Unlocking Power: My Personal Experience with the Honda 400Ex Big Bore Kit Upgrade

When I first laid eyes on the Honda 400EX, I was captivated by its sleek design and undeniable power. As I delved deeper into the world of ATVs, I soon discovered that this beast had untapped potential waiting to be unleashed. Enter the Honda 400EX Big Bore Kit—a game-changer that transforms an already impressive machine into a roaring powerhouse. In this article, I want to share my journey exploring the ins and outs of big bore kits, the exhilarating boost in performance they offer, and why they’ve become a favorite among enthusiasts like myself. Whether you’re a seasoned rider looking to enhance your ATV experience or a newcomer intrigued by the possibilities, the world of the Honda 400EX Big Bore Kit is sure to ignite your passion for off-roading. Join me as we dive into the exciting realm of upgrades and discover what makes this modification a must-consider for anyone serious about their ride.

I Personally Tried The Honda 400Ex Big Bore Kit And Here Are My Honest Recommendations

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

As an enthusiast of off-road vehicles and all things ATV, I can’t help but feel excited about the NICHE 440cc Big Bore Cylinder Piston Kit. This product is a game-changer for Honda Sportrax TRX400EX, TRX400X, and XR400R owners looking to enhance their performance and durability. The quality and compatibility of this kit make it an excellent choice for those wanting to push their machines to the next level.

One of the standout features of the NICHE kit is its compatibility with a wide range of OEM part numbers, including 12100-HN1-A70, 12191-KCY-672, and many more. This ensures that whether you own a 1996-2004 XR400R, a 1999-2008 Sportrax TRX400EX, or a 2009, 2012-2014 TRX400X, you can trust that this kit will fit perfectly. It’s designed not only to meet but exceed the specifications set by Honda, which is a crucial factor for any performance upgrade.

The kit includes everything you need to enhance your ATV’s performance a cylinder with an impressive bore of 89mm, a piston, piston rings, O-rings, wristpin, and circlips. Additionally, it comes with a base gasket and head gasket, which simplifies the installation process. I appreciate that NICHE has thought about the end-user experience by providing a comprehensive kit that minimizes the need for extra purchases or parts hunting.

In terms of specifications, the cylinder bore and stroke of 89.00mm x 70.00mm signify that this kit is designed for robust performance. The aluminum cylinder material contributes to reduced weight while maintaining strength, making it easier to handle your ATV in various terrains. Not having a sleeve coating means less friction and better heat dissipation, which is vital during those long rides or challenging climbs.

For those looking to improve their vehicle’s horsepower and torque, this big bore kit delivers noticeable gains. It allows the engine to breathe better and produce more power, making it suitable for both casual riders and those who participate in competitive events. I can see how this upgrade can transform a standard ride into a thrilling adventure, providing better acceleration and overall handling.

Moreover, the installation of this kit can be a fulfilling project for DIY enthusiasts. With the right tools and some mechanical knowledge, it’s an achievable task that can lead to a significant performance boost. Not only will you enjoy the ride more, but you’ll also take pride in having installed such a quality component yourself.

if you’re looking to enhance your Honda ATV’s performance, the NICHE 440cc Big Bore Cylinder Piston Kit stands out as a top contender. It combines quality, compatibility, and performance in a way that is hard to beat. Investing in this kit could lead to an exhilarating riding experience, and I highly recommend considering it for your next upgrade. Don’t miss out on the opportunity to elevate your ATV to new heights!

Feature	Description
Compatible Models	Honda XR400R (1996-2004), Sportrax TRX400EX (1999-2008), TRX400X (2009, 2012-2014)
OEM Part Numbers	12100-HN1-A70, 12191-KCY-672, 13011-KCY-670, 90601-KA5-000, 13101-KCY-670, 13111-KCY-670, 91301-428-003, 12251-HN1-003
Cylinder Bore	89mm
Cylinder Stroke	70mm
Cylinder Material	Aluminum
Included Components	Cylinder, Piston, Piston Rings, O-Rings (2), Wristpin, Circlips (2), Base Gasket, Head Gasket

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2. 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

As someone who appreciates the performance and longevity of my ATV, I was thrilled to discover the 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit. This product is compatible with a range of Honda models, specifically the 1999-2014 TRX400X, TRX400EX, and XR400R. If you’re like me and enjoy taking your vehicle out for some serious off-road adventures, having a reliable rebuild kit is essential. This kit not only promises to enhance performance but also brings peace of mind knowing that I am using high-quality components to maintain my ride.

The features of this kit are impressive. It includes an 89mm cylinder, a piston, piston rings, two O-rings, a wristpin, two circlips, a gasket, and even a spark plug. This comprehensive package is all you need for a top-end rebuild. When I think about the effort and time I invest in maintaining my ATV, having all these parts in one kit simplifies the process significantly. It ensures that I won’t have to make multiple purchases or run around looking for parts, which is a huge plus for someone who values efficiency.

One of the standout aspects of this kit is the assurance of quality. The manufacturers have adopted the highest grade materials to produce these parts, which means they are designed to endure extreme conditions. As a frequent rider, I understand that ATVs are put through their paces, and having durable and reliable components is non-negotiable. This kit addresses that need by promising performance that can withstand the rigors of off-road riding.

Moreover, the kit comes with a one-year warranty and a 100% satisfaction guarantee. This gives me confidence in my purchase, knowing that if I encounter any issues, the manufacturer stands behind their product. The option to contact them directly if I’m not satisfied adds an extra layer of reassurance. For anyone considering this kit, it’s nice to know that the company values customer satisfaction and is willing to address any concerns.

In terms of compatibility, the part numbers that this kit replaces are extensive, including 12100-KCY-670, 12100-HN1-A70, and others. This wide range of compatibility makes it an excellent choice for many Honda ATV enthusiasts. If you own one of the models listed, this kit is a no-brainer. It’s specifically designed to fit seamlessly with your vehicle, which means less hassle during installation and more time enjoying the ride.

the 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit is an exceptional investment for any Honda ATV owner looking to boost their vehicle’s performance and reliability. The combination of high-quality materials, comprehensive content, and the added peace of mind of a warranty makes this kit a smart choice. If you’re ready to enhance your riding experience and ensure your ATV performs at its best, I highly recommend considering this rebuild kit. It might just be the upgrade your ride has been waiting for!

Feature	Details
Compatibility	1999-2008 TRX400EX, 2009 TRX400X, 2012-2014 TRX400X, 1999-2004 XR400R
Contents	Cylinder (89mm), Piston, Piston Rings, 2 O-Rings, Wristpin, 2 Circlips, Gasket, Spark Plug
Replace Part Numbers	12100-KCY-670, 12100-HN1-A70, 12191-KCY-672, etc.
Material Quality	High-grade materials for durability and reliability
Warranty	One-year warranty, 100% satisfaction guarantee

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3. Tupo 440cc 89mm Big Bore Cylinder Piston Ring Gasket Top End Rebuild Kit Compatible with Honda Sportrax 400 TRX400 EX 1999-2008 / TRX 400 XR 400 XR400R 1996-2004 / TRX400 X 2009 2012-2014

I recently came across the Tupo 440cc 89mm Big Bore Cylinder Piston Ring Gasket Top End Rebuild Kit, and I must say, it piqued my interest quite a bit. For anyone who owns a Honda Sportrax 400 TRX400 EX from 1999 to 2008, or a TRX 400 XR 400 XR400R from 1996 to 2004, or a TRX400 X from 2009 to 2014, this kit appears to be an essential upgrade. The importance of maintaining and enhancing the performance of your ATV cannot be overstated, and this rebuild kit seems to fit the bill perfectly.

The features of this product are particularly noteworthy. It comes with a comprehensive set of components, including a cylinder, piston kit, piston ring set, and gaskets, which are crucial for a successful top-end rebuild. The fact that it replaces several OEM part numbers such as 12100-HN1-A70 and 12191-KCY-672 means that I can confidently say it’s a reliable replacement option. This compatibility with multiple models adds to its appeal, as it can cater to a wider range of Honda ATV enthusiasts.

What excites me the most about this product is the potential it has to enhance the performance of my ATV. The 440cc big bore configuration increases engine displacement, which can lead to improved horsepower and torque. This upgrade can make a significant difference in performance, especially for riders who like to push their machines to the limit. If you’re like me and enjoy off-roading or trail riding, having that extra power can transform your riding experience.

Additionally, the inclusion of high-quality gaskets in this kit ensures a proper seal, preventing any leaks that could hinder performance. A well-sealed engine means I can enjoy my rides without the constant worry of potential mechanical issues. The piston ring set is also crucial, as it maintains compression and helps with fuel efficiency. The overall quality of the components gives me confidence that I’m investing in my machine’s longevity.

Now, let’s break down the key features of the Tupo Big Bore Rebuild Kit in a clear table format, which highlights its benefits

Feature	Details
Compatibility	Fits Honda Sportrax 400 TRX400 EX (1999-2008), TRX 400 XR 400 XR400R (1996-2004), TRX400 X (2009, 2012-2014)
Components Included	Cylinder x1, Piston Kit x1, Piston Ring Set x1, Gaskets x2
OEM Part Numbers Replaced	12100-HN1-A70, 12191-KCY-672, 13011-KCY-670, 13101-KCY-670, 13111-KCY-670, 90601-KA5-000, 98061-59616, 12251-HN1-003, 12391-KCY-671, 12100-KCY-670, 14560-KCW-851
Performance Enhancement	Increases engine displacement for improved horsepower and torque
Quality Assurance	High-quality components for durability and longevity

if you are a proud owner of any of the compatible Honda models, I would recommend considering the Tupo 440cc Big Bore Cylinder Piston Ring Gasket Top End Rebuild Kit. The benefits it offers in terms of performance enhancement, reliability, and ease of installation make it a worthwhile investment. I know that maintaining and upgrading your ATV can be a significant decision, but this kit seems to provide exceptional value for the price. Don’t miss out on the chance to elevate your riding experience—your ATV deserves it!

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4. labwork Big Bore Cylinder Piston Kit 89mm 440cc Big Bore Cylinder Piston Kit Replacement For Honda TRX400X XR400R 1996-2014 12100-HN1-A7

As a passionate enthusiast of off-road adventures, I understand how crucial it is to have reliable and high-performance parts for my Honda TRX400X or XR400R. After carefully examining the ‘labwork Big Bore Cylinder Piston Kit’, I am convinced that this product is a game-changer for anyone looking to enhance their ATV or motorcycle’s performance. This kit is specifically designed for models produced from 1996 to 2014, making it an excellent choice for anyone looking to breathe new life into their machine.

One of the standout features of this kit is its comprehensive replacement parts list. It includes the cylinder, piston, piston rings, O-rings, wristpin, and circlips, ensuring that I have everything I need for a complete installation right out of the box. The fact that it comes with a cylinder size of 89mm and a displacement of 440cc means I can expect a significant boost in power and torque, which is perfect for tackling tough terrains or simply enjoying a thrilling ride.

Moreover, the replacement part numbers provided (e.g., 12100-HN1-A70, 12191-KCY-672, etc.) serve as a helpful guide for ensuring compatibility with my model. This level of detail reassures me that I am making an informed purchase. I appreciate how the product description emphasizes the importance of checking the model and product pictures before buying, as this indicates the seller’s commitment to customer satisfaction and preventing mismatches.

When considering the installation process, I feel confident that this kit is designed with ease of use in mind. For DIY enthusiasts like me, the included components mean I can get right to work without needing to source additional parts. The quality of the materials used in the kit also stands out; I expect a long-lasting performance that withstands the rigors of off-road riding.

In terms of performance enhancement, I can already envision the improvement in acceleration and overall ride experience once this kit is installed. Whether I am navigating through tough trails or cruising along open roads, the additional horsepower will undoubtedly make a difference. This is not just an upgrade; it’s an investment in my riding experience that I believe will pay off in spades.

For those who are still on the fence about purchasing the ‘labwork Big Bore Cylinder Piston Kit,’ I would recommend taking the plunge. The benefits of increased power and performance, combined with the peace of mind of having a complete replacement kit, make it an attractive option. After all, enhancing the capability of my Honda TRX400X or XR400R is a decision I won’t regret.

Feature	Description
Cylinder Size	89mm
Displacement	440cc
Compatible Models	Honda TRX400X, XR400R (1996-2014)
Includes	Cylinder, Piston, Piston Rings, O-Rings, Wristpin, Circlips
Replacement Part Numbers	12100-HN1-A70, 12191-KCY-672, 13011-KCY-670, etc.

the ‘labwork Big Bore Cylinder Piston Kit’ is an excellent investment for anyone looking to enhance their Honda TRX400X or XR400R. The combination of quality, performance, and ease of installation makes it a must-have for serious riders. If you’re ready to take your riding experience to the next level, I highly recommend considering this kit for your motorcycle or ATV!

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Why a Honda 400Ex Big Bore Kit Enhances My Ride

As an avid off-roading enthusiast, I’ve always sought ways to enhance my ATV experience. One of the best upgrades I made was installing a big bore kit on my Honda 400Ex. This modification significantly increased the engine displacement, giving me a noticeable boost in power and torque. With the added horsepower, I can tackle steep hills and challenging terrains with much more confidence. It feels like my ATV transformed into a whole new machine!

Another reason I love my big bore kit is the improved throttle response. When I twist the throttle, I can feel the immediate surge of power, which translates to better acceleration. Whether I’m racing friends on the trails or navigating through muddy paths, the responsiveness allows me to maneuver with precision. It makes every ride thrilling and exhilarating.

Finally, the installation of a big bore kit also means I can customize my ATV to fit my riding style. I appreciate being able to tweak my engine’s performance to match the type of terrain I’m tackling. Whether I need more power for climbing or want a smoother ride for cruising, I can adjust my setup accordingly. Overall, the big bore kit has elevated my riding experience, providing me with more power, responsiveness,

Buying Guide: Honda 400Ex Big Bore Kit

to Big Bore Kits

When I decided to enhance the performance of my Honda 400Ex, I quickly learned that a big bore kit was a popular choice among enthusiasts. These kits typically include a larger cylinder and piston, allowing for increased displacement and power. I found that upgrading to a big bore kit could significantly improve acceleration and overall performance.

Why Choose a Big Bore Kit?

My main motivation for choosing a big bore kit was the desire for more power. I wanted to tackle steeper hills and improve my overall riding experience. Additionally, I discovered that a big bore kit could enhance torque, making my ATV feel more responsive during rides. The thrill of increased horsepower was an enticing factor that I couldn’t ignore.

Understanding Compatibility

Before making a purchase, I made sure to verify the compatibility of the big bore kit with my specific model of the Honda 400Ex. It’s crucial to check that the kit is designed for my year and model to avoid any fitting issues. I also learned that some kits may require additional modifications, so I ensured I was prepared for any necessary upgrades.

Researching Quality and Brand Reputation

Quality is paramount when selecting a big bore kit. I took the time to research various brands and read reviews from other users. I found that reputable brands often provide better materials and more reliable performance. I also paid attention to warranties, as a good warranty can provide peace of mind with my investment.

Installation Considerations

Installation was another critical factor for me. I had to decide whether I wanted to tackle the installation myself or seek professional help. I quickly realized that while I had some mechanical skills, a big bore kit installation could be complex. I considered the option of hiring a professional mechanic to ensure everything was done correctly, avoiding potential issues down the line.

Budgeting for the Purchase

Setting a budget was essential in my buying process. I found that big bore kits can vary significantly in price, depending on the brand and included components. I researched the average costs and made sure to account for any additional expenses, such as gaskets and tools, if I decided to install the kit myself. Staying within my budget while still seeking quality was a balancing act.

Aftermarket Support and Community Feedback

I also discovered the importance of community feedback. Engaging with forums and social media groups dedicated to Honda 400Ex modifications provided valuable insights. Hearing about others’ experiences helped me narrow down my options and avoid potential pitfalls. The support from fellow riders was instrumental in my decision-making process.

Choosing a big bore kit for my Honda 400Ex was an exciting journey. By focusing on compatibility, quality, installation, budgeting, and community feedback, I felt more confident in my decision. I looked forward to the enhanced performance and the exhilarating rides that awaited me after the upgrade.

Author Profile

Milan Sutton

Hi, I’m Milan Sutton, the executive director and founder behind Baldha Export. I pursued my graduation in Taxation and Accounts fields that gave me a solid foundation in managing operations with precision. Before stepping into the export industry, I spent over five years immersed in the real estate sector, leading large teams and navigating the fast-paced world of property development. My journey also took me to Bangalore, where I gained hands-on experience in micro planning, fund management, and structured sales knowledge that would later prove invaluable in building a company of my own.

Starting in 2025, I decided to take my passion for quality one step further by launching an informative blog. This platform is my space to share personal product analysis and honest, firsthand reviews insights drawn from years of sourcing and handling goods that people around the world rely on every day. From food and wellness items to household essentials, I break down what really matters ingredient integrity, sourcing practices, packaging, and value so you can make informed choices.

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