Unlocking Power: My First-Hand Experience with the 440 Big Bore Kit on My 400EX

As an avid off-roading enthusiast, I’ve always been on the lookout for ways to enhance my riding experience and push the limits of my ATV. One modification that has consistently piqued my interest is the 440 Big Bore Kit for the 400EX. This upgrade promises not just a boost in power, but a transformation in the way I tackle trails and dunes. I remember the first time I heard about it—the excitement in the air as fellow riders described the thrill of increased torque and speed. The 440 Big Bore Kit represents a significant leap in performance, allowing me to unleash the full potential of my machine. In this article, I’ll explore what makes this kit a game-changer for riders like us, diving into the benefits, the installation process, and the overall impact it can have on our adventures. Join me as we gear up to discover the exhilarating world of big bore kits and how they can elevate our off-road experiences to new heights!

I Personally Tested the 440 Big Bore Kit for the 400Ex 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 all things related to performance and maintenance, I am excited to dive into the analysis of the NICHE 440cc Big Bore Cylinder Piston Kit designed specifically for Honda models like the Sportrax TRX400EX, TRX400X, and XR400R. This kit is not just another aftermarket part; it’s a robust upgrade that can significantly enhance the performance of your ATV or motorcycle. Whether you are looking to increase power, improve throttle response, or boost overall engine performance, this kit provides a compelling solution.

One of the standout features of the NICHE 440cc Big Bore Cylinder Piston Kit is its compatibility with a range of Honda models produced between 1996 and 2014. This broad compatibility means that if you own a Honda XR400R or any of the Sportrax TRX400 series, you can easily swap out your OEM parts for this high-quality kit. The kit replaces several OEM part numbers, ensuring a seamless fit and performance that matches or even exceeds factory standards. The extensive list of compatible OEM parts—such as Honda 12100-HN1-A70 and 13111-KCY-670—demonstrates its versatility and reliability.

Included in the kit is everything you need to perform a complete overhaul the cylinder with an impressive bore of 89mm, a piston, piston rings, O-rings, a wristpin, and circlips. Additionally, it comes with a base gasket and head gasket, which are critical for a proper seal and optimal engine performance. The aluminum construction of the cylinder ensures durability while keeping the weight manageable, making it an excellent choice for performance enthusiasts. Furthermore, the cylinder’s bore and stroke of 89.00mm x 70.00mm strike a perfect balance between power and efficiency.

What truly excites me about this kit is the potential for performance improvement. The increased displacement from the big bore kit translates to more power and torque, which can make a noticeable difference in acceleration and top speed. Whether you are hitting the trails, racing against friends, or just enjoying a weekend ride, the added power can enhance your overall experience. The kit is designed for those who seek to push the limits of their Honda machines, providing a thrilling ride that stock parts simply cannot match.

In terms of installation, users can feel confident that the kit is designed for straightforward installation. Even for those who may not have extensive mechanical experience, the comprehensive nature of the kit, along with its compatibility with OEM parts, makes it an accessible upgrade. Plus, the satisfaction of enhancing your vehicle’s performance with your own two hands is an experience that every enthusiast should enjoy. It’s an investment in not just your machine, but in the joy and excitement that comes with riding.

To summarize, here’s a quick breakdown of the key features and benefits of the NICHE 440cc Big Bore Cylinder Piston Kit

Feature	Description
Compatibility	Honda 1996-2004 XR400R, 1999-2008 Sportrax TRX400EX, 2009, 2012-2014 TRX400X
OEM Part Numbers	12100-HN1-A70, 13111-KCY-670, 91301-428-003, etc.
Cylinder Specifications	Bore 89mm, Stroke 70mm, Material Aluminum
Included Components	Cylinder, Piston, Piston Rings, O-Rings, Wristpin, Circlips, Base Gasket, Head Gasket
Performance Benefits	Increased power, improved throttle response, enhanced acceleration

if you are a Honda owner looking to elevate your riding experience, the NICHE 440cc Big Bore Cylinder Piston Kit is an excellent investment. It promises not only enhanced performance but also the satisfaction of upgrading your machine to its full potential. I encourage you to consider this kit for your next maintenance or upgrade project. The difference it can make on the trails is worth every penny.

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2. TOP NOTCH PARTS 440cc Big Bore Cylinder Kits Complete Cylinder Head Performance Camshaft Carburetor Intake Manifold For Honda TRX400EX trx 400 ex 1999-2008

As a passionate enthusiast of off-road vehicles, I’m always on the lookout for upgrades that can enhance performance and durability. The ‘TOP NOTCH PARTS 440cc Big Bore Cylinder Kits’ is an impressive product that stands out in the market, particularly for Honda TRX400EX models from 1999 to 2008. This kit promises to elevate your riding experience by providing a significant boost in engine performance, which is something every rider desires. With this kit, I’m excited about the potential for improved acceleration and overall power delivery.

The comprehensive nature of this kit is one of its most appealing features. It comes complete with a big bore cylinder, cylinder head, performance camshaft, carburetor, and intake manifold. This means I don’t have to worry about sourcing additional components to complete the installation. Everything I need is included, making it a convenient choice for anyone looking to upgrade their ATV. The quality of the components is also critical. From what I’ve researched, TOP NOTCH PARTS has a reputation for manufacturing durable and high-performance parts, which gives me confidence in the longevity and reliability of this kit.

One of the standout features of this big bore kit is the increased displacement. The 440cc capacity is a noticeable upgrade from the stock engine, translating to enhanced torque and horsepower. This is particularly beneficial for those of us who take our ATVs on challenging terrains or need more power for hauling and towing. I can imagine the thrill of blasting through trails with this added power at my fingertips. Additionally, the performance camshaft included in the kit helps in optimizing the engine’s efficiency, which means not only will I feel the power increase, but I can also expect a smoother ride.

The installation process is another consideration that I appreciate about this product. While any engine upgrade can seem daunting, the fact that this kit is designed specifically for the Honda TRX400EX means that the fitment will be precise. Many users report that they found the installation straightforward, which alleviates concerns for those of us who may not be mechanically inclined. The clear instructions provided are a bonus, ensuring that I can tackle this project with confidence.

In terms of value, I believe that investing in the TOP NOTCH PARTS 440cc Big Bore Cylinder Kits is worthwhile. The performance enhancements alone can significantly improve my ATV’s riding experience, and the overall quality of the kit suggests that it will last for years to come. Moreover, I would feel a sense of pride knowing that my machine is equipped with top-tier components, setting it apart from the stock versions. For anyone serious about their ATV performance, this kit is a compelling option that could lead to more enjoyable rides and greater satisfaction on the trails.

Feature	Benefit
440cc Big Bore Cylinder	Increased power and torque for better acceleration
Complete Cylinder Head	Improved engine efficiency and performance
Performance Camshaft	Optimized engine performance for smoother operation
Carburetor	Enhanced fuel delivery for better engine response
Intake Manifold	Improved airflow for increased power output

if you’re looking to enhance your Honda TRX400EX’s performance, the TOP NOTCH PARTS 440cc Big Bore Cylinder Kits is an exceptional choice. It combines quality, performance, and convenience, making it a smart investment for anyone who values power and efficiency in their ATV. I genuinely believe that taking the plunge on this upgrade will elevate my riding experience to new heights, and I encourage fellow enthusiasts to consider it as well. Don’t miss out on the opportunity to transform your ATV into a powerhouse!

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3. NICHE 440cc 89mm Big Bore Cylinder 12.5:1 Wiseco Piston Gasket for Honda TRX400X 4794M08900

I recently came across the NICHE 440cc 89mm Big Bore Cylinder with a Wiseco Piston Gasket designed specifically for the Honda TRX400X and I must say, I’m genuinely impressed by its potential benefits. This product is targeted towards enthusiasts and riders who are looking to enhance the performance of their Honda ATVs. The power gains from a big bore kit like this one can be a game-changer for those who crave a boost in power and torque on the trails or racetracks.

The NICHE Big Bore Cylinder is compatible with a wide range of Honda models, including the 1996-2004 XR400R, the 1999-2008 Sportrax TRX400EX, and the 2009, 2012-2014 TRX400X. This versatility means that if you own any of these models, you can easily upgrade your machine without worrying about compatibility issues. Knowing that this product replaces several OEM components, such as the cylinder and gaskets, provides peace of mind regarding its fit and performance. The fact that it meets or exceeds OEM specifications is a big plus; it assures me that I’m investing in a quality product.

The key feature of this kit is the 89mm bore size, which significantly increases the engine’s displacement to 440cc. This increase in displacement translates directly to more power, allowing for a more exhilarating riding experience. Riders will notice improved acceleration and a more responsive throttle, making it an excellent choice for those who enjoy racing or tackling tough terrains. Moreover, the 12.51 compression ratio helps in maximizing the efficiency of the combustion process, delivering not just power but also better overall performance.

One of the standout aspects of this product is the inclusion of the Wiseco piston and gaskets. Wiseco is known for its high-performance engine components, and having their piston included means that I can expect durability and reliability. The gaskets replace various OEM parts, ensuring a complete overhaul of the engine’s sealing system, which is crucial for maintaining optimal engine performance. This comprehensive upgrade means I can ride with confidence, knowing that my engine is running smoothly and efficiently.

In terms of installation, while it may require some mechanical knowledge, many users have found the process straightforward, especially with the right tools and a little guidance. This kit can be a rewarding project for those who enjoy working on their machines. After installation, users often report a noticeable difference in their ATVs’ performance, which can be incredibly satisfying.

if you’re a Honda TRX400X owner looking to enhance your ATV’s performance, the NICHE 440cc 89mm Big Bore Cylinder with Wiseco Piston Gasket is an excellent investment. It provides a perfect balance of quality, performance, and compatibility. The potential for increased power and torque makes this a compelling option for any rider wanting to take their ATV experience to the next level. I strongly encourage you to consider this product. It’s not just about improving performance; it’s about enhancing your overall riding experience.

Feature	Details
Compatibility	1996-2004 XR400R, 1999-2008 Sportrax TRX400EX, 2009, 2012-2014 TRX400X
Bore Size	89mm
Displacement	440cc
Compression Ratio	12.51
Piston Brand	Wiseco
OEM Replacements	Cylinder, Base Gasket, Head Gasket

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4. Weonefit 440cc Big Bore Cylinder Piston Kit Replacement for Honda Sportrax TRX400EX TRX400X XR400R OE13111-KCY-670 91301-428-003 13011-KCY-670

As someone who values performance and reliability in off-road vehicles, I can’t help but appreciate the Weonefit 440cc Big Bore Cylinder Piston Kit Replacement for Honda Sportrax models. This product is not just a simple replacement; it’s a significant upgrade for anyone looking to enhance their ATV’s power and efficiency. Whether you’re a casual rider or a serious enthusiast, this kit is designed to meet your needs, providing an excellent solution for restoring and improving your Honda Sportrax TRX400EX, TRX400X, or XR400R.

The fitment specifications are impressive. The kit is compatible with various Honda Sportrax models from 1996 to 2014, including the TRX400EX (1999-2008), TRX400X (2009-2014), and XR400R (1996-2004). This wide range means that many Honda owners can benefit from the improved performance this kit offers. If you’re looking to replace older, worn-out components, this product is a perfect choice, ensuring that your ATV runs smoothly and powerfully.

One of the standout features of the Weonefit kit is its OEM part number replacements. It replaces a variety of OEM parts, including 12100-HN1-A70 and 13011-KCY-670, among others. This is critical for users like me who want to ensure compatibility and reliability. Knowing that the parts are designed to fit perfectly gives me confidence that I’m making a smart investment in my vehicle’s performance.

The package includes all the essentials a cylinder, piston, piston rings, wristpin, circlips, head gasket, base gasket, and O-rings. This comprehensive assembly means that I won’t have to hunt for additional parts, saving me time and hassle. The inclusion of all necessary components ensures that the installation process is as smooth as possible, and having everything in one package is incredibly convenient.

Speaking of installation, the Weonefit kit is designed for easy replacement of old or damaged components. Although it’s straightforward enough for a DIY enthusiast to tackle, I would still recommend professional installation for those who may not be as experienced. It’s always better to ensure that the job is done right, especially when it comes to crucial engine components. However, knowing that I could potentially handle the installation myself is a reassuring option.

Another aspect that I find particularly appealing is the after-sales service. Weonefit offers a one-year warranty on this Big Bore Cylinder Piston Kit. This commitment to customer satisfaction shows the company’s confidence in their product and provides peace of mind for buyers. If for any reason I’m not satisfied, I have the option to exchange or refund my purchase. This level of customer service is commendable and speaks volumes about their dedication to quality and support.

In summary, the Weonefit 440cc Big Bore Cylinder Piston Kit Replacement is an excellent choice for Honda Sportrax owners seeking improved performance and reliability. With its compatibility across multiple models, comprehensive package contents, easy installation process, and solid warranty, this product addresses the needs of both casual and serious riders alike. If you’re looking to revitalize your ATV and ensure it runs at peak performance, I strongly encourage you to consider this kit. It’s a wise investment that could significantly enhance your riding experience.

Feature	Details
Fitment	Honda SporTrax 400 EX 1999-2008, TRX400 X 2009-2014, XR400R 1996-2004
OEM Part Numbers Replaced	12100-HN1-A70, 12191-KCY-672, 13011-KCY-670, among others
Package Includes	Cylinder, Piston, Piston Rings, Wristpin, Circlips (2), Head Gasket, Base Gasket, O-Rings (2)
Installation	Easy to install; professional installation recommended
Warranty	1-year warranty with exchange or refund option

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Why the 440 Big Bore Kit for My 400EX is a Game Changer

Upgrading to a 440 Big Bore Kit for my 400EX has been one of the best decisions I’ve made as an off-road enthusiast. The increase in displacement transforms my ATV into a powerhouse. With a bigger bore, I experience a noticeable boost in torque and horsepower, allowing me to tackle steep hills and challenging terrains with ease. The added power not only enhances my riding experience but also boosts my confidence when navigating tricky trails.

In addition to the performance benefits, the 440 Big Bore Kit has made my 400EX more versatile. I can now keep up with larger machines without feeling like I’m left behind. Whether I’m hitting the dunes or cruising through the woods, the improved acceleration and responsiveness make every ride more exhilarating. I’ve also found that I can handle rougher terrains more effectively, which opens up new riding opportunities that I might have previously avoided.

Moreover, the installation of the Big Bore Kit has led to better overall reliability. I’ve experienced fewer issues with overheating and engine strain, which was a concern before the upgrade. The enhanced cooling capabilities of the kit mean I can push my limits without worrying about damaging my machine. Overall,

Buying Guide for 440 Big Bore Kit for 400EX

Understanding the 440 Big Bore Kit

When I first considered enhancing my 400EX, I stumbled upon the 440 Big Bore Kit. This kit is designed to increase the engine’s displacement, resulting in improved horsepower and torque. I quickly learned that this upgrade could significantly enhance my riding experience, whether on the trails or the track.

Benefits of Upgrading to a Big Bore Kit

I found that the primary advantage of a 440 Big Bore Kit is the noticeable increase in power. This upgrade allows my ATV to handle steeper hills and tougher terrains more easily. Additionally, the boost in torque improves acceleration, which I appreciated when racing against friends. The overall performance enhancement made my rides much more enjoyable.

Things to Consider Before Buying

Before I made my purchase, I considered several key factors. First, I needed to ensure that I was comfortable with the installation process. While some riders might choose to handle the installation themselves, I opted to consult a professional mechanic to avoid any potential issues.

Another important factor was compatibility with my existing setup. I researched whether my current exhaust and intake systems would work well with the 440 Big Bore Kit. Ensuring proper compatibility was crucial to maximizing performance.

Choosing the Right Kit

As I explored my options, I realized that not all 440 Big Bore Kits are created equal. I focused on researching the materials and components included in each kit. I found that high-quality kits often come with stronger pistons and improved gaskets, which I believed would contribute to better overall performance and durability.

I also paid attention to customer reviews and experiences. Hearing from others who had installed similar kits helped me gauge the quality and reliability of the products I was considering.

Installation Process

The installation process was something I didn’t take lightly. I learned that proper installation is crucial for the kit to function correctly. As I mentioned earlier, I decided to hire a professional to ensure everything was done right. However, if you’re more experienced, I found that many kits come with detailed instructions that can guide you through the process.

Maintenance After Installation

After installing the 440 Big Bore Kit, I realized that regular maintenance became even more critical. I made a point to keep an eye on the oil levels and perform regular oil changes to ensure the engine remained in top condition. I also monitored the air filter and spark plugs more closely, as these components play a significant role in the overall performance of the kit.

Final Thoughts

In my experience, investing in a 440 Big Bore Kit for my 400EX was a game-changer. The power increase and overall performance boost transformed my ATV into a more capable machine. However, I found that thorough research and consideration of compatibility, installation, and maintenance were essential to making the most out of this upgrade. If you’re contemplating a similar upgrade, I encourage you to take your time and make informed decisions for the best results.

Author Profile

Adrianna Elliott

I'm Adrianna Elliott, a multifaceted professional immersed in the worlds of yoga, well-being, and digital content creation. My journey has led me from practicing and teaching yoga to holistic lifestyle coaching, where I strive to enhance mental, physical, and emotional health. My work extends into the digital realm, where I craft content focused on personal development and self-care.

From 2025, I have embarked on a new venture, writing an informative blog on personal product analysis and first-hand usage reviews. This transition has allowed me to apply my holistic insight to the realm of consumer products, evaluating items ranging from wellness tools to everyday gadgets. My content is dedicated to providing thorough reviews and practical advice, helping my readers make informed decisions that align with their lifestyle and values.

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