A Guide To Honda GX25 Spark Plug Gap, Number & Socket Size

Just as a key is essential for unlocking a door, the right spark plug is crucial to ignite your Honda GX25 engine. That’s why understanding the specifications of your spark plug, including its gap, number, and socket size can be so beneficial.

This guide will serve as your ‘key’ to that knowledge. You’ll discover not only what these terms mean but also how they impact the performance of your machine. Armed with this information, you’ll feel more connected with your equipment and confident in its maintenance.

We’ll provide all the necessary details about Honda GX25 spark plug gap dimensions, part numbers, and appropriate socket sizes. Plus, we’ll even walk you through how to change out this vital component yourself if needed.

Welcome to an insider’s look at ensuring optimal performance from your Honda GX25 engine – let’s turn that key together!

A Guide To Honda Gx25 Spark Plug Gap, Number & Socket Size

Key Takeaways

  • The spark plug gap for the Honda GX25 engine should be set between 0.024″ and 0.028″.
  • The recommended spark plug types for the Honda GX25 engine are CM5H (NGK) or CMR5H (NGK).
  • Regular check-ups are necessary to ensure peak performance of the spark plug.
  • When replacing the spark plug, it is recommended to use NGK models CM5H or CMR5H with a gap setting of 0.024″ to 0.028″.
  • Owner´s manual – https://cdn.powerequipment.honda.com


You’ll be relieved to know that the spark plug gap for your HONDA GX25 engine is a mere 0.024′-0.028′, and the recommended type is either CM5H (NGK) or CMR5H (NGK), making maintenance a breeze!

This specific gap size ensures optimal performance, fuel efficiency, and longevity of your engine.

When replacing your spark plugs, it’s crucial to use the correct specifications as stated in the Owner’s Manual. Using an incorrect spark plug can lead to poor engine performance and potentially serious damage over time.

The right number for your model is either CM5H or its equivalent CMR5H by NGK – trusted names in spark plug technology.

Understanding these numbers may seem daunting at first, but don’t worry, you’re not alone! We understand that everyone wants their Honda engines running smoothly without any fuss. That’s why we provide detailed guides and professional advice based on accurate data from official Honda manuals.

Remember, regular check-ups on your spark plugs are essential for maintaining peak performance of your HONDA GX25 engine. So when it comes time to replace them, reach confidently for NGK models CM5H or CMR5H with a precise gap setting between 0.024’– 0.028′.

You’re part of a community that values quality and precision – embrace it!


To ensure a perfect fit when changing your engine’s spark plug, you’ll find that a 5/8′ (16mm) wrench is just what you need. This size of socket is explicitly recommended by Honda for the GX25 engine model. It provides the exact fit needed to remove and replace the spark plug without damaging it or the surrounding parts.

Here are three key reasons why using this specific socket size matters:

  1. Prevention of Damage: Utilizing an incorrect socket size can lead to improper fitting, which could damage your spark plug or engine.
  2. Efficient Removal and Installation: A 5/8′ (16mm) socket ensures easy removal and installation process, saving time during maintenance.
  3. Ensuring Engine Performance: Correctly installing spark plugs with a suitable tool helps maintain optimal engine performance.

By adhering strictly to these guidelines, you’re not only prolonging the life of your Honda GX25 engine but also ensuring its peak performance. Remember, investing in quality tools like a 5/8′ (16mm) wrench for your spark plug changes is part of taking pride in owning and maintaining such an excellent piece of machinery as your Honda GX25 engine.

How To Change Spark Plug?

Changing your engine’s spark plug isn’t as daunting as it might seem, and we’re here to walk you through every step of the way. With just a few tools and a bit of time, you can efficiently perform this essential maintenance task on your Honda GX25.

Here are the key steps:

Step 1Disconnect the spark plug wire. Be sure to do this gently to avoid damaging any parts.
Step 2Use a spark plug socket to remove the old spark plug. Remember, lefty loosey!
Step 3Gap your new spark plug properly. The gap should be set at 0.7-0.8mm for your Honda GX25 engine.
Step 4Install the new spark plug with your hands first, then tighten it using a torque wrench for precision fitment.

Remember that practice makes perfect so don’t feel discouraged if it doesn’t go perfectly smooth the first time around; soon enough you’ll be changing these like second nature! You’re part of our community now, and we believe in empowering each other with knowledge and guidance – one step at a time.

Frequently Asked Questions

What are the signs that indicate a need for Honda GX25 spark plug replacement?

Did you know 75% of engine problems are spark plug related? If your Honda GX25 is struggling to start, misfiring or has reduced fuel economy, it’s likely time for a spark plug replacement.

Can I use a different brand of spark plug for my Honda GX25?

Absolutely, you can use a different brand of spark plug for your Honda GX25. However, ensure it’s compatible and meets the required specifications. Incorrect plugs can lead to poor performance or even engine damage.

How often should I inspect the spark plug on my Honda GX25?

You should inspect your Honda GX25’s spark plug every 25 hours of operation or once a year, whichever comes first. Regular checks help maintain engine efficiency and prevent potential ignition problems.

Is it safe to clean and reuse a spark plug in a Honda GX25?

Yes, it’s safe to clean and reuse a spark plug in your Honda GX25. However, ensure it’s properly gapped. If excessively worn or damaged, replace it. Remember, a well-maintained spark plug optimizes engine performance.

What are the potential issues if the spark plug gap in my Honda GX25 is incorrect?

Even if you think it’s minor, an incorrect spark plug gap can cause engine misfires, power loss, poor fuel economy and even damage in your Honda GX25. So ensure it’s set correctly for smooth performance.


In the world of spark plugs, knowing your Honda GX25’s specifics is like holding the keys to the kingdom. It’s not just important, it’s essential! You’ve mastered the art of identifying the correct gap and number, and even deciphered that elusive socket size.

Now, you’re ready to tackle any spark plug change with gusto! You didn’t just learn something new today; you became a bona fide GX25 guru!

Bravo on this monumental achievement!

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