The most common size is 13/16 inch, but some smaller or older Honda mowers use 5/8 inch. If you’re unsure, check the engine model or measure the spark plug hex to confirm.
Common socket sizes you may encounter
Most Honda mower engines fall into two sizes. The following guide helps you identify which one you’re likely to need before starting work.
- 13/16 inch (about 21 mm) spark plug socket: Fits the hex on the majority of Honda GX, GCV, and HR-series engines used on modern mowers.
- 5/8 inch (about 16 mm) spark plug socket: May be required on some smaller or older Honda engines; always verify by checking the plug hex size before forcing a fit.
In practice, starting with the 13/16-inch socket covers most contemporary Honda mowers. If it doesn’t seat properly, try the 5/8-inch size rather than applying extra force.
How to confirm the correct size for your exact mower
To ensure you use the right socket for your specific model, follow these verification steps and consult official documentation if needed.
- Identify your engine model (for example, GCV or GX series) and locate the owner’s manual or Honda support page for the recommended spark plug size and gap.
- Remove any debris around the spark plug and disconnect the spark plug wire before handling the plug itself.
- Line up the spark plug hex with a 13/16" socket; if it doesn’t fit snugly, try the 5/8" socket and attempt again with care to avoid stripping the hex.
- If still unsure, remove the plug and measure the hex across flats with a caliper or a gauge, then match to the closest standard size (inches or millimeters).
- When in doubt, bring the plug or engine model information to a local parts retailer to get a precise match.
Accurate sizing helps prevent cam-out and damage, and ensures you can safely remove, inspect, or replace the spark plug during routine maintenance.
Tips and cautions
Practical reminders to help you work safely and effectively when servicing your Honda mower.
- Always use the correct size to avoid damaging the plug’s hex or the socket.
- Work with the engine cool and disconnect the spark plug wire before handling the spark plug.
- Use a spark plug socket with a rubber insert for a secure grip on the plug and to minimize drops.
- After replacing, check the plug gap according to the manufacturer’s specification and replace with the recommended heat range and type (NGK, Champion, etc.).
With the right socket, maintenance becomes quicker and reduces the risk of mis-sizing or cross-threading while changing spark plugs.
Summary
For most Honda mowers, you’ll use a 13/16-inch spark plug socket, with 5/8 inch as an alternative for certain smaller or older engines. Always verify by checking your engine model’s manual or measuring the spark plug hex, and follow safety steps when servicing the plug. Keeping both sizes on hand covers the majority of Honda mower models in use today.
Are all spark plugs 14mm?
For the majority of plugs, you need a 5/8” or 16mm socket. Some Fords use 9/16″ plugs, some newer European and Asian vehicles use 14mm plugs, and there are a few applications that use 7/8″, 13/16″, ¾” or 18mm plugs. All spark plugs are 6 sided, except some BMW engines.
What spark plug do I need for a Honda lawn mower?
NGK BPR5ES
Product details
NGK BPR5ES Standard spark plug. Recommended for reliable performance for most automotive and non-automotive applications. OEM replacement plug for many Honda small engines in lawn and garden equipment.
What size socket for Honda mower spark plugs?
If you don't have a 13/16. And uh this one's a deepwalled for a spark plug so I ordered this off of Amazon it's a Tekon brand.
Are all lawn mower spark plugs the same socket size?
Socket wrench with a spark plug socket: Most lawn mowers use either a 13/16-inch or ⅝-inch spark plug socket. Ratchet or adjustable wrench: To turn the socket. Spark plug gap gauge: To check and adjust the gap on the new spark plug. Wire brush or rag: To clean around the plug.