Piston Kit 75-81 DT400 MX 85.5, Wossner 8263D050 Yamaha

This Wossner piston kit features an 85.50mm bore size (85.42mm actual) and is designed for Yamaha DT400 (1975–1978) and MX410 (1975–1976) models. Manufactured in Germany, this forged piston is engineered for strength and thermal efficiency. The elliptical design supports even load distribution during expansion, reducing the risk of piston collapse by preventing localised pressure points.

Features

• Forged construction for increased strength

• Elliptical design ensures uniform load distribution under heat expansion

• Promotes efficient combustion chamber heat transfer to cylinder walls

• Made in Germany

Specifications

• Bore Size: 85.50mm (85.42mm)

• Display: 398 cm³

• Stroke: 70.00 mm

• Clearance: 0.08 mm

• Compression Height: 40.00 mm

• Compression Ratio: 2-stroke (Wossner and OEM)

Cross-Reference OEM Part Numbers

• Piston Kit: 8263D050

• Lock: CW18

• Pin: WP042

• Ring Set: RSC8550 x2

• Part No.: 56-W549_0.50.WO

Vehicle Fitments

• Yamaha DT400 1975

• Yamaha DT400 1976

• Yamaha DT400 1977

• Yamaha DT400 1978

• Yamaha MX410 1975

• Yamaha MX410 1976

• Yamaha DT Base 1979

• Yamaha DT Base 1980

• Yamaha DT Base 1981

• Yamaha MX 400 1975

• Yamaha MX 400 1976

• Yamaha MX 400 1977

• Yamaha MX 400 1978

• Yamaha MX 400 1979

• Yamaha MX 400 1980

• Yamaha MX 400 1981