Honda TRX400EX / 400X 89mm Big Bore Kit – Stage 3 Cam & Studs

SKU 265234110730

💥 Honda TRX400EX / 400X / XR400R Big Bore Kit – 89mm Cylinder + Stage 3 Performance
Bolt-On Power – No Case or Head Boring Required

Take your Honda 400EX or 400X to the next level with this complete 89mm big bore kit, designed for high performance and durability while maintaining compatibility with your stock cylinder head and bottom end. Built for aggressive trail riding, dunes, or racing, this package delivers noticeable gains without requiring major engine mods.

✅ Fits all 1999–2008 TRX400EX, 2009–2014 TRX400X, and most XR400R models
✅ Uses stock head and cases – no boring required
✅ 1-Year Warranty – All parts covered against manufacturing defects

📦 What's Included:

• 🔥 BPR 89mm Big Bore Cylinder – Brand new, ready to install

• ⚙️ Wiseco, CP, or JE Forged Big Bore Piston

• 🔩 Kibblewhite Heavy Duty Valve Spring Kit

• 🏁 Hotcams Stage 3 Camshaft – More lift and duration

• 🔗 Heavy Duty Cam Chain

• 🧰 Cometic or Athena Top End Gasket Kit

• 🏎️ Athena Big Bore MLS Head Gasket

• 🔒 Kibblewhite Cylinder Head Stud Kit – Superior clamping force

• 🔄 Viton Valve Stem Seals

• 🎁 Installation Instructions + Stickers

⚙️ Key Benefits:

• 🚀 More Power: 89mm bore boosts compression and flow

• 🧩 Complete Kit: No need to source extra parts

• 🔧 Easy Installation: Bolt-on – no machining of head or cases

• 🛠️ Built for Performance: Forged piston and HD components

• ⛽ Fuel Flexibility: Runs on pump or race gas

📌 Fitment Compatibility:

• 1999–2008 Honda TRX400EX

• 2009–2014 Honda TRX400X

• 1996–2004 Honda XR400R (check cylinder style for head compatibility)

📦 Shipping Time:
Ships within 3–5 business days. Tracking provided upon shipment.

💬 Customer Support:
Available Monday–Friday, 7 AM to 4 PM PST
24/7 live store chat support