Honda 400EX Rebuild Kits: Powering Your Ride

The Honda 400EX, also known as the TRX400EX or SporTrax, has long been a favourite among ATV enthusiasts. Renowned for its reliability, power, and sheer fun factor, this machine laid the groundwork for many modern sport ATVs and played a significant role in introducing four-stroke engines to the ATV landscape. If you're looking to revitalise your 400EX, a comprehensive rebuild kit is the way to go. We offer the best 400EX Rebuild Kits of all sizes at the best prices, period. Having sold thousands of these kits, we stand behind our products with a solid 1-year warranty, complete with installation and tech support included with your purchase.

What is a 400EX Rebuild Kit?

A rebuild kit for your Honda 400EX is a collection of essential components designed to restore your engine to its optimal performance, or even enhance it. These kits typically include a new piston, piston rings, wrist pin, circlips, and a top-end gasket set. For those looking to push their machine further, many kits also offer upgrades such as high-performance pistons, advanced gasket materials, and even improved ignition components.

Our Premium 400EX Rebuild Kit Components

When you choose our rebuild kits, you're investing in quality and performance. Here's what you can expect:

• BPRATV 87mm Nikasil Big Bore Cylinder (1 Year Warranty): For those seeking that extra displacement and power. Nikasil plating offers superior wear resistance and heat dissipation.
• Wiseco, JE, CP, or Wossner Forged Piston*: Renowned manufacturers of high-performance pistons, ensuring durability and optimal compression. The choice of piston may vary, but the quality remains paramount.
• Hi-Temp Piston Rings: Designed to withstand the higher temperatures associated with performance engines.
• Wristpin: Essential for connecting the piston to the connecting rod.
• Circlips: Securely hold the wristpin in place.
• Talon Titanium Head Stud Kit with Life Warranty*: A significant upgrade for improved cylinder head sealing and engine durability under stress.
• Cometic Big Bore MLS Top End Gasket Kit: Multi-Layer Steel (MLS) gaskets provide superior sealing for big bore applications, resisting blowouts and leaks.
• Valve Stem Seals: Crucial for preventing oil consumption and maintaining proper valve function.
• Heavy Duty Timing Chain: A more robust timing chain ensures reliable timing, especially with increased power output.
• NGK Spark Plug: A quality spark plug to ensure optimal ignition.
• Full 1 Year Warranty on the Complete Kit*: We back our kits with confidence.

*Note: Specific piston manufacturers and warranty details may vary. Please check product descriptions for exact specifications.

Why Rebuild Your Honda 400EX?

Over time, even the most robust engines experience wear. For your 400EX, this can manifest as a loss of power, increased oil consumption, or even starting issues. Rebuilding your engine with a quality kit can:

• Restore Lost Power: Worn piston rings and cylinders reduce compression, leading to a noticeable drop in performance.
• Improve Reliability: Fresh components minimise the risk of unexpected breakdowns.
• Enhance Performance: With a big bore kit or performance piston, you can actually increase your 400EX's power output.
• Extend Engine Life: A thorough rebuild with quality parts can give your engine many more years of service.

Understanding the Honda 400EX (TRX400EX/SporTrax)

Launched as part of the SporTrax lineup, the 2002 Honda 400EX was a game-changer. It revived the sport-ATV segment and championed the four-stroke engine in a market often dominated by two-strokes. Its XR400R-inspired engine, coupled with a robust chassis and capable suspension, made it an instant hit.

Key Specifications of the 2002 Honda 400EX:

The 400EX boasts an air-cooled, single-cylinder, 4-stroke engine with a displacement of 397cc. It features a 5-speed transmission and a multi-plate wet clutch. The suspension system includes independent double-wishbone front suspension with Showa shocks (8.2 inches of travel) and a Pro-Link rear suspension with a single Showa shock (9.1 inches of travel). Braking is handled by dual front disc brakes and a single rear disc brake.

Common Honda 400EX Issues and How Rebuild Kits Help

While the 400EX is known for its robustness, like any machine, it can develop issues over time. A rebuild kit directly addresses many of these:

• Engine Won't Start: While this can be due to battery or fuel issues, internal engine wear (worn piston rings, low compression) can also prevent starting. A new piston and rings will restore compression.
• Loss of Power: This is a classic symptom of worn piston rings and cylinder walls. Our kits, especially with a big bore option, will bring back that lost horsepower.
• Increased Oil Consumption: Worn piston rings can allow oil to enter the combustion chamber, leading to blue smoke and fouled spark plugs. New rings create a better seal.
• Engine Noise: Piston slap or excessive ring noise can be indicative of wear that a rebuild kit will resolve.

Installation and Warranty Considerations

We strongly recommend that this kit be installed by a qualified mechanic experienced with these types of motors. Improper installation, tuning, or break-in procedures can lead to premature failure and will void the warranty. The piston comes with specific instructions for setting the ring gap – these must be followed precisely.

For any warranty claim to be considered, the part(s) in question must first be sent to us, and potentially the manufacturer, for inspection. We cannot warranty parts based solely on photos or phone calls.

When Did Honda Replace the 400EX?

Honda did not directly 'replace' the 400EX with a single successor in the same vein. Instead, the market evolved, and Honda introduced other models that catered to different segments and advancements in ATV technology. The 400EX's production run spanned a significant period, and while it remained largely unchanged, the ATV landscape continued to advance. Riders looking for more modern features or different power characteristics might have moved to other Honda models or brands as they emerged.

Who Makes the Honda 400EX?

The Honda 400EX (TRX400EX) is manufactured by the Honda Motor Company, a Japanese multinational conglomerate renowned for its automotive and powersports products. Honda is a pioneer in the sport-ATV segment, and the 400EX is a testament to their engineering prowess and understanding of rider needs.

What if I'm Not Happy with My Honda 400EX Rebuild Kit?

Your satisfaction is our priority. Please check your order thoroughly upon receiving it. If, for any reason, you are not 100% happy with your purchase prior to installing the parts, you are welcome to return it for a full refund, no questions asked. We are here to help resolve any issues you may encounter. CONTACT US FOR ALL YOUR HONDA 400EX NEEDS!

Frequently Asked Questions

Q1: Can I use this kit for my XR400R dirt bike?

A1: Yes, our kits are designed to fit all Honda 400EX, 400X, and XR400 models and years, provided the bore size matches your requirements (e.g., 85mm stock bore or big bore options).

Q2: Do I need any special tools for installation?

A2: While a standard mechanic's toolkit is necessary, specific tools like a torque wrench, piston ring compressor, and potentially a valve spring compressor are highly recommended for a proper engine rebuild. We advise consulting a service manual for detailed tool requirements.

Q3: What is the recommended break-in procedure after installing the kit?

A3: Proper break-in is crucial. Typically, this involves varying engine speeds, avoiding prolonged idling, and gently increasing the load over the first few hours of operation. Refer to the specific instructions provided with your piston and rings, or consult your service manual for detailed break-in procedures. Failure to follow these can lead to engine failure.

Q4: My 400EX is smoking after the rebuild. What could be wrong?

A4: Smoking can indicate several issues, most commonly incorrect installation of piston rings (upside down or incorrect gap), damaged valve stem seals, or issues with the valve guides. Double-check the ring orientation and gap, and ensure valve stem seals were installed correctly. Ensure you followed the break-in procedure meticulously.

Q5: Can I mix and match parts from different manufacturers?

A5: While technically possible, we strongly advise against mixing components from different manufacturers unless specifically designed to work together. Our kits are balanced and tested for compatibility. Using mismatched parts can lead to poor performance, premature wear, and potential engine damage.

Revitalise your Honda 400EX and experience the thrill of a freshly rebuilt engine. With our high-quality components, comprehensive support, and commitment to customer satisfaction, you can trust us to help you get back to what you love – riding! BRAPPPPPPPPPP!