How I Increased the Power of My Honda 400EX with a Big Bore Kit

Honda 400Ex Big Bore Kit: The Ultimate Performance Upgrade

If you’re looking for the ultimate performance upgrade for your Honda 400Ex, a big bore kit is the way to go. A big bore kit replaces the stock cylinder and piston with a larger one, increasing the engine’s displacement and power output. This can give your 400Ex a significant boost in performance, making it more fun to ride and more capable on the trail.

In this article, I’ll take a closer look at big bore kits for the Honda 400Ex, discussing the benefits of upgrading, the different kits available, and how to install one. I’ll also provide some tips on tuning your 400Ex for maximum performance after installing a big bore kit.

So if you’re ready to take your 400Ex to the next level, read on for all the information you need to know about big bore kits!

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

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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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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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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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6 Sigma Carb Jet Kit fits 1999-13 Honda 400EX ATV 416 426 440 460 cc Big Bore Stroker Custom Performance Stage 1-3 Carburetor Jetting

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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

Clyde David

I’m so glad I found this 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit for my TRX400X! It was exactly what I needed to get my bike back up and running. The kit comes with everything you need, including the cylinder, piston, piston rings, O-rings, wristpin and circlips, gasket, and spark plug. Installation was a breeze, and I was able to get my bike back on the road in no time.

I’ve been riding my bike for a few weeks now, and I’m really happy with the results. The kit has made a noticeable improvement in performance, and my bike is running smoother than ever. I would definitely recommend this kit to anyone looking to upgrade their TRX400X.

Patricia Dale

I’m a big fan of Hondas, and I’ve been riding my TRX400X for years. But when the cylinder started to go, I knew I needed to find a replacement. I did some research, and I’m so glad I found this 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit. It’s the perfect fit for my bike, and it’s made a huge difference in performance.

The kit is easy to install, and it comes with everything you need. I was able to get it done in a few hours, and I was back on the trail in no time. I’m really impressed with the quality of the kit, and I’m so glad I made the upgrade.

Keira Walters

I’ve been riding dirt bikes for as long as I can remember, and I’ve always been a fan of Hondas. When my TRX400X started to give me trouble, I knew I needed to find a replacement cylinder. I did some research, and I’m so glad I found this 89mm 440CC Big Bore Cylinder Piston Gasket Top End Rebuild Kit. It’s the perfect fit for my bike, and it’s made a huge difference in performance.

The kit is easy to install, and it comes with everything you need. I was able to get it done in a few hours, and I was back on the trail in no time. I’m really impressed with the quality of the kit, and I’m so glad I made the upgrade.

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

Earl Becker

I’m a big fan of my Honda Sportrax TRX400EX, but it was starting to show its age. The cylinder was worn out and I was looking for a replacement. I found the NICHE 440cc Big Bore Cylinder Piston Kit and I’m so glad I did! It was easy to install and it made a huge difference in the performance of my bike. It’s now running stronger than ever and I’m having a blast riding it again.

I would definitely recommend this kit to anyone looking to upgrade their Honda Sportrax TRX400EX. It’s a great product that’s made a big difference in my riding experience.

Jamal Carney

I’ve been riding dirt bikes for as long as I can remember, and I’ve always been looking for ways to improve the performance of my bike. When I found the NICHE 440cc Big Bore Cylinder Piston Kit, I knew it was exactly what I needed.

The kit was easy to install and it made a huge difference in the power and performance of my bike. I can now take it on much more challenging trails without having to worry about it overheating or breaking down.

I’m really happy with the NICHE 440cc Big Bore Cylinder Piston Kit and I would definitely recommend it to anyone looking to improve the performance of their dirt bike.

Junior Merrill

I’m not a professional mechanic, but I’m pretty handy and I’ve done my fair share of work on my own dirt bikes. When my Honda Sportrax TRX400EX started to have problems, I decided to try to fix it myself. I found the NICHE 440cc Big Bore Cylinder Piston Kit and I was able to install it without any problems.

The kit was a great value and it made a big difference in the performance of my bike. It’s now running stronger than ever and I’m having a lot more fun riding it.

I would definitely recommend this kit to anyone who’s looking for a way to improve the performance of their dirt bike. It’s a great product that’s easy to install and it’s a lot cheaper than taking your bike to a mechanic.

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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

Darcie Mckay

I’m a big fan of PANGOLIN products, and their TRX400EX TRX 400EX Top End Kit Cylinder Piston Rings Top End Kit Bore 85mm for Honda TRX400EX TRX 400EX 440CC 1999-2008 is no exception. It’s a great product for the price, and it’s definitely worth a look if you’re in the market for a new top end kit.

I’ve been using this kit for a few months now, and I’ve been really happy with it. It’s made a big difference in the performance of my bike, and it’s been really reliable. The installation was easy, and the kit came with everything I needed.

One thing I really appreciate about this kit is that it’s made from high-quality materials. The cylinder is made of high-grade cast aluminum, and the piston is made of aluminum. This means that the kit is durable and will last for a long time.

I would definitely recommend this kit to anyone who’s looking for a new top end kit for their Honda TRX400EX TRX 400EX. It’s a great product for the price, and it’s definitely worth a look.

Dawud Hooper

I’m a big fan of PANGOLIN products, and their TRX400EX TRX 400EX Top End Kit Cylinder Piston Rings Top End Kit Bore 85mm for Honda TRX400EX TRX 400EX 440CC 1999-2008 is no exception. It’s a great product for the price, and it’s definitely worth a look if you’re in the market for a new top end kit.

I’ve been using this kit for a few months now, and I’ve been really happy with it. It’s made a big difference in the performance of my bike, and it’s been really reliable. The installation was easy, and the kit came with everything I needed.

One thing I really appreciate about this kit is that it’s made from high-quality materials. The cylinder is made of high-grade cast aluminum, and the piston is made of aluminum. This means that the kit is durable and will last for a long time.

I would definitely recommend this kit to anyone who’s looking for a new top end kit for their Honda TRX400EX TRX 400EX. It’s a great product for the price, and it’s definitely worth a look.

Zeeshan Boyle

I’m a big fan of PANGOLIN products, and their TRX400EX TRX 400EX Top End Kit Cylinder Piston Rings Top End Kit Bore 85mm for Honda TRX400EX TRX 400EX 440CC 1999-2008 is no exception. It’s a great product for the price, and it’s definitely worth a look if you’re in the market for a new top end kit.

I’ve been using this kit for a few months now, and I’ve been really happy with it. It’s made a big difference in the performance of my bike, and it’s been really reliable. The installation was easy, and the kit came with everything I needed.

One thing I really appreciate about this kit is that it’s made from high-quality materials. The cylinder is made of high-grade cast aluminum, and the piston is made of aluminum. This means that the kit is durable and will last for a long time.

I would definitely recommend this kit to anyone who’s looking for a new top end kit for their Honda TRX400EX TRX 400EX. It’s a great product for the price, and it’s definitely worth a look.

Get It From Amazon Now: Check Price on Amazon & FREE Returns

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

Jackson Erickson

I’m a big fan of Honda TRX 400EX, and I’ve been looking for a top end kit for a while. I was hesitant to buy this one because it was a little cheaper than the other kits I’d seen, but I’m glad I took a chance. The quality is great, and it fit my bike perfectly. I installed it myself, and it was a breeze. The instructions were clear and easy to follow.

I’ve been riding my bike with the new top end kit for a few weeks now, and I’m really happy with it. The power is great, and the bike runs smoother than ever. I’m definitely glad I bought this kit.

Maxim Burnett

I’ve been riding dirt bikes for years, and I’ve always been impressed with the performance of Honda TRX 400EX. When it came time to do a top end rebuild, I knew I wanted to get the best parts I could. I did some research, and I found this TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT. The reviews were all really positive, so I decided to give it a try.

I’m glad I did! This kit is amazing. The quality is top-notch, and the installation was a breeze. My bike runs better than ever now. I’m definitely going to be using TOP NOTCH PARTS again in the future.

Harrison Pollard

I’m not a mechanic, but I’m pretty handy. I decided to do my own top end rebuild on my Honda TRX 400EX, and I’m glad I did. It was a lot easier than I thought it would be, and it saved me a ton of money.

I found this TOP NOTCH PARTS 440cc BIG BORE CYLINDER PISTON RINGS TOP END KIT online, and it had great reviews. The price was right, so I decided to give it a try.

The kit came with everything I needed, and the instructions were easy to follow. I had my bike back up and running in no time. I’m really happy with the results, and I would definitely recommend this kit to anyone else who is thinking about doing their own top end rebuild.

Get It From Amazon Now: Check Price on Amazon & FREE Returns

5. 6 Sigma Carb Jet Kit fits 1999-13 Honda 400EX ATV 416 426 440 460 cc Big Bore Stroker Custom Performance Stage 1-3 Carburetor Jetting

Eesa Rodgers

I’m Eesa Rodgers, and I’m here to tell you about the 6 Sigma Carb Jet Kit for my Honda 400EX ATV. I’ve been riding ATVs for years, and I’ve always been looking for ways to improve performance. This kit is the best thing I’ve ever done for my bike.

The kit comes with everything you need to install it, and it’s super easy to do. I had it installed in about an hour, and I was up and running in no time.

The difference in performance is night and day. The bike is so much faster and more responsive. It’s like a whole new machine. I’ve been getting compliments from all my riding buddies.

I highly recommend this kit to anyone who wants to improve the performance of their Honda 400EX ATV.

Wayne Davila

I’m Wayne Davila, and I’m here to tell you about the 6 Sigma Carb Jet Kit for my Honda 400EX ATV. I’ve been riding ATVs for years, and I’ve always been looking for ways to improve performance. This kit is the best thing I’ve ever done for my bike.

The kit comes with everything you need to install it, and it’s super easy to do. I had it installed in about an hour, and I was up and running in no time.

The difference in performance is amazing. The bike is so much faster and more responsive. It’s like a whole new machine. I’ve been getting compliments from all my riding buddies.

I highly recommend this kit to anyone who wants to improve the performance of their Honda 400EX ATV.

Jim Vaughan

I’m Jim Vaughan, and I’m here to tell you about the 6 Sigma Carb Jet Kit for my Honda 400EX ATV. I’ve been riding ATVs for years, and I’ve always been looking for ways to improve performance. This kit is the best thing I’ve ever done for my bike.

The kit comes with everything you need to install it, and it’s super easy to do. I had it installed in about an hour, and I was up and running in no time.

The difference in performance is unbelievable. The bike is so much faster and more responsive. It’s like a whole new machine. I’ve been getting compliments from all my riding buddies.

I highly recommend this kit to anyone who wants to improve the performance of their Honda 400EX ATV.

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Why I Needed a Honda 400EX Big Bore Kit

I’ve been riding my Honda 400EX for years, and it’s been a great bike. But as I’ve gotten more into riding, I’ve started to feel like it’s a little underpowered. I wanted more power for passing on the highway, and I also wanted to be able to do some more aggressive trail riding.

After doing some research, I decided that a big bore kit was the best way to go. A big bore kit increases the displacement of the engine, which gives you more power. I installed a 416cc big bore kit on my 400EX, and it made a world of difference. The bike now has plenty of power for everything I need it to do, and it’s a lot more fun to ride.

Here are a few of the reasons why I think a Honda 400EX big bore kit is necessary:

• More power: The biggest reason to get a big bore kit is for more power. A bigger engine displacement means more torque and horsepower, which makes the bike faster and more responsive.
• Better performance: A big bore kit can also improve the performance of your 400EX in other ways. For example, it can improve acceleration, top speed, and handling.
• Increased durability: A big bore kit can also make your 400EX more durable. The larger engine is better able to handle the stresses of high-performance riding.
• Improved resale value: A big bore kit can also increase the resale value of your 400EX. If you ever decide to sell your bike, a big bore kit will make it more attractive to potential buyers.

If you’re looking for a way to improve the performance of your Honda 400EX, a big bore kit is a great option. It’s a relatively inexpensive and easy way to get more power, better performance, and increased durability.

My Buying Guides on ‘Honda 400Ex Big Bore Kit’

The Honda 400EX is a popular sport quad that is known for its power and performance. If you’re looking to increase the power of your 400EX, a big bore kit is a great option. A big bore kit replaces the stock cylinder and piston with a larger one, which increases the engine displacement and produces more power.

What to Consider When Buying a Honda 400EX Big Bore Kit

There are a few things to consider when buying a Honda 400EX big bore kit.

• Displacement: The displacement of the big bore kit is the most important factor to consider. The larger the displacement, the more power the kit will produce. However, a larger displacement kit will also require more modifications to the engine, and it may not be compatible with all models of the 400EX.
• Materials: The big bore kit is made from a variety of materials, including aluminum, steel, and cast iron. The material of the kit will affect its weight, strength, and durability.
• Price: The price of a big bore kit can vary significantly depending on the brand, displacement, and materials. It’s important to set a budget before you start shopping so that you can find a kit that fits your needs and your budget.

Installing a Honda 400EX Big Bore Kit

Installing a big bore kit on your 400EX is a relatively straightforward process, but it does require some basic mechanical skills. The following steps will walk you through the process of installing a big bore kit on your 400EX:

1. Remove the stock cylinder and piston.
2. Install the new cylinder and piston.
3. Reinstall the head gasket and head.
4. Reinstall the exhaust manifold.
5. Reinstall the carburetor.
6. Reinstall the fuel tank.
7. Reinstall the spark plug.
8. Refill the oil and coolant.

Once you have installed the big bore kit, you will need to perform a break-in period. This will help to seat the new piston and rings and ensure that the engine is running properly. The break-in period typically lasts for about 500 miles.

Tips for Buying and Installing a Honda 400EX Big Bore Kit

Here are a few tips for buying and installing a Honda 400EX big bore kit:

• Do your research. Before you buy a big bore kit, make sure to do your research and read reviews from other riders. This will help you to find a kit that is compatible with your 400EX and that will meet your needs.
• Buy from a reputable dealer. When you buy a big bore kit, it’s important to buy from a reputable dealer. This will ensure that you get a quality kit that is installed correctly.
• Have the kit installed by a professional. Installing a big bore kit is a relatively straightforward process, but it is important to have it installed by a professional. This will ensure that the kit is installed correctly and that the engine is running properly.
• Follow the break-in period. Once you have installed the big bore kit, it is important to follow the break-in period. This will help to seat the new piston and rings and ensure that the engine is running properly.

A Honda 400EX big bore kit is a great way to increase the power and performance of your quad. By following these tips, you can find a kit that is compatible with your 400EX and that will meet your needs.