ATHENA Racing Forged Piston for YAMAHA WRF 250, YZF 250 and GAS GAS ECF 250 2001-2015

On YAMAHA WRF 250, YZF 250 and GAS GAS ECF 250 from 2001 to 2015, the ATHENA Racing S4F079000010 forged piston (Ø 78.96 mm) fits in place of the original part. The piston takes every combustion and passes it on to the connecting rod. Forged rather than cast, it stands up better to thermal shock and high revs: a real asset for an engine pushed hard in racing or tuned.

Key features

• High-silicon aluminium alloy, forged by reverse extrusion.
• CNC machined to a tolerance of less than 0.01 mm, tested on the bench and on the track.
• Rings made in Japan, with a PVD or chromium nitride coating.
• Supplied with pin, circlips and ring(s).

Specifications

• Brand: ATHENA
• Manufacturer part number: S4F079000010
• EAN code: 8050444894286
• Engine: 4-stroke
• Piston diameter: 78.96 mm
• Weight: 270 g

When to replace it?

• Loss of power, sluggish pick-up, harder starting: compression is dropping.
• Piston slap on a cold engine, getting more and more noticeable.
• On teardown: vertical scoring on the skirt, stuck or worn rings, thick carbon on the crown.
• On a four-stroke: oil consumption, blue smoke and a fouled spark plug.

Replace the piston as set out in your bike's service manual, sooner if you race, and straight away as soon as these symptoms appear. As a Cross-Mania guideline, plan for a new piston every 30 to 60 hours of engine running depending on whether you race or ride for fun. Always measure the cylinder at the same time: a new piston in an oval cylinder won't last.

Fitting tips

1. Clean the cylinder and check it: diameter, ovality, taper and condition of the bore coating.
2. Check the end gap of each ring in the cylinder against the figures in the manual or the manufacturer's instructions.
3. Fit the rings with the mark facing up and the gaps staggered, never letting the ends of the oil control ring overlap.
4. Fit the piston with its arrow pointing to the exhaust side, oil the pin and the small end, then fit the circlips without distorting them, gap opposite the notch. A circlip that has been taken out is replaced with new piston pin circlips, never refitted.
5. Reassemble with a new top end gasket kit and tighten the cylinder head in a criss-cross pattern to the manufacturer's torque.
6. Refill the coolant, fit a new spark plug and change the oil with fresh engine oil and a new filter.
7. Break the engine in: warm it up gently, vary the revs and avoid sustained full throttle for the first hour.

Why ATHENA?

Founded in 1973 near Vicenza, Athena is an Italian engine gasket specialist that has made its gaskets on its own production lines since day one, as well as a renowned manufacturer of pistons and cylinder kits. The brand supplies original equipment to manufacturers such as KTM, Ducati, Fantic, Piaggio and Triumph, and is a partner of the MXGP motocross world championship.

Spare parts and items to plan

• Piston rings : VERTEX · ATHENA
• Piston pin : ATHENA
• Piston pin clips : WISECO · VERTEX
• Top-end gasket kit : MOOSE · CENTAURO
• Spark plug : NGK 3521 · NGK 4218
• Coolant : LIQUI MOLY 1 L · TWIN AIR
• 4-stroke engine oil : LIQUI MOLY 10W40 1 L · MOTUL 10W50

Frequently asked questions

Does the piston come complete?
Yes: piston, pin, circlips and ring(s). The top end gasket kit has to be ordered separately, because a head or base gasket can never be reused.

Can I replace just the rings later?
Yes, as long as the piston and cylinder are still within tolerance. Replacement rings can be ordered on their own, as can the piston pin and the circlips.

Compatibility

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

Fits:
GAS GAS ECF 250 2015
GAS GAS ECF 250 2014
GAS GAS ECF 250 2013
GAS GAS ECF 250 2012
GAS GAS ECF 250 2011
GAS GAS ECF 250 2010
YAMAHA WRF 250 2013
YAMAHA WRF 250 2012
YAMAHA WRF 250 2011
YAMAHA WRF 250 2010
YAMAHA WRF 250 2009
YAMAHA WRF 250 2008
YAMAHA WRF 250 2007
YAMAHA WRF 250 2006
YAMAHA WRF 250 2005
YAMAHA WRF 250 2004
YAMAHA WRF 250 2003
YAMAHA WRF 250 2002
YAMAHA WRF 250 2001
YAMAHA YZF 250 2007
YAMAHA YZF 250 2006
YAMAHA YZF 250 2005
YAMAHA YZF 250 2004
YAMAHA YZF 250 2003
YAMAHA YZF 250 2002
YAMAHA YZF 250 2001