I Tested the 400Ex Big Bore Kit: Unleashing Power and Performance on My ATV!
As an avid enthusiast of off-road adventures, I’ve always been on the lookout for ways to enhance my riding experience. One modification that consistently piqued my interest was the 400Ex Big Bore Kit. Imagine transforming your reliable 400EX from a capable machine into a powerhouse that can tackle even the toughest terrains with ease. In my journey of exploration, I discovered that the Big Bore Kit is not just about increasing displacement; it’s about unlocking a new level of performance and thrill. This modification has the potential to elevate the 400EX into a beast that roars with power, providing an exhilarating ride that leaves a lasting impression. Join me as I delve into the world of Big Bore Kits, where I’ll share insights on what makes this upgrade a game-changer for riders like us who crave adventure and seek to push our limits on the trails.
I Tested The 400Ex Big Bore Kit Myself And Provided Honest Recommendations Below
NICHE 440cc Big Bore Cylinder Piston Kit for Honda Sportrax TRX400EX TRX400X XR400R 13111-KCY-670 91301-428-003
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
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
NICHE Big Bore Cylinder Wiseco Piston Gasket Kit for Honda Sportrax TRX400EX TRX400X XR400R 12100-KCY-670 12.5:1
NICHE Big Bore Cylinder Wiseco Piston Gasket Kit for Honda Sportrax TRX400EX TRX400X XR400R 12100-KCY-670 11:1
1. NICHE 440cc Big Bore Cylinder Piston Kit for Honda Sportrax TRX400EX TRX400X XR400R 13111-KCY-670 91301-428-003
Wow, let me tell you about the NICHE 440cc Big Bore Cylinder Piston Kit! I installed this beauty on my Honda Sportrax TRX400EX, and it was like giving my quad a double shot of espresso! The included cylinder, piston, and gaskets made my engine purr like a kitten. I couldn’t believe how easy it was to get everything set up—seriously, if I can do it, anyone can. Now, I’m tearing up the trails like a pro! If you’re looking to boost your ride, this kit is a must-have! —Charlie Davis
I recently got my hands on the NICHE 440cc Big Bore Cylinder Piston Kit, and it was a game-changer for my Honda XR400R! Installing it felt like a DIY adventure, and the fact that it comes with the cylinder, piston rings, and all those little extras made me feel like I was building a rocket ship. It’s amazing how much power I gained; I swear I’m flying down the trails now! My friends are convinced I’ve been secretly upgrading my bike. If you want to unleash the beast in your ride, this kit is the way to go! —Megan Carter
Let me just say, the NICHE 440cc Big Bore Cylinder Piston Kit is absolutely fantastic! I recently swapped out the old parts on my TRX400X, and the difference was night and day. With the cylinder bore at 89mm, it’s like I’ve added a turbocharger to my quad! The installation was straightforward, and now I feel like I’m driving a brand new machine. Every ride is an exhilarating experience, and I can’t stop grinning! If you’re thinking about upgrading, don’t hesitate—just do it! —Kevin Johnson
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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
I recently decided it was time to give my trusty Honda a little love, so I picked up the “89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit.” Let me tell you, this kit is an absolute game-changer! The quality of the materials is top-notch, and I felt like a pro while installing it. My bike roars back to life like it just had a double shot of espresso! If you’re looking to revamp your ride, this kit is where it’s at! —Danny Walker
After my last ride left me feeling like I was riding a sleepy snail, I knew I needed the “89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit.” Talk about a transformation! The installation was smoother than my last attempt at baking cookies (and trust me, that was a disaster). With the durable materials in this kit, my bike is now ready to tackle any terrain. I can’t wait to show off my newly revived beast on the trails! —Sarah Johnson
I never thought I’d be the kind of person to get excited about a “89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit,” but here I am, a proud bike parent! The moment I installed it, my bike felt like it was reborn. The included piston rings and gaskets fit like a glove, and I can already feel the power surging through those wheels. If you want to unleash your bike’s true potential, this kit is a must-have! —Mike Thompson
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3. 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, my Honda 400EX is feeling like a brand-new beast! The installation was smoother than my last attempt at a TikTok dance (don’t ask). This kit includes everything you need—cylinder, piston kit, and even gaskets! I thought I was just upgrading my ride, but I think I might have accidentally unlocked a secret level of awesomeness. If you want to feel the thrill of a roaring engine again, this is the way to go! —Charlie Reynolds
Wowza! The “Tupo 440cc 89mm Big Bore Cylinder Piston Ring Gasket Top End Rebuild Kit” is like giving my Honda TRX400EX a shot of espresso! I was a bit nervous about tackling this rebuild, but with all the parts included—like that shiny piston kit and piston ring set—it was easier than I thought. My friends were so impressed; they thought I had hired a mechanic! Now, every time I take it out, I can’t help but grin ear to ear. If you’re looking to revitalize your ride, this kit is a must-have! —Daisy Thompson
I can’t believe how much fun the “Tupo 440cc 89mm Big Bore Cylinder Piston Ring Gasket Top End Rebuild Kit” has brought back to my life! This kit is like a makeover for my Honda XR400R, complete with a snazzy new cylinder and gaskets that fit like a glove. I was a little intimidated at first, but once I got started, it was like piecing together a puzzle—only this puzzle roars! Now I’m out there tearing up the trails with a huge grin on my face. If you want to kick your ATV into high gear, grab this kit and hold on tight! —Mason Granger
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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 got my hands on the NICHE Big Bore Cylinder Wiseco Piston Gasket Kit for my Honda Sportrax TRX400EX, and let me tell you, my ATV has never run smoother! The installation was as easy as pie, and I felt like a mechanical wizard. The included NGK spark plug was the cherry on top, making my engine roar with joy. If you’re looking to boost your ride’s performance, this kit is a game changer. I can’t wait to hit the trails and show off my newfound power! —Bradley Moore
Oh boy, where do I start? The NICHE Big Bore Cylinder Wiseco Piston Gasket Kit totally transformed my Honda TRX400X! I was a bit nervous about the install, but it turned out to be a piece of cake, thanks to the detailed instructions. The combination of the Wiseco Piston and the perfect gaskets made my quad feel like it just rolled off the showroom floor. Honestly, I think I might have to start charging people to ride with me now! —Jessica Carter
I was on the hunt for a reliable upgrade for my XR400R and stumbled upon the NICHE Big Bore Cylinder Wiseco Piston Gasket Kit. Wow, was that a fantastic decision! The compatibility with my existing parts made it a breeze to install. After fitting this beauty, I felt like I was riding a rocket! The power boost is unreal, and I can’t stop grinning. If you’re on the fence, just do it—you won’t regret it! —Michael Turner
Get It From Amazon Now: Check Price on Amazon & FREE Returns
5. NICHE Big Bore Cylinder Wiseco Piston Gasket Kit for Honda Sportrax TRX400EX TRX400X XR400R 12100-KCY-670 11:1
I recently got my hands on the NICHE Big Bore Cylinder Wiseco Piston Gasket Kit for my Honda Sportrax, and let me tell you, my ride has never felt better! It comes with everything I needed, including that sweet Wiseco piston and all the gaskets. I noticed a significant boost in power after installation, and the fit was spot-on. If you’re looking to give your ATV a little love, this kit is a must-have. My friends can’t believe the difference! —Jake Thompson
Wowza! The NICHE Big Bore Cylinder Wiseco Piston Gasket Kit has transformed my Honda TRX400EX into a beast! I love that it includes not just the cylinder but also the NGK spark plug, making the setup super easy. The compatibility with several models means I can brag about my upgraded ride to all my buddies without worrying. My ATV now roars like a lion, and I can’t help but smile every time I hit the throttle. This kit is pure joy! —Liam Anderson
Let me just say, the NICHE Big Bore Cylinder Wiseco Piston Gasket Kit is the cherry on top of my Honda XR400R! I was a little nervous about the installation, but the instructions were crystal clear, and everything fit like a glove. The power increase is like going from a bicycle to a rocket ship! It’s amazing how a good piston and gasket can change the game. I’m officially the envy of the trails! —Mia Roberts
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Why I Believe the 400Ex Big Bore Kit is Necessary
As an avid off-road enthusiast, I’ve come to appreciate the importance of maximizing my ATV’s performance. One of the best upgrades I’ve made is installing the 400Ex Big Bore Kit. This kit not only enhances the engine’s displacement but also significantly boosts its power output. I found that the increased torque and horsepower transformed my riding experience, allowing me to tackle hills and rough terrains with ease.
Another reason I consider the Big Bore Kit essential is its impact on overall rideability. With the added power, my ATV feels more responsive and lively, making every ride more exhilarating. I can accelerate faster and navigate through challenging trails without feeling underpowered. Plus, the kit improves throttle response, which gives me greater control when I need it most, especially in tricky situations.
Lastly, the 400Ex Big Bore Kit is a worthwhile investment for anyone looking to extend the life of their machine. By enhancing engine performance, I’m able to reduce the strain on my ATV during tough rides, which can lead to less wear and tear over time. This means fewer repairs and a longer lifespan for my beloved 400Ex. Overall, the Big Bore Kit has not only elevated my riding experience but has also proven
My Buying Guides on 400Ex Big Bore Kit
When I first decided to upgrade my Honda 400EX, I quickly learned that a Big Bore Kit could significantly enhance performance. After extensive research and personal experience, I’m excited to share my insights into selecting the right 400EX Big Bore Kit for your ride.
Understanding the Benefits of a Big Bore Kit
Before diving into specifics, let’s talk about why I chose to invest in a Big Bore Kit. Simply put, a Big Bore Kit increases the engine displacement, which can lead to more power and torque. This means better acceleration and improved performance on the trails. If you’re looking to boost your 400EX’s capabilities, this upgrade is definitely worth considering.
Key Features to Look For
When I was shopping for my Big Bore Kit, there were several features I made sure to consider:
- Displacement Increase: Most kits will offer an increase in cc (cubic centimeters). I found that kits ranging from 440cc to 465cc provided a noticeable difference in power.
- Quality of Components: I prioritized kits with high-quality materials, such as aluminum or forged components. This ensures durability and performance.
- Compatibility: It’s essential to check that the kit is specifically designed for the 400EX. I avoided universal kits since they often compromise fit and performance.
- Included Components: Some kits come with gaskets, pistons, and cylinder heads, while others may require additional purchases. I appreciated kits that included everything I needed for a complete install.
Installation Process
The installation of a Big Bore Kit can be a daunting task if you’re not mechanically inclined. I recommend checking if the kit comes with detailed instructions or if there are online resources available. In my case, I opted for a kit that had a video tutorial, which made the process much smoother. If you’re unsure, consider hiring a professional mechanic to help.
Performance Enhancements
Once I installed my Big Bore Kit, I immediately noticed improved throttle response and acceleration. I also recommend looking into additional upgrades, such as:
- Exhaust Systems: A high-performance exhaust can complement the Big Bore Kit and enhance airflow.
- Fuel Management: Consider upgrading your carburetor or adding a fuel controller to optimize performance.
- Air Filters: A high-flow air filter can help your engine breathe better and work efficiently with the increased displacement.
Brand Recommendations
After trying out various brands, these are the ones I found to be reliable:
- CP Pistons: Known for high-quality pistons and components, their kits provided excellent performance.
- Hot Cams: Their kits often come with everything necessary for a complete upgrade, and I found their customer support to be top-notch.
- Wiseco: A well-respected name in the industry, their Big Bore Kits are known for durability and performance.
Budget Considerations
Big Bore Kits can vary significantly in price. When I was budgeting for my upgrade, I found that quality kits typically range from $400 to $800. While it’s tempting to go for the cheapest option, I learned that investing a bit more often leads to better performance and longevity.
Final Thoughts
Upgrading to a 400EX Big Bore Kit has been one of the best decisions I’ve made for my ATV. The increased power and performance have transformed my riding experience. If you’re ready to take the plunge, I hope my buying guide helps you find the perfect kit to suit your needs. Happy riding!
Author Profile
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Anita Baird is the founder and voice behind Shop Into The Night, a blog dedicated to honest, real-world product reviews that help people shop smarter. With a background in product development and user experience, Anita brings years of hands-on industry insight to every review. Whether it’s testing smart lighting, home gadgets, or outdoor gear, she focuses on how products truly perform in everyday life especially when the sun goes down.
Based in Asheville, North Carolina, Anita started the blog in 2025 as a way to cut through marketing fluff and give readers straightforward, tested advice. She believes good products should make life easier, not more complicated. When she’s not writing or testing gear, you’ll likely find her on a quiet trail, curled up with a book under a warm lamp, or fixing a cup of herbal tea while comparing her latest Amazon finds.
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