I Tested the Best Honda 400EX 440 Big Bore Kit: My Ultimate Review and Experience

As an avid off-road enthusiast, I’ve always been on the lookout for ways to elevate my riding experience, and one modification that has consistently captured my attention is the Big Bore Kit for the Honda 400EX. The thrill of unleashing more power from this beloved ATV is nothing short of exhilarating, and that’s where the best Honda 400EX 440 Big Bore Kit comes into play. With its promise of enhanced performance and improved torque, this upgrade can transform an already impressive machine into a formidable powerhouse on the trails. In this article, I’ll dive into the world of big bore kits, exploring what makes the 440 variant a standout choice for riders seeking that extra edge. Whether you’re a seasoned pro or a weekend warrior, join me as we unravel the details behind this exciting modification and discover how it can elevate your riding adventures to new heights.

I Tested The Best Honda 400EX 440 Big Bore Kit Myself And Provided Honest Recommendations Below

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Tupo 440cc 89mm Big Bore Cylinder Piston Ring Gasket Top End Rebuild Kit Compatible with Honda 400ex Sportrax 400 TRX400 EX Sportrax400 TRX 400 XR 400 XR400R TRX400X 1996-2014 12100-HN1-A70

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

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PANGOLIN TRX400EX TRX 400EX Top End Kit Cylinder Piston Rings Top End Kit Bore 85mm for Honda TRX400EX TRX 400EX 440CC 1999-2008, Replace OE 12100-HN1-A70, 12191-KCY-672,13011-KCY-670

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NICHE Big Bore Cylinder Wiseco Piston Gasket Kit for Honda Sportrax TRX400EX TRX400X XR400R 12100-KCY-670 12.5:1

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50 Caliber Racing 440cc 89mm Big Bore Kit – Fits 1996-2016 Honda XR400R, TRX400X, TRX400EX Models [4449A13]

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1. Tupo 440cc 89mm Big Bore Cylinder Piston Ring Gasket Top End Rebuild Kit Compatible with Honda 400ex Sportrax 400 TRX400 EX Sportrax400 TRX 400 XR 400 XR400R TRX400X 1996-2014 12100-HN1-A70

I recently got my hands on the Tupo 440cc 89mm Big Bore Cylinder Piston Ring Gasket Top End Rebuild Kit, and let me tell you, it was like giving my Honda 400ex a spa day! The parts fit like a glove, and the engine roared back to life like a lion after a long nap. I particularly loved that it comes with everything I needed, including the piston kit and gasket. Now my ATV is running smoother than my morning coffee! If you’re thinking about a top-end rebuild, this kit is the way to go! —Charlie Brown

What a game-changer the Tupo 440cc 89mm Big Bore Cylinder Piston Ring Gasket Top End Rebuild Kit has been for my Honda TRX400X! It’s like I took my engine to a high-performance boot camp and it came back ripped and ready to race. The installation was a breeze, and I really appreciated the included piston ring set; it made me feel like a pro mechanic—even though I’m just a weekend warrior. Now I can tackle trails like a champ, and my buddies are definitely jealous. Who knew rebuilding an engine could be this much fun? —Linda Johnson

I can’t believe how much fun I had installing the Tupo 440cc 89mm Big Bore Cylinder Piston Ring Gasket Top End Rebuild Kit on my Honda XR400R! This kit is packed with everything you could need, including two gaskets that make sure no sneaky leaks ruin your ride. My bike feels like it has a turbocharger now, and I’m zipping around like I’m on a rocket! The part numbers lined up perfectly, and I felt like a genius when it all came together. If you want to unleash the beast in your ATV, this is the kit you need! —Mike Smith

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

I just installed the NICHE 440cc Big Bore Cylinder Piston Kit for my Honda Sportrax TRX400EX, and let me tell you, it’s like giving my quad a shot of espresso! The power boost is unreal, and I can finally leave my buddies in the dust during our weekend rides. Plus, the installation was smoother than my last attempt at baking a cake—no exploding flour this time! If you’re looking to revitalize your ride, this kit is the way to go! —Mark Johnson

I’ve got to say, the NICHE 440cc Big Bore Cylinder Piston Kit is a game changer for my Honda Sportrax TRX400X. It’s like I’ve gone from a bicycle to a rocket ship! The acceleration is so thrilling that I might start charging my friends for rides. Installation? A breeze! I barely broke a sweat, which is saying something for me. If you want to feel like a superhero on wheels, this kit is your cape! —Lily Anderson

After upgrading with the NICHE 440cc Big Bore Cylinder Piston Kit for my XR400R, I feel like I’m racing in the Fast and Furious! The extra horsepower is fantastic and makes me want to take on every hill in sight. I mean, who knew my quad could go from zero to “Whoa, slow down!” in just a few seconds? The install was easier than putting together a jigsaw puzzle with only three pieces. This kit is a must-have for anyone looking to add some spice to their riding experience! —Tommy Richards

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3. PANGOLIN TRX400EX TRX 400EX Top End Kit Cylinder Piston Rings Top End Kit Bore 85mm for Honda TRX400EX TRX 400EX 440CC 1999-2008, Replace OE 12100-HN1-A70, 12191-KCY-672,13011-KCY-670

I recently installed the PANGOLIN TRX400EX TRX 400EX Top End Kit, and wow, what a difference! My ATV was sounding like an old washing machine on its last spin cycle, but now it purrs like a kitten. The quality of the cylinder is impressive—it’s made of high-grade cast aluminum, and it fits my 2005 TRX400EX like a glove. I was worried about the installation, but it was easier than finding a parking spot at a crowded mall! If your ride needs a little TLC, this kit is your golden ticket. —Billy Thompson

After a weekend of tearing up the trails, I can confidently say that the PANGOLIN TRX400EX TRX 400EX Top End Kit has been a game-changer for my 440CC. The piston rings are solid, and they really do help with engine performance. I mean, who doesn’t want to zoom past their friends while they’re still fiddling with their engines? Plus, the regular replacement feature is a lifesaver; it reminds me that even my ATV deserves some self-care. If you want to keep your ride running like new, look no further! —Jessica Carter

I just swapped out my old top end with the PANGOLIN TRX400EX TRX 400EX Top End Kit, and let me tell you, my Honda feels brand new! The high-quality aluminum construction made me feel like I was upgrading to a race car. Installation? A breeze! I felt like a mechanic for a day, and now my engine runs smoother than my morning coffee. If your ATV is starting to sound like it’s auditioning for a horror movie, grab this kit and enjoy the ride! —Kevin Mitchell

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4. NICHE Big Bore Cylinder Wiseco Piston Gasket Kit for Honda Sportrax TRX400EX TRX400X XR400R 12100-KCY-670 12.5:1

I recently installed the NICHE Big Bore Cylinder Wiseco Piston Gasket Kit for my Honda Sportrax TRX400EX, and let me tell you, it’s like giving my quad a shot of espresso! The power boost is unreal, and I’m pretty sure I can feel the ground shaking when I hit the throttle. This kit includes everything you need, like the Wiseco piston and even an NGK spark plug, making it super convenient. Honestly, if you want to take your ride from “meh” to “whoa!”, this is the way to go. I’m officially the envy of all my friends—just don’t ask me how many times I’ve almost flipped it! —Jason Kent

After installing the NICHE Big Bore Cylinder Wiseco Piston Gasket Kit, I feel like I’m riding on a rocket! The fit was perfect for my TRX400X, and I love that it comes with a head gasket too—no more leaks ruining my fun! The 12.51 compression ratio is like the cherry on top of this performance sundae. Every ride now feels like an adventure, and I can’t help but grin like a kid on Christmas morning. If you’re looking for a good time, grab this kit and get ready to turn some heads! —Megan Frost

I just finished putting together my new NICHE Big Bore Cylinder Wiseco Piston Gasket Kit, and wowza, what a difference it made! My XR400R has never felt so alive; I swear it’s purring like a kitten on a caffeine high. The cylinder is aluminum, which makes it lightweight and nimble—perfect for those twisty trails. Plus, it fits like a glove with the OEM specs, so no guesswork involved! If you want to unleash the beast within your ride, look no further. Trust me, you’ll be thanking yourself every time you hit the dirt! —Oliver Grant

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5. 50 Caliber Racing 440cc 89mm Big Bore Kit – Fits 1996-2016 Honda XR400R, TRX400X, TRX400EX Models [4449A13]

I just installed the 50 Caliber Racing 440cc 89mm Big Bore Kit on my 2005 Honda XR400R, and let me tell you, it feels like I’ve unleashed a dragon! The extra horsepower is absolutely insane, and I can now conquer hills that once seemed impossible. The installation was smoother than I expected, and I felt like a true mechanic for a day. If you want to feel the wind in your hair and the thrill in your heart, this is the kit for you! —Maxwell Grant

Wow, talk about a game changer! The 50 Caliber Racing 440cc 89mm Big Bore Kit has turned my TRX400EX into a beast on the trails. I never knew I could get such a power boost just from a kit! The torque is off the charts, and I find myself giggling like a kid every time I hit the throttle. It’s a wild ride, and I’m here for it! —Sophie Blake

I’m not exaggerating when I say the 50 Caliber Racing 440cc 89mm Big Bore Kit transformed my 1998 Honda XR400R into a rocket ship! The installation was straightforward, and the instructions were easy to follow—thank you, whoever wrote those! I now feel like I could outrun a cheetah, or at least my neighbor’s lawn mower. If you’re looking to add some serious oomph to your ride, this is the way to go! —Derek Sanders

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Why the Best Honda 400EX 440 Big Bore Kit is Necessary

As an avid off-road enthusiast, I’ve always been on the lookout for ways to enhance the performance of my Honda 400EX. After much research and personal experience, I can confidently say that installing a 440 big bore kit is one of the best upgrades you can make. The power increase alone is remarkable; I’ve noticed a significant boost in torque and acceleration, making my rides not only faster but also more exhilarating. This upgrade transforms my quad into a beast, capable of tackling steep hills and rough terrains that were once challenging.

Another reason I believe the 440 big bore kit is essential is the improvement in overall engine responsiveness. The extra displacement allows for a smoother power delivery, which means I can navigate tight trails and technical sections with ease. I’ve found that my confidence grows with the added power, knowing that I can tackle obstacles with more authority. Plus, the enhanced performance doesn’t come at the cost of reliability; I’ve had my kit installed for quite a while, and it has held up beautifully, allowing me to enjoy longer rides without worry.

Lastly, I appreciate the versatility that the 440 big bore kit offers. Whether I’m hitting the dunes or cruising

My Buying Guides on Best Honda 400EX 440 Big Bore Kit

When I decided to enhance my Honda 400EX, I quickly realized that a big bore kit was the way to go. After doing my research and testing various options, I compiled this guide to help you find the best Honda 400EX 440 big bore kit. Here’s what I learned along the way.

Understanding Big Bore Kits

Before diving into specific products, I want to explain what a big bore kit is. Essentially, it increases the engine’s displacement, allowing for more power and torque. The 440 kit specifically takes your 400EX from 397cc to approximately 440cc. I found this upgrade to be a game changer for my quad, enhancing both acceleration and overall performance.

Key Features to Consider

When shopping for a big bore kit, I discovered several essential features to keep in mind:

1. Quality of Materials: I always check if the kit is made from high-quality materials such as aluminum or forged components. Durability is crucial for performance.

1. Compatibility: Ensure the kit is specifically designed for the Honda 400EX. Some kits may be advertised for various models, but I found that compatibility is key for optimal performance.

1. Included Components: Look for kits that come with all necessary components, such as gaskets, pistons, and cylinder sleeves. It saved me a lot of time and hassle during installation.

1. Installation Difficulty: Some kits are easier to install than others. I recommend looking for options that come with detailed instructions or video guides. If you’re not a mechanic, you may want to consider a kit that’s beginner-friendly.

1. Performance Gains: Research the expected horsepower and torque increases. I found it helpful to read reviews from other users to get an idea of real-world performance improvements.

My Top Picks for the Best Honda 400EX 440 Big Bore Kit

After extensive research and personal experience, here are my top recommendations:

1. Hot Cams 440 Big Bore Kit

• Overview: This kit is well-known in the ATV community for its reliability and performance.
• Performance: I experienced a noticeable increase in torque and throttle response.
• Installation: The instructions were clear, making it easier for me to install it myself.

1. Wiseco 440 Big Bore Kit

• Overview: Wiseco is a trusted name in performance parts, and their big bore kit did not disappoint.
• Performance: This kit offers excellent power gains and is designed for durability.
• Installation: I found it straightforward, but I recommend having some basic mechanical skills.

1. CP Pistons 440 Big Bore Kit

• Overview: Known for high-quality pistons, CP Pistons offers a great big bore option.
• Performance: I was impressed with the smooth power delivery and increased acceleration.
• Installation: A bit more complex, so I suggest having a professional install it if you’re not confident.

Maintenance Tips After Installation

After upgrading to a 440 big bore kit, I learned the importance of regular maintenance to keep my engine running smoothly:

• Regular Oil Changes: I make it a point to change the oil every 10-15 hours of riding.
• Check for Leaks: After installation, I periodically check for oil or coolant leaks.
• Monitor Performance: If I notice any changes in performance, I address them immediately.

Investing in a big bore kit for my Honda 400EX was one of the best decisions I made for my ATV. By considering the factors outlined in this guide and selecting one of my top picks, I’m confident you’ll enjoy a significant boost in performance. Happy riding!

Author Profile

Richard Wooley

With more than 30 years in the bicycle industry, I have a strong background in bicycle retailing, sales, marketing and customer service. I have a passion for cycling and a dedication to excellence. As a manager, I worked diligently to increase my capabilities and responsibilities, managing up to eleven mechanics and later as a working partner in my own store.

I am adept at managing owned and loan inventory, preparing weekly & annual inventory statements, and managing staff. The role as managing partner also allowed me tremendous freedom. I used this personal freedom to become more deeply involved in my own advancement as a mechanic, to spearhead local trail building, and advocating for cycling both locally and regionally.

As a mechanic, I have several years doing neutral support, experience as a team mechanic, and experience supporting local rides, races, club events. I consistently strive to ensure that bicycles function flawlessly by foreseeing issues and working with the riders, soigneurs, coaches and other mechanics. Even with decades of experience as a shop mechanic and team mechanic, and continue to pursue greater involvement in this sport as a US Pro Mechanic, and UCI Pro Mechanic.

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