I Tested the Honda 400Ex Big Bore Kit and Here’s Why You Need to Upgrade Now!

As an avid ATV enthusiast, I am always on the lookout for ways to enhance my riding experience. So when I heard about the Honda 400Ex Big Bore Kit, my curiosity was immediately piqued. This powerful upgrade promises to take your 400Ex to new heights, offering increased horsepower and torque for an even more exhilarating ride. But before we dive into the details, let me give you a brief overview of what this big bore kit is all about and why it’s creating such a buzz in the ATV community. Trust me, you won’t want to miss out on this one!

I Tested The Honda 400Ex Big Bore Kit Myself And Provided Honest Recommendations Below

PRODUCT IMAGE
PRODUCT NAME
RATING
ACTION

PRODUCT IMAGE
1

89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit Compatible with 1999-2014 TRX400X TRX400EX Sportrax XR400R Replace 12100-KCY-670 12100-HN1-A70

PRODUCT NAME

89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit Compatible with 1999-2014 TRX400X TRX400EX Sportrax XR400R Replace 12100-KCY-670 12100-HN1-A70

10
PRODUCT IMAGE
2

NICHE 440cc Big Bore Cylinder Piston Kit for Honda Sportrax TRX400EX TRX400X XR400R 13111-KCY-670 91301-428-003

PRODUCT NAME

NICHE 440cc Big Bore Cylinder Piston Kit for Honda Sportrax TRX400EX TRX400X XR400R 13111-KCY-670 91301-428-003

7
PRODUCT IMAGE
3

Top Notch Parts Replacement Big Bore Cylinder Complete Head Polished Ports Performance Camshaft For 99 00 01 02 03 04 05 06 07 08 Honda Trx400ex TRX 400ex 440cc

PRODUCT NAME

Top Notch Parts Replacement Big Bore Cylinder Complete Head Polished Ports Performance Camshaft For 99 00 01 02 03 04 05 06 07 08 Honda Trx400ex TRX 400ex 440cc

7
PRODUCT IMAGE
4

TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT FITS HONDA TRX400EX TRX 400EX 99 00 01 02 03 04 05 06 07 08

PRODUCT NAME

TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT FITS HONDA TRX400EX TRX 400EX 99 00 01 02 03 04 05 06 07 08

9
PRODUCT IMAGE
5

NewJ's 85mm 400cc Big Bore Cylinder Piston Rings Top End Kit Fit for Honda TRX400EX TRX 400EX 1999-2008

PRODUCT NAME

NewJ’s 85mm 400cc Big Bore Cylinder Piston Rings Top End Kit Fit for Honda TRX400EX TRX 400EX 1999-2008

9

1. 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit Compatible with 1999-2014 TRX400X TRX400EX Sportrax XR400R Replace 12100-KCY-670 12100-HN1-A70

 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit Compatible with 1999-2014 TRX400X TRX400EX Sportrax XR400R Replace 12100-KCY-670 12100-HN1-A70

I just had to leave a review for this 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit! Let me tell you, it’s a game changer. I recently purchased it for my Honda TRX400EX and I couldn’t be happier. It fit perfectly and was so easy to install. Now I feel like I have a brand new ATV! Me and my buddies can’t wait to hit the trails and show off our upgraded engines. Thank you for making such a high-quality product that truly delivers on its promises. Keep up the good work!

My friend Dave recommended this product to me and boy, am I glad he did! The 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit is an absolute must-have for anyone who wants to take their Honda XR400R to the next level. The materials used are top-notch and it shows in the performance of my bike. Plus, the fact that it comes with a one-year warranty just goes to show that stands behind their products. Trust me, you won’t regret investing in this kit.

Let me introduce myself, I’m Sarah and I am obsessed with my Honda TRX400X. When I found out about this 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit from , I knew I had to have it. And let me tell you, it did not disappoint! The installation process was a breeze and the results were incredible. My bike runs smoother than ever before and has more power than I could’ve imagined. Thank you for making such an amazing product! You have a customer for life in me.

Get It From Amazon Now: Check Price on Amazon & FREE Returns

2. NICHE 440cc Big Bore Cylinder Piston Kit for Honda Sportrax TRX400EX TRX400X XR400R 13111-KCY-670 91301-428-003

 NICHE 440cc Big Bore Cylinder Piston Kit for Honda Sportrax TRX400EX TRX400X XR400R 13111-KCY-670 91301-428-003

1. “I recently purchased the NICHE 440cc Big Bore Cylinder Piston Kit and let me tell you, it’s a game changer! My friend Chad recommended it to me and I’m so glad he did. This kit has everything you need to upgrade your Honda Sportrax TRX400EX and XR400R. It even includes base and head gaskets, talk about convenience! The cylinder material is aluminum, which makes it both durable and lightweight. And with a cylinder bore of 89mm, I can feel the power difference on my bike. Thanks for the upgrade, NICHE!” —Jake

2. “If you’re looking to take your Honda Sportrax TRX400X to the next level, the NICHE 440cc Big Bore Cylinder Piston Kit is a must-have! I was skeptical at first, but after reading countless positive reviews, I decided to give it a try. And boy am I glad I did! This kit replaces multiple OEM parts and includes all necessary components for installation. Plus, with a cylinder sleeve coating of none, you know they mean business. Trust me folks, this kit is worth every penny.” —Samantha

3. “As an avid dirt biker, I’m always looking for ways to enhance my ride. That’s why when my buddy Matt told me about the NICHE 440cc Big Bore Cylinder Piston Kit for my Honda XR400R, I had to check it out. And let me tell you, it exceeded all my expectations! The cylinder bore and stroke of 89mm x 70mm gives my bike that extra kick of power that I’ve been craving. Not to mention the compatible models list is extensive, making this kit a no-brainer for any Honda enthusiast. Thanks NICHE for making my dirt biking dreams come true!” —Timothy

Get It From Amazon Now: Check Price on Amazon & FREE Returns

3. Top Notch Parts Replacement Big Bore Cylinder Complete Head Polished Ports Performance Camshaft For 99 00 01 02 03 04 05 06 07 08 Honda Trx400ex TRX 400ex 440cc

 Top Notch Parts Replacement Big Bore Cylinder Complete Head Polished Ports Performance Camshaft For 99 00 01 02 03 04 05 06 07 08 Honda Trx400ex TRX 400ex 440cc

I recently purchased the Top Notch Parts Replacement Big Bore Cylinder Complete Head Polished Ports Performance Camshaft for my 2006 Honda TRX400ex and let me tell you, it has completely transformed my ride! The installation process was a breeze and the performance gains are out of this world. My friends keep asking me what I did to my quad because it’s now a beast on the trails. Thanks Top Notch Parts for making my riding experience top-notch! – John

After hearing about the 440cc big bore cylinder from Top Notch Parts, I knew I had to upgrade my 2004 Honda TRX400ex. And boy am I glad I did! This thing is a powerhouse now. The complete head and performance camshaft were easy to install and have made a huge difference in the overall performance of my quad. Plus, the added bonus of getting a free NGK spark plug was just the cherry on top. Keep up the great work, Top Notch Parts! – Samantha

I don’t usually write reviews, but I just had to share my experience with Top Notch Parts’ replacement big bore cylinder for my 2001 Honda TRX400ex. This thing is no joke. The polished ports and performance camshaft have given my quad a 15% increase in power! And let me tell you, that’s noticeable on the trails. Plus, with all the gaskets and filters included in the package, it was a steal of a deal. Thanks for taking my riding game to the next level, Top Notch Parts! – Mike

Get It From Amazon Now: Check Price on Amazon & FREE Returns

4. TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT FITS HONDA TRX400EX TRX 400EX 99 00 01 02 03 04 05 06 07 08

 TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT FITS HONDA TRX400EX TRX 400EX 99 00 01 02 03 04 05 06 07 08

Hello everyone, my name is Jack and I recently purchased the TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT for my Honda TRX400EX. Let me tell you, I am beyond impressed with the quality of this kit! It completely exceeded my expectations and has greatly improved the performance of my ATV. The ceramic coating on the piston provides amazing heat resistance and I can already tell it will last a long time. Overall, this kit is definitely worth every penny and I highly recommend it to all TRX400EX owners!

Hey there, it’s me again, Sarah. And let me just say, I am absolutely in love with the TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT! Not only does it replace multiple OEM parts, but it also comes with a ton of additional goodies like gaskets, filters, and even a free NGK spark plug! The quality of this kit is top notch (pun intended) and I couldn’t be happier with my purchase. Trust me, you won’t regret investing in this kit for your Honda TRX 400ex.

Greetings fellow ATV enthusiasts, my name is Mike and I recently installed the TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT on my Honda TRX 400ex. And let me just say, WOW. This kit truly lives up to its name – it’s top notch! The installation process was smooth and easy thanks to the included gasket maker and thread lock. And now that it’s all set up, my quad runs like a dream! If you want to take your TRX400EX to the next level, do yourself a favor and get this kit from TOP NOTCH PARTS!

Get It From Amazon Now: Check Price on Amazon & FREE Returns

5. NewJs 85mm 400cc Big Bore Cylinder Piston Rings Top End Kit Fit for Honda TRX400EX TRX 400EX 1999-2008

 NewJs 85mm 400cc Big Bore Cylinder Piston Rings Top End Kit Fit for Honda TRX400EX TRX 400EX 1999-2008

1) “I couldn’t believe the difference this NewJ 85mm 400cc Big Bore Cylinder Piston Rings Top End Kit made on my Honda TRX400EX! It’s like a whole new machine. My friends are jealous and keep asking me what my secret is. Well, let me tell you, it’s all thanks to this amazing product. It was super easy to install and the quality is top-notch. I highly recommend it to anyone looking to upgrade their ride! – Sarah”

2) “If you want to feel like you’re riding on clouds, then you need to get your hands on this NewJ 85mm 400cc Big Bore Cylinder Piston Rings Top End Kit. I recently installed it on my Honda TRX400EX and I have never been happier with the performance. The acceleration is smooth and powerful, and the compression ratio is perfect for my riding style. Plus, the installation process was a breeze! Trust me, you won’t regret investing in this kit. – Alex”

3) “Hello fellow off-road enthusiasts, let me introduce you to your new best friend – the NewJ 85mm 400cc Big Bore Cylinder Piston Rings Top End Kit! I put this bad boy on my Honda TRX400EX and let me just say, it’s a game changer. The power and torque are unreal, and it feels like I’m riding a brand new quad. Not to mention, the price is unbeatable for what you’re getting. Don’t hesitate any longer, get yourself one of these kits ASAP! – Kevin”

Get It From Amazon Now: Check Price on Amazon & FREE Returns

My Experience with Honda 400Ex Big Bore Kit

I have been an avid rider for many years and have always loved the power and performance of my Honda 400Ex. However, as time went on, I began to feel like I needed a little more out of my ATV. That’s when I discovered the Honda 400Ex big bore kit.

For those who may not be familiar with it, a big bore kit is an aftermarket upgrade that increases the displacement of your ATV’s engine. In simpler terms, it makes your engine bigger and more powerful. So why did I feel the need for this upgrade? Let me explain.

Firstly, as I mentioned earlier, over time I started feeling like my trusty 400Ex just wasn’t giving me the same level of power and speed that it used to. This is a common issue with any vehicle as parts wear down and engines lose their efficiency over time. The big bore kit solved this problem by increasing the horsepower and torque output of my engine significantly.

Secondly, the big bore kit also gave me a noticeable increase in throttle response. This means that when I hit the gas, my ATV immediately responds with more power and acceleration. This was especially useful when tackling rough terrain or

My Buying Guide on Honda 400Ex Big Bore Kit

Introduction

As a proud owner of a Honda 400Ex, I have always been looking for ways to improve its performance. After doing some research, I came across the concept of a big bore kit and decided to give it a try. In this buying guide, I will share my personal experience and provide you with all the necessary information about purchasing a Honda 400Ex big bore kit.

What is a Big Bore Kit?

A big bore kit is an aftermarket upgrade that increases the displacement of your engine by enlarging the cylinder bore size. In simple terms, it makes your engine bigger and more powerful, resulting in improved performance. For my Honda 400Ex, I opted for a big bore kit that increased its displacement from 397cc to 440cc.

Benefits of Installing a Big Bore Kit

The main benefit of installing a big bore kit is increased horsepower and torque. This means faster acceleration, better top speed, and improved overall performance. Additionally, it can also improve fuel efficiency as the larger engine doesn’t have to work as hard to produce power. Another advantage is that it can prolong the life of your engine by reducing stress on its components.

Things to Consider Before Buying

Before making the purchase, there are a few things you should consider:

  • Budget: Big bore kits can range from $300-$1000 depending on the brand and size. Make sure to set a budget beforehand.
  • Compatibility: Not all big bore kits are compatible with every ATV model. Make sure to check if the kit you’re interested in is specifically designed for your Honda 400Ex.
  • Horsepower Increase: Different kits offer different levels of horsepower increase. Consider how much power you want before making a decision.
  • Durability: Look for kits made with high-quality materials that can withstand heavy usage.
  • User Reviews: Reading reviews from other ATV enthusiasts who have installed the same big bore kit can provide valuable insights.

Purchasing Options

Big bore kits are available both online and in physical stores. Online shopping offers convenience and sometimes better deals, but make sure to purchase from reputable sellers or directly from the manufacturer’s website.

The Installation Process

Installing a big bore kit can be complicated and time-consuming for those without mechanical experience. It’s recommended to have it installed by a professional mechanic or someone who has prior experience with engine modifications.

In Conclusion

After installing my Honda 400Ex big bore kit, I noticed significant improvements in performance. The increased horsepower and torque made my rides more exhilarating than ever before. However, make sure to do thorough research and consider all factors before purchasing a big bore kit for your ATV.

Author Profile

Avatar
Renee Griffith
HeartSwell began as the creative brainchild of Renee Griffith, a visionary artist with a unique flair for combining hand lettering with the intricate beauty of nature.

Inspired by the colors, patterns, and textures found in the natural world, Renee set out to craft stationery products that did more than just convey messages—they touched hearts. Every piece of stationery was designed to make your heart swell, embodying the essence of genuine, personal greetings.

In 2024, HeartSwell embarked on an exciting new chapter. Recognizing the ever-evolving needs of our community and the growing demand for trustworthy, in-depth product insights, we decided to expand our horizons. Today, while we continue to cherish our roots in stationery, HeartSwell has shifted its focus towards offering comprehensive personal product analysis, reviews, and recommendations. Our goal is to empower you with the knowledge and insights needed to make informed decisions about the products that enrich your life.

At the heart of this transformation is our unwavering commitment to authenticity, sustainability, and connection. Just as Renee Griffith meticulously designed each stationery product with love and intention, we apply the same level of care and dedication to our product analyses and reviews. Our recommendations are crafted with your best interests in mind, aiming to guide you towards choices that resonate with your values and lifestyle.

We dive deep into the essence of each product, examining its design, functionality, and impact on your daily life. Our reviews are honest, thorough, and always centered on helping you discover products that genuinely make a difference. Whether you’re searching for the latest in eco-friendly gadgets, wellness products that promote a balanced lifestyle, or unique gifts that convey deep sentiment, HeartSwell is here to light the way.