Wössner forged piston kit with an 85.02mm bore, designed for Honda TRX400EX and TRX400X ATVs. Manufactured in Germany, this high-performance piston enhances strength, heat transfer, and durability. The elliptical design ensures uniform bearing surface distribution, reducing localized pressure and preventing piston collapse.

Features

• Forged construction for superior strength and durability


• Optimized heat transfer to cylinder walls


• Elliptical design for uniform bearing surface under heat expansion


• Increased compression ratio for improved engine performance


• Made in Germany

Specifications

• Bore: 85.02mm (84.96mm actual)


• Display: 397 cm³


• Stroke: 70.00mm


• Clearance: 0.06mm


• Wössner Compression Ratio: 12.50:1


• OEM Compression Ratio: 10.00:1


• Dome Volume: +8.40 cm³


• Compression Height: 26.20mm

Cross-Reference OEM Part Numbers

• Wössner Piston: 8702DC


• Lock: CW20


• Pin: WP052


• Ring Set: 850XSY


• Rod: P4021

Vehicle Fitments

• Honda TRX400EX (1999-2008)


• Honda TRX400X (2009-2012)