WOSSNER piston kit for KTM SX-F 250, XC-F 250, GAS GAS MC 250 F and HUSQVARNA FC 250 from 2023 to 2027

WOSSNER offers this piston kit for KTM SX-F 250, XC-F 250, GAS GAS MC 250 F and HUSQVARNA FC 250 from 2023 to 2027. The piston slides in the cylinder and takes the force of the air-fuel combustion, passing it to the connecting rod and crankshaft.

Why choose a forged piston?

Instead of simply being cast, a forged piston is hot-pressed under very high pressure and then machined: its metal is denser and free of air pockets.

• Stronger when hot: it copes better with high revs, overheating and detonation.
• Lighter for the same strength: less stress on the connecting rod and bearings.
• Good to know: depending on the alloy, it expands a little more and is fitted with more clearance; slight noise when cold is normal.
• Why does it cost more? Forging tools, full machining and surface treatments cost more than simple casting.

Why choose WOSSNER?

Wössner has forged its own pistons since 1994: Molykote-coated skirt to reduce friction and ease running-in, kit supplied complete with rings, pin and clips.

When should you replace the piston?

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

Recommended hours for a top-end rebuild (manufacturer recommendation for the KTM SX-F, Husqvarna FC, GASGAS MC-F since 2023):

• Racing: every 45 h.
• Leisure: no KTM figure; Cross-Mania guideline: compression check at around 90 h.

Specifications and fitting tips

• Contents: Piston #4090DA, Ring Set #RIK81.00A/2, Wrist Pin #WP070DLC, Retaining Clips #CW16
• Bore: 81.00 mm
• Oversize: Standard
• Displacement: 250 cm³
• Stroke: 48.50 mm
• Piston material: Aluminium alloy, Forged
• Machining optimised for low weight while keeping strength in key areas such as the crown and skirt

Cross-Mania tip: Measure the cylinder bore before ordering: the piston must match your cylinder size. Follow the manufacturer's break-in procedure and replace the top-end gaskets at the same time.

Also needed with this part

• Top-end gasket kit : MOOSE 810328MSE · MOOSE 819037MSE
• Spark plug : NGK 2305 · NGK 97225
• 4-stroke engine oil : LIQUI MOLY 10W40 1 L · MOTUL 10W50
• Air filter : HIFLO FILTRO · TECNIUM

Compatibility

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

Fits:
GAS GAS MC 250 F 2027
GAS GAS MC 250 F 2026
GAS GAS MC 250 F 2025
GAS GAS MC 250 F 2024
HUSQVARNA FC 250 2026
HUSQVARNA FC 250 2025
HUSQVARNA FC 250 2024
HUSQVARNA FC 250 2023
KTM SX-F 250 2027
KTM SX-F 250 2026
KTM SX-F 250 2025
KTM SX-F 250 2024
KTM SX-F 250 2023
KTM XC-F 250 I 2027
KTM XC-F 250 I 2026
KTM XC-F 250 I 2025
KTM XC-F 250 I 2024
KTM XC-F 250 I 2023