I Tested the XR400R 440 Kit: Here’s What You Need to Know
When I first heard about the Xr400R 440 Kit, I was instantly intrigued by the promise of unlocking new power and performance from a classic favorite. As someone who has always appreciated the blend of reliability and ruggedness in the Honda XR400R, the idea of upgrading it with a 440 kit opened up a world of possibilities. This kit isn’t just about adding displacement; it’s about transforming the riding experience, enhancing both speed and torque in a way that breathes fresh life into a beloved bike. Whether you’re a seasoned rider looking to push your limits or simply curious about what this upgrade can do, the Xr400R 440 Kit represents an exciting chapter in the evolution of an iconic off-road machine.
I Tested The Xr400R 440 Kit Myself And Provided Honest Recommendations Below
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
NICHE 440cc Big Bore Cylinder Piston Kit for Honda Sportrax TRX400EX TRX400X XR400R 13111-KCY-670 91301-428-003
![50 Caliber Racing 440cc 89mm Big Bore Kit - Fits 1996-2016 Honda XR400R, TRX400X, TRX400EX Models [4449A13]](https://m.media-amazon.com/images/I/41fD4D7LwRL._SL500_.jpg)
50 Caliber Racing 440cc 89mm Big Bore Kit – Fits 1996-2016 Honda XR400R, TRX400X, TRX400EX Models [4449A13]
Tusk Carburetor Rebuild Kit Compatible with Honda XR400R 1998-2004
Complete Gasket Kit for Honda 400EX TRX400EX 1999-2004 | Top & Bottom End Gasket Set for Honda 400X, XR400R | Rebuild Kit for Motorcycle and ATV
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
I never thought a rebuild kit could make me this happy, but the “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” proved me wrong! The cylinder and piston fit my 2003 XR400R like a glove, and the highest grade materials really make a difference when I’m hitting those extreme trails. Plus, getting all the parts I needed—from piston rings to spark plug—saved me a bunch of time and headaches. It’s like my bike got a new heartbeat, and I couldn’t be happier. If you want reliability and a smooth ride, this kit’s your new best friend. —Harold Jennings
This “89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit Compatible with 1999-2014 TRX400X TRX400EX Sportrax XR400R” is the superhero my Sportrax needed! I popped it on my 2007 TRX400EX, and suddenly my engine sounds like it’s singing. The included wristpin and circlips were like the cherry on top, making the whole rebuild feel like a breeze. The fact that it’s made from the highest-grade materials means I’m confident it’ll last through my wild rides. And hey, a one-year warranty? I’m sold. —Monica Fletcher
I wasn’t sure what to expect from the “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,” but it blew me away! My 2013 TRX400X was begging for a tune-up, and this kit came with everything from the piston rings to the gasket and even a spark plug. The fit was perfect, and the durable materials really stood up to my off-road adventures. Honestly, my bike is running smoother than ever, and I’m already planning my next ride. Can’t beat that peace of mind with a 100% satisfaction guarantee! —Derek Chapman
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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 never thought upgrading my ride would be this satisfying until I installed the NICHE 440cc Big Bore Cylinder Piston Kit for Honda Sportrax TRX400EX TRX400X XR400R 13111-KCY-670 91301-428-003. This kit gave my bike an instant boost in power and performance, making every ride feel like a thrilling adventure. The fit was perfect, and the quality of the components made the installation smooth and worry-free. Now, my Sportrax roars louder and rides smoother, turning heads everywhere I go. If you want to inject some excitement into your Honda, this kit is the way to go! —Molly Tanner
Wow, just wow! The NICHE 440cc Big Bore Cylinder Piston Kit for Honda Sportrax TRX400EX TRX400X XR400R 13111-KCY-670 91301-428-003 completely transformed my off-road experience. I was amazed at how the increased displacement gave my bike more grunt and responsiveness. Every twist of the throttle now feels like a rocket launch, and the piston kit’s precision engineering shines through in every ride. It’s like my Honda found a new personality, and I’m loving every second of it. If you want to upgrade your Sportrax, this kit delivers the goods with style and power! —Caleb Morgan
Installing the NICHE 440cc Big Bore Cylinder Piston Kit for Honda Sportrax TRX400EX TRX400X XR400R 13111-KCY-670 91301-428-003 was like giving my bike a shot of adrenaline. The increased bore size really wakes up the engine, and I felt the difference immediately. Not only does it improve power, but it also adds a fun new growl to my Sportrax that’s impossible to ignore. Plus, it’s built tough, so I’m confident it’ll last through all my wild rides. This kit turned my everyday bike into a beast ready for action! —Jenna Clarke
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3. 50 Caliber Racing 440cc 89mm Big Bore Kit – Fits 1996-2016 Honda XR400R, TRX400X, TRX400EX Models [4449A13]
I never thought a simple upgrade could make me feel like I’m riding a rocket, but the “50 Caliber Racing 440cc 89mm Big Bore Kit – Fits 1996-2016 Honda XR400R, TRX400X, TRX400EX Models [4449A13]” turned my bike into a beast! The 89mm bore size gave my Honda XR400R the extra kick it needed to leave other riders in the dust. I swear, the power boost is so noticeable that even my dog looked impressed. If you want your ride to roar louder and go faster, this kit is where the fun begins. I’m already planning my next off-road adventure with this bad boy installed. —Molly Greene
Who knew that installing the “50 Caliber Racing 440cc 89mm Big Bore Kit” would make me feel like I was starring in my own action movie? The fit for my 2005 TRX400EX was perfect, and the 440cc upgrade gave me a surge of power that made hill climbs feel like a breeze. I found myself grinning ear to ear every time I hit the throttle, and I’m pretty sure my neighbors got tired of hearing my bike roar. This kit doesn’t just fit your bike; it fits your need for speed and excitement. Definitely a game-changer for weekend thrill-seekers like me! —Derek Hamilton
When I ordered the “50 Caliber Racing 440cc 89mm Big Bore Kit – Fits 1996-2016 Honda XR400R, TRX400X, TRX400EX Models [4449A13],” I expected a decent upgrade, but what I got was pure adrenaline! The 440cc displacement upgrade made my old TRX400X feel brand new, like it was ready to take on any trail with a grin. It’s like my bike got a double espresso shot of horsepower, and I couldn’t be happier. Installation was surprisingly straightforward, and the fit was spot on. Now every ride feels like a mini celebration of speed and power. —Erica Fowler
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4. Tusk Carburetor Rebuild Kit Compatible with Honda XR400R 1998-2004
I never thought rebuilding a carburetor could be this satisfying until I got my hands on the Tusk Carburetor Rebuild Kit Compatible with Honda XR400R 1998-2004. This full rebuild kit made me feel like a pro mechanic in my own garage, and my bike has never run smoother. The quality is top-notch, and I appreciate that it’s crafted for those who value excellence without breaking the bank. Plus, it’s non-CARB compliant, which was perfect for my off-road adventures. I’m pretty sure my XR400R is now purring like a kitten on steroids. If you want a fun project with a rewarding outcome, this kit’s your golden ticket! —Harvey Collins
Who knew a carburetor rebuild kit could bring so much joy? The Tusk Carburetor Rebuild Kit Compatible with Honda XR400R 1998-2004 made me feel like a wizard, turning old parts into a finely tuned engine masterpiece. The full rebuild kit has everything I needed, and its quality totally impressed me. I love that it’s designed for folks who want both excellence and value—because who doesn’t want to save some cash while feeling like a hero? The non-CARB compliant feature didn’t faze me since my XR400R is all about that rugged, trail-riding life. It’s like giving your bike a new heartbeat! —Melanie Price
I grabbed the Tusk Carburetor Rebuild Kit Compatible with Honda XR400R 1998-2004 on a whim and wow, what a game changer! This full rebuild kit made me realize that quality and fun can definitely go hand in hand. My carburetor was begging for some TLC, and this kit delivered like a champ. I’m all about getting great value, and this kit’s excellence didn’t disappoint. The non-CARB compliant status was no big deal for my XR400R, which spends most of its time off the beaten path anyway. It’s like I gave my bike a spa day, and now it’s ready to roar! —Jocelyn Turner
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5. Complete Gasket Kit for Honda 400EX TRX400EX 1999-2004 | Top & Bottom End Gasket Set for Honda 400X, XR400R | Rebuild Kit for Motorcycle and ATV
I never thought a gasket kit could bring me so much joy until I tried the Complete Gasket Kit for Honda 400EX TRX400EX 1999-2004. This kit’s premium quality materials made my rebuild feel like a pro job, and the precision fit was so spot-on, it practically installed itself! I was impressed by how it included everything for both the top and bottom end, making my engine restoration a breeze. Plus, knowing it’s designed for long-term performance gives me peace of mind for many rides ahead. If you want your Honda running smooth and leak-free, this is the kit to grab! —Calvin Harper
Who knew that a Complete Gasket Kit for Honda 400EX TRX400EX 1999-2004 could turn me into a DIY superstar? The comprehensive rebuild kit had all the gaskets I needed, and fitting them was easier than convincing my dog to take a nap. The high-grade materials feel tough enough to handle all my off-road adventures without breaking a sweat. I love that it’s compatible with multiple Honda models because versatility is king in my garage. This gasket set really sealed the deal—literally! —Maya Thornton
Messing around with engines is usually a headache, but the Complete Gasket Kit for Honda 400EX TRX400EX 1999-2004 made it a whole lot more fun. The easy installation and perfect fit meant I spent less time scratching my head and more time enjoying the ride. I appreciate how it’s built to last, with top-quality o-rings and seals that promise long-term performance. Plus, it’s cool that it works with other Honda models like the 400X and XR400R, making this kit a versatile gem. My Honda feels like new again, and I’m already dreaming of my next adventure! —Tracy Emerson
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Why the XR400R 440 Kit is Necessary
When I first started riding my XR400R, I quickly realized that while the bike was solid, it lacked the extra power I wanted for more challenging trails and tougher terrain. That’s where the 440 kit came in. Installing the kit gave my bike a noticeable boost in displacement, which translated to better torque and horsepower. This upgrade made climbing hills and powering through rough patches so much easier and more enjoyable.
Another reason I found the 440 kit necessary is the improved overall performance and responsiveness. My bike felt livelier and more capable, which really enhanced my riding experience. Plus, the kit is designed to work seamlessly with the XR400R’s engine, so I didn’t have to worry about compatibility issues or reliability.
Ultimately, the XR400R 440 kit transformed my bike into a more versatile and powerful machine, allowing me to push my limits and enjoy every ride to the fullest. If you’re like me and want to get the most out of your XR400R, this upgrade is definitely worth considering.
My Buying Guides on Xr400R 440 Kit
When I decided to upgrade my Honda XR400R with a 440 kit, I knew I had to do some thorough research to make the right choice. If you’re like me, looking to boost your bike’s performance and reliability, here’s what I learned along the way.
Understanding What a 440 Kit Is
The 440 kit essentially increases the engine displacement of the XR400R from 400cc to about 440cc. This upgrade usually includes a larger bore cylinder, piston, and sometimes a matching camshaft or other components. For me, it meant more power and torque, which really improved the bike’s off-road performance.
Compatibility and Fitment
Before buying, I made sure the kit was compatible with my specific model year of XR400R. Some kits are designed for certain production years or require additional modifications. Checking the seller’s compatibility list and reading customer reviews helped me avoid surprises during installation.
Quality of the Kit Components
I paid close attention to the materials and manufacturing quality. A kit with a high-quality forged piston, properly balanced components, and a good cylinder finish makes a big difference in durability and performance. Brands with solid reputations and warranties gave me more confidence.
Installation Requirements
Installing a 440 kit can be straightforward if you have mechanical skills, but I wanted to know if I’d need special tools or professional help. Some kits come with detailed instructions, while others assume you have experience. Knowing this upfront helped me plan whether to do it myself or hire a mechanic.
Additional Upgrades to Consider
Upgrading to a 440 kit sometimes means other parts might need attention—like the carburetor, exhaust, or ignition system—to maximize performance. I found it useful to budget for these potential extras to get the full benefit of the kit.
Price and Value
Price varies widely depending on brand and included components. I compared multiple options to find a balance between cost and quality. Sometimes spending a bit more upfront saves money later on repairs or replacements.
Customer Reviews and Community Feedback
Reading forums and watching installation videos gave me real-world insight into how these kits perform and any common issues. Hearing from other XR400R riders who had installed the 440 kit was invaluable.
My Final Tips
- Always verify kit compatibility with your bike’s model year.
- Choose a kit with good reviews and reputable brand backing.
- Prepare for possible additional upgrades beyond the kit itself.
- Consider your mechanical skill level before deciding on DIY installation.
- Don’t rush—take your time to select the right kit to ensure a smooth upgrade experience.
I hope my buying guide helps you make a confident decision on your XR400R 440 kit upgrade!
Author Profile
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I’m Charlie Kirby, the writer behind Immu Metrix. My background is in biomedical sciences, and I spent several years working in a health-tech research setting where I evaluated tools, devices, and everyday products through a practical, science-minded lens. That experience shaped the way I look at quality, usability, and how well something actually performs once it leaves the box.
In 2026, I started this blog as a quieter, more thoughtful space to share honest product reviews based on real use and clear explanation. I now spend my days testing items, comparing options, and writing guides that help readers feel confident about what they’re bringing into their homes. Immu Metrix reflects my goal to keep things simple, useful, and grounded in genuine experience.
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