ATHENA Cylinder Head Insert for ATHENA cylinder kit for FANTIC XE 125, XX 125 and YAMAHA YZ 125 2022-2026

The ATHENA S410485308048 cylinder head insert is designed for FANTIC XE 125, XX 125 and YAMAHA YZ 125 from 2022 to 2026. The insert forms the combustion chamber of the VHM head. Its volume sets the engine's compression: a small volume gives more bottom end and mid-range, a larger volume keeps the engine smoother and longer-revving.

Specifications

• Brand: ATHENA
• Manufacturer part number: S410485308048
• EAN code: 8051757054282
• For ATHENA cylinder kit ref. P400485100102
• Weight: 120 g
• Engine: 2-stroke

When to change the insert?

• Switch to a different fuel (98 or race fuel with a higher octane rating).
• Engine knocking (pinking) or running hot: compression too high for the fuel.
• You want more torque on tight or sandy terrain.

Change the insert when you change fuel or type of riding, or if the engine pinks. The insert's three dimensions (volume, piston height, squish) must match your engine.

Fitting tips

1. The insert is changed with the cylinder head removed.
2. Check that the actual height of your piston at top dead centre matches the figure given for the insert.
3. Replace the VHM head O-rings every time you take it apart.
4. Check the squish with solder wire before riding.
5. Tighten the head to the recommended torque, in a criss-cross pattern and in several stages, then fit a new spark plug.

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 : ATHENA
• Top end gasket kit : ATHENA
• Exhaust power valve parts : ATHENA
• Cylinder kit bolt kit : ATHENA
• VHM head O-rings : see the selection
• Spark plug : NGK
• Coolant : LIQUI MOLY 1 L · TWIN AIR

Frequently asked questions

Will it fit my original cylinder head?
No: VHM inserts only fit VHM cylinder heads.

Which version should I choose?
Choose according to your engine and fuel.

Compatibility

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

Fits:
FANTIC XE 125 2024
FANTIC XE 125 2023
FANTIC XX 125 2025
FANTIC XX 125 2024
FANTIC XX 125 2023
FANTIC XX 125 2022
YAMAHA YZ 125 2026
YAMAHA YZ 125 2025
YAMAHA YZ 125 2024
YAMAHA YZ 125 2023
YAMAHA YZ 125 2022