Honda 400EX 400X 88mm Big Bore Kit Valves Springs Stage 2 Hotcam +3 426c Top End

Honda TRX400EX TRX400X 426cc 88mm Big Bore Top End Kit Hot Cams Stage 2 +3mm

📖 Product Description

Take your Honda TRX400EX or TRX400X to the next level with this complete 426cc 88mm Big Bore Top End Rebuild Kit. Designed for riders looking for increased horsepower, stronger torque, and improved throttle response, this package combines premium components including an 88mm cylinder, forged piston, hardened steel valves, upgraded valve springs, and a Hot Cams Stage 2 Camshaft for proven performance gains throughout the RPM range.

This setup increases displacement by approximately +26cc over stock and is engineered to deliver reliable performance on either pump gas or race fuel. No cylinder head modifications or crankcase machining are required, making this one of the most popular performance upgrades available for the legendary Honda 400EX platform.

🔥 Key Features & Benefits

• 88mm big bore cylinder increases displacement to approximately 426cc
• Wiseco or Wossner forged piston kit for maximum durability and performance
• Hot Cams Stage 2 camshaft delivers stronger mid-range and top-end power
• hardened steel valves improve airflow and cylinder filling
• Heavy-duty valve springs and retainers support higher RPM operation
• HD timing chain improves timing stability and longevity
• Talon Titanium cylinder stud kit provides superior clamping force and corrosion resistance
• Cometic gasket kit ensures reliable sealing under demanding conditions
• No head or case modifications required for installation
• Compatible with pump gas or race fuel

📦 Product Contents

• 88mm big bore cylinder
• Wiseco or Wossner forged piston
• High-temperature piston rings
• Chrome wrist pin
• Piston circlips
• Cometic top-end gasket kit
• Hot Cams Stage 2 camshaft
• Camshaft bearings
• Talon Titanium cylinder stud kit
• Heavy-duty timing chain
• Hardened steel intake valves
• Hardened steel exhaust valves
• Valve springs
• Valve retainers
• Viton valve stem seals

✅ Compatibility

Designed for Honda's proven air-cooled sport ATV platform and compatible with stock engine cases and cylinder heads.

• Honda TRX400EX (1999-2008)
• Honda TRX400X (2009-2014)
• 426cc 88mm big bore performance builds
• Stock stroke applications
• No crankcase machining required

❓ FAQ

• Q: Does this kit require machining of the cases?

  A: No. This 88mm big bore kit installs without any crankcase machining or modifications.

• Q: Can I run pump gas with this setup?

  A: Yes. This package is designed to operate on pump gas or race fuel depending on your tuning and riding requirements.

• Q: What camshaft is included?

  A: A genuine Hot Cams Stage 2 camshaft is included for improved horsepower, torque, and throttle response.

• Q: Are upgraded valves included?

  A: Yes. The kit includes hardened steel intake and exhaust valves, upgraded valve springs, retainers, and Viton valve stem seals.

• Q: Is this covered by warranty?

  A: Yes. This kit includes a 6-month warranty against manufacturing defects.

🌟 Why Buy from BPRATV

At BPRATV, our promise is unwavering: The Best Parts. The Best Performance. The Best Price. We specialize in high-performance powersports components trusted by riders and builders who demand reliability and results. Every part is carefully selected for precision, durability, and real-world performance. Trust BPRATV to keep your Honda TRX400EX and TRX400X running at its best, every single time. 

Build your ultimate Honda 400EX/400X engine with this complete 426cc big bore performance package today! 

BPRATV - The Best Parts. The Best Performance. The Best Price.
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© BPRATV LLC

Due to the nature of high performance and racing applications, BPRATV LLC components are sold without express warranty or any implied warranty of merchantability or fitness for a specific purpose. BPRATV LLC shall not, under any circumstances, be liable for any specific, incidental or consequential damages, including, but not limited to, damage, or loss of property or equipment, loss of profits or revenue(s), cost of purchased or replacement goods, or claims of customers of the purpose, which may arise and/or shall result from sale, installation or use of these parts. Installation of these parts may void vehicle manufacturers warranty coverage and/or may cause the vehicle to be illegal in some locations.

This product is exempt from the emission standards and related requirements of 40 C.F.R. §1051 as provided by 40 C.F.R. §1051.620, and California law. This product is sold only for use in connection with EPA-certified, purpose-built, nonroad vehicles used solely for closed-course, nonroad competition/racing.