Honda 400EX Top End Rebuild Kit – 85mm Wiseco Piston

🔥 Honda 400EX / 400X / XR400R Top End Rebuild Kit – 85mm Stock Bore, Wiseco Piston
Restore Compression, Power, and Reliability with This All-Inclusive Cylinder Assembly Kit

What’s Included:

• Dune Goons 85mm Cylinder (Stock Bore)

• Wiseco 85mm Forged Piston 10:1 – Part# 4606M08500

• Nitrite-Coated Piston Rings

• Chrome Wrist Pin & Circlips

• Athena Top End Gasket Kit Including Valve Cover and Valve Stem Seals - 400210600404
• NGK Spark Plug - DPR8Z

Key Features & Benefits:

🔧 Complete Top End Refresh in One Kit
Everything you need for a reliable top end rebuild on your 400EX, 400X, or XR400R.

🛠️ Performance-Grade Components
Wiseco forged piston offers durability and power, while nitrite rings and Cometic gaskets ensure long-lasting, high-performance sealing.

⚙️ Head Studs: OEM or Upgrade Options
For most builds, we recommend using your OEM head studs, or upgrading to the Kibblewhite heavy-duty head stud kit for maximum durability.
🔗 Click here for the Kibblewhite Stud Kit

⛽ Fuel Versatility
Piston is compatible with both pump and race fuel applications.

🔥 NGK Spark Plug Included
Pre-gapped and ready for install — no need to source one separately.

Compatibility:
✔️ Fits all model years of:

• Honda 400EX

• Honda 400X

• Honda XR400R

⚠️ Important Warranty Info:
This kit is not DIY-friendly — professional installation and tuning are required. Improper installation, poor break-in, or lack of maintenance will void all warranties. Warranty coverage requires parts be returned for inspection; no photos, emails, or third-party assessments will be accepted.