ATHENA Cast Piston lightweight Racing for YAMAHA WR 125, YZ 125 and FANTIC XE 125, XX 125 2005-2026

ATHENA offers this piston kit for YAMAHA WR 125, YZ 125 and FANTIC XE 125, XX 125 2005-2026. The piston slides in the cylinder and takes the force of the air-fuel combustion, passing it to the connecting rod and crankshaft.

Why a cast piston?

A cast piston is moulded from a high-silicon aluminium alloy, then machined.

• Low expansion: it runs with a tight clearance, stays quiet when cold and warms up quickly.
• Durability: an excellent choice for a stock engine used for leisure or enduro.
• Price: more affordable than a forged piston.
• Good to know: it copes less well with overheating and extreme revs than a forged one.

Why choose ATHENA?

Athena, the Italian manufacturer founded in 1973, is an original-equipment supplier to manufacturers such as KTM and Ducati: the same standards for your replacement parts.

When should you replace the piston on your YAMAHA YZ 125?

Harder starting, loss of power, blue smoke, oil consumption or a knock when cold: these are the signs of a tired top end.

No manufacturer hour figure for this model. Cross-Mania guideline: compression check every 20 h in hard use and every 40 h for leisure.

Specifications and fitting tips

• Engine: 2-stroke
• Manufacturer part numbers: S4C05400025A (A), S4C05400025B (B), S4C05400025C (C), S4C05400025D (D)

Available in several sizes: choose the one that matches your cylinder (stamped size or measured bore). Diameters: A = 53.94 mm, B = 53.95 mm, C = 53.96 mm, D = 53.97 mm.

Spare parts and items to plan

• Piston rings : PROX · VERTEX
• Piston pin : VERTEX · WOSSNER
• Top-end gasket kit : ATHENA · ATHENA 150
• Small end needle bearing : HOT RODS · ATHENA
• Spark plug : NGK 3530 · NGK 3230
• Coolant : LIQUI MOLY 1 L · TWIN AIR
• 2-stroke oil : LIQUI MOLY 1 L · MOTUL 800 1 L

Compatibility

Check the exact model and year of your bike in the list below before ordering.

Fits:
FANTIC XE 125 2025
FANTIC XE 125 2024
FANTIC XE 125 2023
FANTIC XE 125 2022
FANTIC XE 125 2021
FANTIC XX 125 2025
FANTIC XX 125 2024
FANTIC XX 125 2023
FANTIC XX 125 2022
FANTIC XX 125 2021
YAMAHA WR 125 2023
YAMAHA WR 125 2022
YAMAHA WR 125 2021
YAMAHA WR 125 2020
YAMAHA WR 125 2019
YAMAHA WR 125 2018
YAMAHA WR 125 2017
YAMAHA WR 125 2016
YAMAHA WR 125 2015
YAMAHA WR 125 2014
YAMAHA WR 125 2013
YAMAHA WR 125 2012
YAMAHA WR 125 2011
YAMAHA WR 125 2010
YAMAHA WR 125 2009
YAMAHA WR 125 2008
YAMAHA WR 125 2007
YAMAHA WR 125 2006
YAMAHA WR 125 2005
YAMAHA YZ 125 2026
YAMAHA YZ 125 2025
YAMAHA YZ 125 2024
YAMAHA YZ 125 2023
YAMAHA YZ 125 2022
YAMAHA YZ 125 2021
YAMAHA YZ 125 2020
YAMAHA YZ 125 2019
YAMAHA YZ 125 2018
YAMAHA YZ 125 2017
YAMAHA YZ 125 2016
YAMAHA YZ 125 2015
YAMAHA YZ 125 2014
YAMAHA YZ 125 2013
YAMAHA YZ 125 2012
YAMAHA YZ 125 2011
YAMAHA YZ 125 2010
YAMAHA YZ 125 2009
YAMAHA YZ 125 2008
YAMAHA YZ 125 2007
YAMAHA YZ 125 2006
YAMAHA YZ 125 2005