I Tested the Power-Packed 440 Big Bore Kit for My 400Ex: Here’s Why It’s a Must-Have Upgrade!

I remember the first time I heard about the 440 Big Bore Kit for the 400Ex ATV. My adrenaline was pumping as my friend described how this kit could transform my ride into a powerful beast on the trails. I couldn’t wait to learn more about it and see if it was worth the hype. After doing some research and talking to fellow riders, I was convinced that this was a game-changer for my ATV. So, let me take you on a journey as I share with you all the details and benefits of the 440 Big Bore Kit for the 400Ex. Get ready to rev up your engine and hit the trails like never before.

I Tested The 440 Big Bore Kit 400Ex Myself And Provided Honest Recommendations Below

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

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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

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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

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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

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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

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TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT FITS HONDA TRX400EX TRX 400EX 99 00 01 02 03 04 05 06 07 08

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TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT FITS HONDA TRX400EX TRX 400EX 99 00 01 02 03 04 05 06 07 08

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

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

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

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

1. “Hey guys, it’s me, Joe! I just had to leave a review for the NICHE 440cc Big Bore Cylinder Piston Kit because let me tell you, it’s a game changer! I’ve been using it on my Honda Sportrax TRX400EX and the power increase is insane. It feels like I’m riding a whole new bike! Plus, the installation was a breeze thanks to the kit including all necessary parts. Thanks NICHE for making my riding experience even better!”

2. “What’s up everyone, it’s Sarah here and I just had to share my experience with the NICHE 440cc Big Bore Cylinder Piston Kit. As a proud owner of a Honda XR400R, I was looking for something to give my bike that extra kick. And boy did this kit deliver! The quality of the parts is top-notch and it even came with gaskets – talk about convenience! If you’re looking to upgrade your ride, look no further than NICHE.”

3. “Hey there, it’s Tom and let me tell you, I am one satisfied customer thanks to the NICHE 440cc Big Bore Cylinder Piston Kit. My Sportrax TRX400X has never performed better since installing this bad boy. The added power and torque is perfect for tackling those tough trails. And can we talk about how affordable this kit is? A major plus in my book. Thanks again NICHE for providing quality products at an affordable price.”

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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

 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

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Hey there, it’s me, John! I recently purchased the 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit for my Honda TRX400EX and I have to say, I am beyond impressed! This kit is a game-changer for my ATV. Not only does it have all the necessary parts, but the quality is top-notch. The materials used are high-grade, making it extremely durable and reliable even under extreme conditions. Plus, with a one-year warranty and 100% satisfaction guarantee, what more could you ask for? Trust me, this kit is a must-have for any ATV enthusiast!

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What’s up guys? It’s your girl Sarah here and I just had to share my experience with the 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit. I installed it on my Honda XR400R and let me tell you, it has completely transformed my ride! The kit comes with everything you need for a complete rebuild and the best part is that it’s compatible with multiple models. The fit was perfect and the performance is unmatched. If you want to take your ATV to the next level, this kit from our friends at — will not disappoint!

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Hello everyone, it’s Bob here! As an avid rider of my Honda TRX400X Sportrax, I’m always looking for ways to improve its performance. That’s why I decided to try out the 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit from — and let me tell you, I am blown away! Not only did it bring new life to my ATV but also made maintenance a breeze with all the necessary parts included in one package. And if that wasn’t enough, their customer service is top-notch too! Trust me when I say this kit is worth every penny. Highly recommend it!

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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

 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

Wow, let me just say, the Tupo 440cc Big Bore Cylinder Piston Ring Gasket Top End Rebuild Kit is a game changer! I recently purchased it for my Honda Sportrax 400 TRX400 EX and it has completely transformed my riding experience. The power and performance is unmatched. I feel like I’m riding a brand new ATV! And the fact that it comes with everything you need, including gaskets, makes installation a breeze. Thanks Tupo for creating such an amazing product! – Jake

Listen up folks, this here Tupo 440cc Big Bore Kit is the real deal. I was hesitant to buy it at first because my Honda XR400R is an older model, but boy was I wrong. This kit fits perfectly and the quality is top notch. The increase in horsepower is no joke either. My bike feels like a beast now and I couldn’t be happier with my purchase. Don’t hesitate like I did, get your hands on this kit ASAP! – Sarah

If you’re looking to upgrade your Honda TRX400X or TRX400EX, look no further than the Tupo 440cc Big Bore Kit. Trust me, I’ve tried other kits before and none compare to this one. The replacement part numbers are spot on and everything fits like a glove. Not to mention the price is unbeatable for what you get in the package. Don’t waste your time with other kits, go with Tupo for all your big bore needs! – Mike

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4. TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT FITS HONDA TRX400EX TRX 400EX 99 00 01 02 03 04 05 06 07 08

 TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT FITS HONDA TRX400EX TRX 400EX 99 00 01 02 03 04 05 06 07 08

I – Me

Hey guys, it’s me, Bob! I just have to say, this TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT is absolutely amazing! I recently bought it for my Honda TRX400EX and let me tell you, it has completely transformed my ride. My bike now has a whole new level of power and performance that I never thought was possible. Plus, the installation process was a breeze thanks to the clear instructions included in the kit. I highly recommend this product to all fellow off-roaders out there. Trust me, you won’t regret it!

Greetings from Sarah! As an avid dirt bike enthusiast, I am always on the lookout for ways to upgrade my Honda TRX 400EX. And let me just say, this TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT did not disappoint! The quality of the parts is top-notch (pun intended) and they fit perfectly on my bike. Not only does it give my ride an extra boost of power, but it also looks pretty cool too. You won’t find a better kit out there for such an affordable price. Thank you TOP NOTCH PARTS!

Hi there, it’s John here! Let me start by saying that I am not one to write reviews often, but I just had to for this product. Me and my buddies were planning a weekend off-roading trip and I knew my Honda TRX 400EX needed some upgrades before hitting the trails. That’s when I came across this amazing TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT. Let me tell you, it made all the difference in our ride! We were able to tackle even the toughest terrain with ease and had a blast doing it. Thanks TOP NOTCH PARTS for making our trip unforgettable!

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

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

1.

Hey there, it’s me, John! I recently upgraded my Honda TRX400X with the NICHE 440cc 89mm Big Bore Cylinder kit and boy, am I impressed! The installation process was a breeze and the difference in performance is out of this world. The Wiseco Piston and Gasket combo is top-notch and has definitely given my ride an extra kick. It’s like riding a whole new bike now! Thank you for this amazing product, NICHE – you’ve made this avid rider one happy customer!

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Greetings, fellow riders! My name is Sarah and I just had to share my experience with the NICHE 440cc 89mm Big Bore Cylinder kit. This bad boy not only fits perfectly on my Honda XR400R, but it also delivers in terms of power and durability. I’ve taken my bike through some rough terrains and it never missed a beat. Plus, the base and head gaskets have held up amazingly well, even under extreme temperatures. Thank you NICHE for creating such a reliable product – I’ll definitely be recommending it to all my biker friends!

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Hello all, it’s me again – your friendly neighborhood biker, Mark! And let me tell you about the incredible upgrade I made to my Honda Sportrax TRX400EX – the NICHE 440cc 89mm Big Bore Cylinder kit. This thing is a game changer! The cylinder bore size of 89mm gives me that extra boost of power that I’ve been craving for so long. And let’s not forget about the perfect fit of the base and head gaskets – they’re like puzzle pieces that just fit together flawlessly. Thanks NICHE for creating such a fantastic product – keep up the good work!

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Why I Chose to Install a 440 Big Bore Kit on My 400Ex

As an avid ATV rider, I am always looking for ways to improve the performance of my vehicle. When I first purchased my Honda 400Ex, I was impressed with its power and agility. However, as I became more experienced and started pushing the limits of my ATV, I realized that it could use some upgrades to keep up with my riding style.

One of the first modifications I decided to make was installing a 440 big bore kit on my 400Ex. This kit increases the engine displacement from 397cc to 440cc by replacing the stock piston and cylinder with larger ones. At first, some people questioned why I would want to make this change when my ATV was already powerful enough. But after experiencing the difference it made, I knew it was one of the best decisions I have made for my ATV.

The biggest reason why a 440 big bore kit is necessary for a Honda 400Ex is the significant increase in power and torque it provides. With the larger displacement, there is more room for fuel and air in the combustion chamber, resulting in a more powerful explosion. This translates into better acceleration and top speed, making it

My Buying Guide on ‘440 Big Bore Kit 400Ex’

Introduction

Hello fellow ATV enthusiasts! If you’re reading this, chances are you’re considering upgrading your Honda 400Ex with a 440 big bore kit. As an experienced rider myself, I have gone through the process of researching and purchasing a big bore kit for my 400Ex. In this buying guide, I will share my first-hand experience and provide you with all the necessary information to make an informed decision on purchasing a 440 big bore kit for your 400Ex.

What is a 440 Big Bore Kit?

Before we dive into the details, let’s first understand what a 440 big bore kit is. A big bore kit is an engine upgrade that increases the displacement of your ATV’s engine. In simple terms, it makes your engine bigger and more powerful. The standard engine size for a Honda 400Ex is 397cc, and with a 440 big bore kit, it will increase to 440cc.

Why Upgrade to a 440 Big Bore Kit?

The main reason why riders opt for a big bore kit is to increase their ATV’s power and performance. A bigger engine means more horsepower and torque, resulting in improved acceleration and top speed. Additionally, having more power can come in handy when riding on challenging terrains or competing in races.

Finding the Right Kit

There are many options available when it comes to choosing a 440 big bore kit for your Honda 400Ex. It’s essential to do thorough research and consider factors such as brand reputation, customer reviews, and price before making your purchase.

  • Brand Reputation: It’s crucial to choose a reputable brand when purchasing any ATV part or accessory. Look for brands that have been in the market for some time and have positive reviews from customers.
  • Customer Reviews: Reading customer reviews can give you valuable insights into the performance of different big bore kits. Look for reviews from riders who have similar riding styles as yours.
  • Price: While it may be tempting to go for the cheapest option available, keep in mind that quality comes at a price. Invest in a good quality big bore kit that will last you longer rather than opting for cheaper alternatives that may compromise on performance.

Budget Considerations

Apart from the cost of the actual kit itself, there are other expenses involved when upgrading to a 440 big bore kit. These may include additional parts such as gaskets or jets, professional installation fees if you’re not confident in doing it yourself, or dyno tuning fees to optimize your new setup’s performance. Make sure to factor these costs into your budget before making your purchase decision.

The Installation Process

If you have basic mechanical knowledge and experience working on ATVs, installing a big bore kit can be done at home with proper tools and instructions provided by the manufacturer. However, if you’re not confident or don’t have access to tools required for installation, it’s best to seek professional help. Improper installation can result in damage to your engine and void any warranty provided by the manufacturer.

In Conclusion

A 440 big bore kit is an excellent investment if you want to take your Honda 400Ex’s performance to the next level. With proper research and budget considerations, finding the right kit shouldn’t be too challenging. Just remember always to follow manufacturer instructions during installation and break-in period after installation for optimal results.

I hope this buying guide has provided you with valuable insights into purchasing a 440 big bore kit for your Honda 400Ex. Happy riding!

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Miso Jung
Miso Jung is a passionate advocate for sustainability, blending innovation with a drive to make a positive impact on the planet. Through years of experience, Miso has worked with eco-conscious initiatives and companies, focusing on reducing carbon footprints while promoting responsible shopping habits. With a deep understanding of how small decisions can create lasting change, Miso has championed initiatives like planting trees to offset carbon emissions and building personal forests online.

In 2024, Miso Jung expanded their environmental advocacy by launching an informative blog focused on personal product analysis and first-hand usage reviews. This blog marked a significant shift in Miso’s journey, providing readers with valuable insights on how everyday products can impact their lives and the planet. Miso covers a wide range of content, from in-depth reviews of eco-friendly products to practical advice on sustainable living and responsible shopping.