ATHENA Racing Forged Piston for ATHENA cylinder for KTM EXCF 250, SXF 250, XCF 250 and HUSQVARNA FC 250, FE 250 2013-2022

The ATHENA Racing forged piston (Ø 81.95 to 81.96 mm depending on the size class) is designed for KTM EXCF 250, SXF 250, XCF 250 and HUSQVARNA FC 250, FE 250 from 2013 to 2022. 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 numbers: S4F08200005A, S4F08200005B
• Engine: 4-stroke
• For ATHENA cylinder kit ref. P400270100023 (Ø82 mm)
• Piston diameter: A = 81.95 mm, B = 81.96 mm
• Available versions: A: ref. S4F08200005A; B: ref. S4F08200005B
• Weight: 270 g

Choosing the right size class

The letters A, B, C… are very close diameter grades, one hundredth of a millimetre apart. Measure the cylinder bore with a bore gauge (diameter, ovality and taper) and choose the grade that gives the piston-to-cylinder clearance specified by the manufacturer. As a rule, grade A goes into a new or reconditioned cylinder, grade B into a cylinder that has already been run in. A scored or out-of-spec cylinder has to be reconditioned: you don't make up for its wear with a bigger grade.

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

• ATHENA cylinder kit : ATHENA
• Piston rings : ATHENA
• Top end gasket kit : ATHENA
• Spark plug : NGK 3521 · NGK 97225
• 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.

Which size should I order?
Measure your cylinder: A, B correspond to different actual diameters (81.95 to 81.96 mm). Choose the class that gives the piston-to-cylinder clearance specified by the manufacturer.

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:
HUSQVARNA FC 250 2022
HUSQVARNA FC 250 2021
HUSQVARNA FC 250 2020
HUSQVARNA FC 250 2019
HUSQVARNA FC 250 2018
HUSQVARNA FC 250 2017
HUSQVARNA FC 250 2016
HUSQVARNA FE 250 2019
HUSQVARNA FE 250 2018
HUSQVARNA FE 250 2017
HUSQVARNA FE 250 2016
KTM EXCF 250 2019
KTM EXCF 250 2018
KTM EXCF 250 2017
KTM EXCF 250 2016
KTM EXCF 250 2015
KTM EXCF 250 2014
KTM SXF 250 2022
KTM SXF 250 2021
KTM SXF 250 2020
KTM SXF 250 2019
KTM SXF 250 2018
KTM SXF 250 2017
KTM SXF 250 2016
KTM SXF 250 2015
KTM SXF 250 2014
KTM SXF 250 2013
KTM XCF 250 2022
KTM XCF 250 2021
KTM XCF 250 2020
KTM XCF 250 2019
KTM XCF 250 2018
KTM XCF 250 2017
KTM XCF 250 2016