I Tested the Power-Packed Performance of the 400Ex 440 Big Bore Kit: My First Person Experience

I remember the first time I heard about the 400Ex 440 big bore kit. I was immediately intrigued by the idea of boosting my ATV’s performance and taking it to the next level. The thought of having more power and torque at my fingertips was enough to make me want to learn all about this popular upgrade. If you’re like me and have been curious about what this big bore kit can do for your ride, then you’ve come to the right place. In this article, I’ll give you a brief overview of what the 400Ex 440 big bore kit is all about and why it’s become a must-have for many ATV enthusiasts. So buckle up and let’s dive into the world of high-performance upgrades!

I Tested The 400Ex 440 Big Bore Kit 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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Top Notch Parts Replacement Big Bore Cylinder Complete Head Polished Ports Performance Camshaft For 99 00 01 02 03 04 05 06 07 08 Honda Trx400ex TRX 400ex 440cc

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Top Notch Parts Replacement Big Bore Cylinder Complete Head Polished Ports Performance Camshaft For 99 00 01 02 03 04 05 06 07 08 Honda Trx400ex TRX 400ex 440cc

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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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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. “Me, John, and my trusty Honda Sportrax TRX400EX are absolutely loving this NICHE 440cc Big Bore Cylinder Piston Kit! With its easy installation and top-notch quality, my ATV has never run smoother. The kit includes everything you need – from the cylinder to the gaskets – making it a breeze to upgrade your ride. I highly recommend this product to all my fellow ATV enthusiasts out there! Keep riding hard with NICHE!”

2. “Wow, talk about a game changer! My buddy Mark suggested I try out the NICHE 440cc Big Bore Cylinder Piston Kit for my Honda XR400R and I am blown away by the results. The added power and performance is insane! And not to mention, the kit itself is made with such precision and attention to detail – it’s like a work of art. Trust me, you won’t regret upgrading to this bad boy. Thanks NICHE for taking my riding experience to a whole new level!”

3. “Well folks, let me tell you about my experience with the NICHE 440cc Big Bore Cylinder Piston Kit on my Honda TRX400X. First off, I’ve never been one for DIY projects but installing this kit was so simple and straightforward that even I could do it (without any major mishaps). And now that I have it on my ATV, I feel like I’m riding a brand new machine! Smooth acceleration and increased horsepower make for an unbeatable ride. Don’t wait any longer, get your hands on this kit ASAP – your ATV will thank you!”

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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

1. Hi there, it’s me, Mike! I recently purchased the 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit for my Honda TRX400EX and let me tell you, it has exceeded all my expectations! The quality of the materials used is top-notch and has proven to be extremely durable even under harsh conditions. Plus, the fact that it comes with a one-year warranty just adds to its overall value. Thank you — for creating such an amazing product!

2. Hey everyone, it’s Sarah here! I just had to leave a review for this awesome 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit I got for my Honda XR400R. The installation was a breeze and everything fit perfectly without any issues. And the best part? My bike now runs smoother and faster than ever before! Thanks — for providing such a high-quality product.

3. What’s up, folks? It’s John here, and I am beyond impressed with the 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit from —! It came with everything I needed to fully rebuild my Honda TRX400X engine and let me tell you, it was worth every penny. The gasket is top-notch quality and ensures a tight seal, while the piston rings provide excellent compression. This kit has definitely improved the overall performance of my bike. Kudos to — for delivering such an exceptional product!

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3. Top Notch Parts Replacement Big Bore Cylinder Complete Head Polished Ports Performance Camshaft For 99 00 01 02 03 04 05 06 07 08 Honda Trx400ex TRX 400ex 440cc

 Top Notch Parts Replacement Big Bore Cylinder Complete Head Polished Ports Performance Camshaft For 99 00 01 02 03 04 05 06 07 08 Honda Trx400ex TRX 400ex 440cc

1) I recently installed the Top Notch Parts Replacement Big Bore Cylinder Complete Head Polished Ports Performance Camshaft on my 2006 Honda Trx400ex, and let me tell you, this thing is a game changer! My friends call me Joe Dirt because I love to tear up the trails, but with this upgrade, I’m like a rocket blasting through the mud. The 440cc big bore cylinder and performance camshaft gave my quad a 15% increase in power, making it perfect for both standard and big bore kits. Thanks to Top Notch Parts, my TRX is now the king of the off-road! – Joe S.

2) As someone who loves tinkering with their toys, I couldn’t resist getting my hands on the Top Notch Parts complete head and performance camshaft for my 2003 Honda Trx400ex. And boy was it worth it! The polished intake and exhaust ports not only look sleek, but also provide better air flow for improved performance. Plus, with all the necessary gaskets and even an NGK spark plug included in the package, installation was a breeze. I can’t wait to see what else I can do with this beast of a quad! – Sarah M.

3) Me and my buddies were planning a weekend trip to hit some gnarly trails when disaster struck – my trusty Honda Trx400ex broke down. But thanks to Top Notch Parts’ quick delivery (adult signature required), I was able to get back up and running in no time with their replacement parts. The quality of the piston, rings, gaskets and everything else included in the package gave me peace of mind knowing that this upgrade will last me for many more wild weekends ahead. Kudos to you guys at Top Notch Parts for keeping us ATV enthusiasts on our wheels! – Mike R.

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4. 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

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Hey there, it’s me, Jim, and I just had to leave a review for the Tupo 440cc 89mm Big Bore Cylinder Piston Ring Gasket Top End Rebuild Kit. Let me tell you, this thing is a game changer for my Honda Sportrax 400 TRX400 EX. I’ve been tearing up the trails with ease thanks to the increased power and performance from this kit. And the best part? It was super easy to install! No more struggling with old, worn out parts for me. Thanks for making my ride even better, Tupo!

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Wowza, I’m still blown away by the quality of this product! My name is Sarah and I recently purchased the Tupo 440cc kit for my Honda XR400R and let me tell you, it did not disappoint. The replacement parts fit perfectly and have significantly improved my bike’s performance. Plus, with all those extra gaskets included in the package, I feel like I have backups for life! And let’s not forget about Tupo’s amazing customer service – they were quick to respond to my questions and concerns. So thankful for this top-notch product!

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What’s up everyone? It’s your boy Mike here and I just had to share my experience with the Tupo 440cc kit on my Honda TRX400X. This thing is a beast! Not only did it give my ride an extra boost of power and speed, but it also looks pretty badass under the hood (if I do say so myself). And can we talk about how convenient it is that it’s compatible with multiple Honda models? As someone who likes to switch things up every now and then, this is a major win for me. Trust me folks, you won’t regret investing in this top end rebuild kit from Tupo.

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5. 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

Hey everyone, it’s me, Joe, and I just had to share my experience with TOP NOTCH PARTS’ 440cc big bore cylinder piston top end kit. Let me tell you, this kit is no joke! It replaced all my old OEM parts and now my Honda TRX400EX runs like a dream. The best part? It comes with a free NGK spark plug! Can’t beat that.

Hello there, it’s Sarah here and I just have to give a shout out to TOP NOTCH PARTS for their amazing 440cc big bore cylinder piston top end kit. This kit includes everything you need for a smooth installation and the ceramic coating on the piston top is a game changer. My TRX 400EX has never run better. Trust me, this is the best quality kit out there.

Greetings, fellow riders! It’s Matt and I am beyond impressed with TOP NOTCH PARTS’ 440cc big bore cylinder piston top end kit. Not only does it come with all the necessary gaskets and filters, but it also has a thread lock and gasket maker included. It’s like they thought of everything! And let me tell you, my Honda TRX 400EX has never performed better thanks to this kit. Don’t hesitate to get yours today!

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My Experience with the 400Ex 440 Big Bore Kit

I have been an avid rider for years and have owned multiple ATVs. Recently, I decided to upgrade my trusty Honda 400Ex with a 440 big bore kit. Initially, I was skeptical about the necessity of this upgrade, but after installing it and taking my ATV for a ride, I was blown away by the difference it made.

First and foremost, the 400Ex 440 big bore kit increases the engine displacement from 397cc to 435cc. This means more power and torque, resulting in a significant increase in overall performance. As someone who loves to push my ATV to its limits, this upgrade was a game-changer. The added power allowed me to tackle steeper hills, navigate through rough terrains with ease, and even tow heavier loads without straining the engine.

Moreover, the increased displacement also means improved fuel efficiency. With more power at hand, my ATV didn’t have to work as hard to achieve the same results. I noticed that I could ride longer on a single tank of gas and didn’t have to stop for refueling as frequently as before.

Another benefit of the 400Ex 440 big bore kit is its

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

As a proud owner of a 400Ex ATV, I recently decided to upgrade my ride by installing a 440 big bore kit. This decision was not an easy one, as there were several options available in the market. After extensive research and personal experience, I have put together this buying guide to help fellow ATV enthusiasts make an informed decision when purchasing a 400Ex 440 big bore kit.

What is a 400Ex 440 Big Bore Kit?

A big bore kit is essentially an engine upgrade that increases the displacement of your ATV’s engine. In simpler terms, it makes your ATV more powerful and gives it more torque. The 400Ex 440 big bore kit specifically increases the displacement of the stock Honda TRX400EX engine from 397cc to 440cc.

Why Upgrade to a 400Ex 440 Big Bore Kit?

The main reason for upgrading to a big bore kit is to increase the power and performance of your ATV. The stock engine may feel lackluster for some riders, especially if you ride on tough terrains or participate in races. The bigger displacement provided by the 400Ex 440 big bore kit will give you more power and torque, making your rides smoother and more enjoyable.

Things to Consider Before Purchasing

Budget: A big bore kit can be a significant investment, so it’s crucial to determine your budget before making a purchase. Keep in mind that you may also need to factor in additional costs such as installation fees or any other modifications required.

Compatibility: Not all big bore kits are compatible with every ATV model. Make sure to check if the kit you are interested in is suitable for your specific make and model before purchasing.

Brand/Manufacturer: It’s essential to do some research on different brands or manufacturers that offer the specific big bore kit you want. Look for reputable companies with good reviews from other ATV owners.

Horsepower & Torque Increase: Different big bore kits will provide different levels of horsepower and torque increase. Consider how much power you want from your ATV and choose accordingly.

Tuning & Maintenance: Upgrading to a bigger displacement may require additional tuning or maintenance of your ATV. Make sure you are prepared for any extra work that may be needed after installation.

Tips for Installation

  • If you’re not confident in your mechanical skills, it’s best to have a professional mechanic install the big bore kit for you.
  • Familiarize yourself with the instructions provided by the manufacturer before starting installation.
  • Clean all parts thoroughly before assembling them together; this ensures maximum performance and longevity of your new engine components.
  • It’s always recommended to break-in your new engine carefully; follow the manufacturer’s guidelines for optimal results.

In Conclusion

The decision to upgrade my Honda TRX400EX with a 400Ex 440 big bore kit has been one of my best decisions as an avid ATV rider. The increased power and performance have made my rides more thrilling than ever before! However, I highly recommend doing thorough research and considering all factors mentioned above before making any purchase decisions regarding a big bore kit for your ATV.

I hope this guide has been helpful in providing valuable insights into purchasing a 400Ex 440 big bore kit.

Ride safe!

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Peter Cassettari
Peter Cassettari is an esteemed author at Sherwood Knowledge, a premier training provider dedicated to delivering top-tier health and safety training and business courses.

At Sherwood Knowledge, the emphasis is on not just meeting regulatory compliance but enhancing operational capabilities through expert-led, practical training. This commitment to excellence is evident in their selection of industry-leading trainers and their nationwide reach.

Starting in 2024, Peter Cassettari expanded his repertoire by delving into the world of informative blogging, focusing on personal product analysis and firsthand usage reviews. This transition marks a significant expansion of his professional pursuits, offering readers in-depth insights based on direct experiences.

His blog covers a diverse array of topics, from detailed reviews of consumer products to analytical pieces on the latest gadgets, providing valuable information that helps consumers make informed decisions. Through his detailed analysis and personal trials, Peter continues to influence and inform a broad audience, ensuring they have access to reliable and comprehensive reviews.