99-04 Honda 400EX 88mm Big Bore Cylinder Crank Wiseco Piston Engine Rebuild Kit

99-04 Honda TRX 400EX 426cc 88mm Big Bore Wiseco Crank Rebuild Kit

🔥 Key Features & Benefits – 426cc Big Bore Power

Unleash the true potential of your Honda TRX 400EX with the BPRATV 99-04 Honda TRX 400EX 426cc 88mm Big Bore Wiseco Engine Rebuild Kit. This performance-focused package combines a big bore cylinder, forged Wiseco piston, heavy-duty crank assembly, and premium Cometic gaskets to deliver stronger acceleration, improved throttle response, and race-ready reliability in one complete solution.

📦 Complete Engine Rebuild Kit – What You Get

Every component in this BPRATV big bore rebuild kit is brand new and engineered to work together for a smooth, powerful 426cc setup. Designed specifically for 1999-2004 Honda TRX 400EX models, this kit gives you everything you need to refresh your top and bottom end with proven performance parts you can trust.

• BPRATV 88mm big bore cylinder – new, direct-bolt replacement with 1-year warranty for dependable performance.
• Wiseco forged 88mm piston kit – includes piston, rings, wrist pin, and clips for maximum strength and efficiency.
• Wiseco heavy-duty bottom end rebuild kit – OEM replacement crankshaft assembly with connecting rod plus Koyo/NTN main crank bearings.
• Complete Cometic gasket kits – bottom end gasket set and top end kit with big bore MLS head gasket for superior sealing.
• Engine oil seal kit & Viton valve stem seals – high-quality seals for long-lasting, leak-free operation on pump or race gas.

✅ Compatibility & Fitment Details

This complete 426cc upgrade is engineered for a precise fit on your Honda TRX 400EX, delivering a true big bore performance gain without guesswork. Whether you are trail riding, dune blasting, or racing, this combo is built to handle hard use while maintaining reliability.

• Designed exclusively for 1999-2004 Honda TRX 400EX models (all trim levels).
• 88mm big bore configuration yields approximately 426cc with the included crank setup.
• Direct bolt-on for compatible engines when assembled correctly – no case boring typically required.
• Works great with stock or mildly modified heads, carburetors, and exhaust systems.
• Ideal for riders wanting a strong, reliable power increase with all-new components in factory-style packaging.

❓ Frequently Asked Questions (FAQ)

• Q: Does this kit include everything needed for a full engine rebuild?

  A: This kit includes a new 88mm big bore cylinder, Wiseco forged piston kit with rings, wrist pin, and clips, a heavy-duty crankshaft assembly with rod, Japanese Koyo/NTN main bearings, complete top and bottom end Cometic gasket kits with big bore MLS head gasket, an engine oil seal kit, and Viton valve stem seals. You will reuse external hardware and valvetrain components unless you choose to upgrade them separately.

• Q: Does the BPRATV 88mm cylinder come ready to install?

  A: Yes. The BPRATV big bore cylinder is machined and prepared to work with the included Wiseco 88mm piston. We still recommend checking clearances, ring end gap, and piston-to-wall measurements as part of any professional engine build.

• Q: Do I need to modify the engine cases or head for this 426cc kit?

  A: For typical 99-04 Honda TRX 400EX builds, this 88mm big bore setup is intended as a direct bolt-on combination when assembled correctly. No case boring is usually required, but always verify clearances during mock-up and have a qualified engine builder perform any necessary checks or minor adjustments.

• Q: What fuel and break-in procedure do you recommend?

  A: For most builds we suggest premium pump gas (91+ octane) and proper heat-cycle break-in: short, gentle runs with full cool-downs, followed by gradual increases in load and RPM. Always use high-quality oil, change it early after break-in, and monitor for any leaks or abnormal noises before riding aggressively.

🌟 Why Buy from BPRATV? Trusted Honda 400EX Performance Experts 🌟

At BPRATV, our promise is unwavering: The Best Parts. The Best Performance. The Best Price. Every component in this Honda TRX 400EX 426cc big bore rebuild kit is carefully selected for strength, reliability, and value, so you get more power without sacrificing dependability. From the forged Wiseco piston and heavy-duty crank to the premium Cometic gaskets and Viton seals, we focus on parts that help you spend more time riding and less time wrenching. Trust BPRATV to keep your Honda TRX 400EX running at its best, every single time.

Ready to feel the difference of a true 426cc big bore? Click Buy It Now and let BPRATV power up your 400EX today!

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

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© BPRATV LLC 1-year limited warranty from the manufacturer for material or workmanship defects.*

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 [e.g., vehicle code§§ 27156 and 38391]. This product is sold only for use in connection with EPA -certified, purpose-built, nonroad vehicles used solely for closed course, nonroad competition/racing and not used for any recreational purpose or on public highways or right of ways maintained by and open to the public. This product is sold only in connection with machines that do not fall under state and/or federal noise or emission standards/regulations. Purchasers who/that purchase this product represent and warrant that the product is purchased only in connection with EPA -certified, emission-regulations-exempt and noise-regulations-exempt competition/racing vehicles as interpreted under applicable state and/or federal law.