spark plug socket (20.6 mm) with a 3/8-inch drive. Some models may use a 5/8-inch or 14 mm hex size—verify with your plug or owner's manual.
Why the right socket matters
Using the correct size helps prevent stripping the plug head, ensures a proper seal when reinstalling, and fits the confined space under the mower’s housing. A poorly fitting socket can slip or leave residue that is hard to remove.
Common sizes you may encounter
Below is a quick guide to the sizes you might run into on Honda lawn mower engines. Always confirm with the model's manual or the spark plug you are using.
- 13/16 inch (20.6 mm) hex — the most common size for many Honda GX-series and similar engines.
- 5/8 inch (15.9 mm) hex — appears on some older or smaller engines or specific plug types.
- 14 mm hex (approximately 0.551 inches) — used with metric plugs; if your plug is metric, you may need a 14 mm spark plug socket.
To avoid errors, measure the plug's hex across flats with a ruler or calipers, or check the part number on the plug. The service manual for your mower model will also specify the correct size.
Practical tips for removing and reinstalling
Use a 3/8-inch drive ratchet with a rubber-insert spark plug socket to hold the plug securely. A swivel head can help reach tight spaces. Lightly lubricate the plug threads with anti-seize only if recommended by Honda; otherwise, let the plug threads be dry or use a thread lubricant as directed by the manual.
How to verify for your specific model
Identify your mower’s model number (often on the engine shroud or on the frame). Look up the official parts list or the owner's manual, or consult Honda’s support site to confirm the correct spark plug size for that model.
Conclusion
In most cases, you’ll need a 13/16-inch spark plug socket for Honda lawn mowers. If your plug’s hex is smaller or metric, switch to 5/8 inch or 14 mm accordingly, and always verify with the manual or the packaging.
Summary
Across Honda lawn mowers, the standard is typically a 13/16-inch spark plug socket. Alternatives exist for some older or metric plugs, such as 5/8-inch or 14 mm. When in doubt, check the mower's model-specific manual or the spark plug you intend to install.