Honda GX120 Spark Plug Gap, Number & Socket Size Guide

Imagine the thrill of perfecting your Honda GX120 engine performance, and the satisfaction in knowing you’ve done it yourself.

This article is your comprehensive guide to understanding every detail about the Honda GX120 spark plug gap, number, and socket size for your. With meticulous attention to detail and precise specifications, you can maximize engine efficiency and ensure long-lasting performance.

You’ll have access to technical insights drawn from extensive hands-on experience and research-based knowledge. So whether you’re a seasoned mechanic or an enthusiastic beginner eager to roll up your sleeves, this guide will equip you with all the know-how needed.

By doing this together as a community of Honda GX120 aficionados, we foster a sense of belonging while empowering each other with practical skills.

Brace yourself for an enriching journey into the world of engine maintenance that’s not just about fixing things but more about mastering them.

Guide To Honda GX120 Spark Plug Gap, Number & Socket Size Guide

Key Takeaways

  • NGK BPR6ES or DENSO W20EPR-U spark plugs are recommended for the Honda GX120 engine.
  • The spark plugs are designed to withstand the heat range and compression ratio of the engine.
  • They offer excellent resistance against fouling and have anti-corrosion characteristics.
  • It is recommended to use a 13/16′ (21mm) socket size for changing the spark plug.
  • Owner´s manual –


You’ll need the BPR6ES (NGK) 98079-56846 or W20EPR-U (DENSO) 98079-56855 spark plug for your Honda GX120, and make sure you’ve got that gap set just right between 0.028″– 0.031″—it’s crucial for optimal performance!

It’s not just about picking up any old spark plug; this is about choosing a component that’s compatible with your engine. As every proud Honda GX120 owner knows, each part needs to work harmoniously to ensure smooth operation.

The specified gap between the center electrode and ground electrode of your spark plug plays a key role in the ignition process. This precise distance controls the electric discharge for igniting the air-fuel mixture within the engine cylinders. If you don’t get this right, it could lead to less efficient combustion, potentially reducing power output and fuel economy.

Furthermore, using either NGK BPR6ES or DENSO W20EPR-U ensures perfect compatibility with your Honda GX120 engine. These plugs are specifically designed to withstand its heat range and compression ratio. They also offer excellent resistance against fouling while providing superior anti-corrosion characteristics.

So remember, you’re making an investment in quality parts that’ll help maintain the integrity of your beloved Honda GX120, keeping it running efficiently for years to come.


When it comes to changing your engine’s life force, you’re essentially cracking open a knight’s helmet with a 13/16′ (21mm) tool – the perfect fit for this job. This is no random choice; Honda engineers have meticulously calculated that this dimension will securely grip and maneuver your spark plug without causing undue stress or damage.

Understanding the right socket size is crucial in maintaining your Honda GX120 engine. This isn’t just about replacing an old spark plug, but nurturing an essential component of your machine. The 13/16′ (21mm) socket size ensures that you can properly install or remove the BPR6ES (NGK) 98079-56846 / W20EPR-U (DENSO) 98079-56855 spark plug or its equivalent.

Imagine yourself as part of a community of dedicated Honda enthusiasts who appreciate precision and accuracy as much as speed and performance. You aren’t just executing a routine maintenance task but engaging in an intricate mechanical dance that contributes to keeping your beloved engine humming smoothly.

Remember, using the right tool for this delicate operation allows you to respect and preserve the integrity of your machine. So, when it’s time to service your Honda GX120 engine again, don’t forget: wield that 13/16′ (21mm) socket like a knight wielding his trusty sword!

Frequently Asked Questions

What is the average lifespan of a spark plug in a Honda GX120?

While it’s not set in stone, your Honda GX120 spark plug should typically last around 2 years. However, this can vary based on usage and maintenance practices. Regular checks are always a good idea.

How does the performance of the Honda GX120 get affected if the spark plug gap is incorrect?

Imagine trying to start a fire with wet kindling; that’s what it feels like when your GX120’s spark plug gap is off. The engine may misfire, run rough, decrease fuel efficiency, or even fail to start.

What are the signs of a faulty spark plug in a Honda GX120?

You might notice a decrease in your GX120’s performance, with symptoms like rough idling, difficulty starting, high fuel consumption or misfires. These are common signs of a faulty spark plug that needs replacement.

Are there any specific brands of spark plugs recommended for use in a Honda GX120?

Navigating the sea of spark plug brands can be challenging. For your Honda GX120, it’s best to stick with NGK or Bosch plugs. They’re top-notch, ensuring optimal performance and longevity for your engine’s needs.

How frequently should the spark plug be replaced in a Honda GX120?

For optimal engine performance in your Honda GX120, it’s recommended to replace the spark plug every 100 hours of use or annually, whichever comes first. Regular maintenance ensures your machine performs efficiently and reliably.


Just like a key is to a lock, the right spark plug gap and number are crucial for your Honda GX120. Ensure you’re using a 0.7-0.8 mm gap with an NGK BPR6ES or equivalent. Your socket size should be 13/16′.

With this guide, you’ll have your engine purring like a well-fed cat in no time! Always remember, accuracy is paramount when dealing with technical specs, it’s your ticket to peak performance.

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