ATHENA Cast Piston for KTM, HUSQVARNA, GAS GAS, BETA and HUSABERG 2005-2025

Name: ATHENA Cast Piston for KTM, HUSQVARNA, GAS GAS, BETA and HUSABERG 2005-2025
Brand: ATHENA
SKU: S4C06640001
Price: 136.9 EUR
Availability: BackOrder

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€136.90

Tax Included

Disponible en nuestro proveedor, enviado en 10 a 15 días.

ATHENA cast piston Ø 66.34 to 66.37 mm depending on the size class for KTM EXC, FREERIDE, SX, XC, XCW 250, GAS GAS EC, EX, MC 250, HUSQVARNA TC, TE 250, BETA RR 250 and HUSABERG TE 250 from 2005 to 2025. Available in A, B, C, D.

The ATHENA cast piston (Ø 66.34 to 66.37 mm depending on the size class) is designed for KTM EXC 250, FREERIDE 250, SX 250, XC 250, XCW 250, GAS GAS EC 250, EX 250, MC 250, HUSQVARNA TC 250, TE 250, BETA RR 250 and HUSABERG TE 250 from 2005 to 2025. A cast piston is made by pouring molten aluminium into a mould. It expands a little less than a forged piston: the engine runs with a tighter piston-to-cylinder clearance and is quieter when cold. It's the right choice for leisure or enduro riding, with regular maintenance.

Specifications

Brand: ATHENA
Manufacturer part numbers: S4C06640001A, S4C06640001B, S4C06640001C, S4C06640001D
Engine: 2-stroke
Piston diameter: A = 66.34 mm, B = 66.35 mm, C = 66.36 mm, D = 66.37 mm
Available versions: A: ref. S4C06640001A; B: ref. S4C06640001B; C: ref. S4C06640001C; D: ref. S4C06640001D

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.

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 20 to 40 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

Clean the cylinder and check it: diameter, ovality, taper and condition of the bore coating.
Check the end gap of each ring in the cylinder against the figures in the manual or the manufacturer's instructions.
Fit the rings with the mark facing up and each gap correctly located on its locating pin.
Check the small-end needle bearing and the pin: at the slightest play, tight spot or marked needle, replace the bearing.
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.
Reassemble with a new top end gasket kit and tighten the cylinder head in a criss-cross pattern to the manufacturer's torque.
Refill the coolant and fit a new spark plug.
Break the engine in: warm it up gently, vary the revs and avoid sustained full throttle for the first hour.

Why ATHENA?

Athena, an Italian company founded in 1973 near Vicenza, designs gaskets, pistons and cylinder kits for motorcycles. An OEM supplier to KTM, Ducati, Fantic, Piaggio and Triumph and a partner of the MXGP world championship, it develops its parts on the test bench and on the track with racing teams.

Spare parts and items to plan

Piston rings : WOSSNER · VERTEX
Piston pin : WOSSNER CW18 · WOSSNER WP033
Piston pin clips : WISECO · VERTEX
Top-end gasket kit : ATHENA M752007300094 · ATHENA M752010500094
Small end needle bearing : PROX · ATHENA
Spark plug : NGK 3520 · NGK 6664
Coolant : LIQUI MOLY 1 L · TWIN AIR
2-stroke oil : LIQUI MOLY 1 L 3065 · LIQUI MOLY 1 L 3063

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, C, D correspond to different actual diameters (66.34 to 66.37 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.

Should I replace the small-end needle bearing?
It isn't included. Check it at every piston change and replace the needle bearing at the slightest play or tight spot.

Compatibility

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

Reference S4C06640001A

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Specific References

Click on your bike to see all compatible parts.

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ATHENA Cast Piston for KTM, HUSQVARNA, GAS GAS, BETA and HUSABERG 2005-2025

€136.90

Tax Included


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ATHENA Cast Piston for KTM, HUSQVARNA, GAS GAS, BETA and HUSABERG 2005-2025

Specifications

Choosing the right size class

When to replace it?

Fitting tips

Why ATHENA?

Spare parts and items to plan

Frequently asked questions

Compatibility

ATHENA Cast Piston for KTM, HUSQVARNA, GAS GAS, BETA and HUSABERG 2005-2025