PISTON KIT 40mm 81-21 YAMAHA PW50 18U-11631-00-A0 18U-11631-00-A0

This piston kit is a standard replacement designed for the Yamaha PW50 and various Yamaha 50cc models from 1979 to 2021. It provides precise fitment and durability for small two-stroke engines, matching or exceeding OEM specifications.

Features

• Constructed from high-tech materials for long-lasting performance and reliability

• Elliptically designed for consistent bearing surface under thermal expansion

• Direct OEM replacement for easy installation

• Includes all necessary components for complete piston replacement

• Manufactured to meet or exceed OEM quality standards

Specifications

• Piston Diameter: 40mm

• Piston Height: 50mm

• Piston Pin Length: 33mm (1.29″)

• Piston Pin Outer Diameter: 10mm

Package Included

• 1 x Piston

• 2 x Piston Rings

• 1 x Piston Pin

• 1 x Small End Bearing

• 2 x Circlips

Cross-Reference OEM Part Numbers

• PROX 01.2005.000

• Piston (Std): 18U-11631-00-A0, 4J2-11631-00-A0

• Piston Pin: 3L5-11633-00-00

• Piston Ring Set (Std): 260-11610-04-00, 260-11601-03-00

• Circlip: 93450-11021-00

Vehicle Fitments

• Yamaha PW50 (1981–2021)

• 1982 MJ50J

• 1979 QT50F

• 1980 LC50G

• 1980 QT50, QT502G, QT50G

• 1981 PW50H, QT50H

• 1982 PW50J, QT50J

• 1983 PW50K, QT50K

• 1984 YAMAHOPPER (QT50L)

• 1985 Y-ZINGER (PW50N), YAMAHOPPER (QT50N)

• 1986 Y-ZINGER (PW50S), YAMAHOPPER (QT50S)

• 1987 Y-ZINGER (PW50T), YAMAHOPPER (QT50T)

• 1990–2021 Y-ZINGER / PW50 (PW50A to PW50M2, including all suffix variants)