ATHENA Cylinder Base Gasket for APRILIA MX 125, RX 125 and KTM SX 125 1984-2006

On APRILIA MX 125, RX 125 and KTM SX 125 from 1984 to 2006, the ATHENA cylinder base gasket fits in place of the original part. Fitted under the cylinder, the base gasket is more than just a seal: its thickness sets the height of the cylinder, and with it the engine's squish and compression.

Key features

• Several thicknesses available for the same bike.
• The right tool for setting squish, compression and timing, according to Athena.

Specifications

• Brand: ATHENA
• Manufacturer part numbers: S410010006010, S410010006020
• Available versions: OE: ref. S410010006010; 0.40 mm: ref. S410010006020
• Weight: 50 g
• Engine: 2-stroke

Choosing the right thickness

Measure the thickness of the old gasket with a vernier caliper and fit the same, unless you are deliberately adjusting the squish. A thicker gasket increases the squish and lowers compression; a thinner one does the opposite. After any change of thickness, check the squish with solder wire.

When to replace it?

• Oil or coolant seeping at the base of the cylinder.
• Gasket crushed or torn on removal.

Every time the cylinder is removed: a crushed base gasket can't be reused.

Fitting tips

1. Clean the crankcase face and the base of the cylinder without scratching them.
2. Fit the gasket dry, centred on the studs.
3. Tighten the cylinder in a criss-cross pattern to the manufacturer's torque.
4. If you have changed the thickness, measure the squish before refitting the cylinder head with a new head gasket.

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

• Top-end gasket kit : see the selection
• Piston rings : PROX · VERTEX
• Coolant : LIQUI MOLY 1 L · TWIN AIR

Frequently asked questions

Which thickness should I choose?
The same as your original gasket, unless you are deliberately adjusting the squish. Thicknesses available: OE, 0.40 mm.

Should the other gaskets be replaced?
Yes, as soon as the cylinder is removed: a top end gasket kit includes all the gaskets that need replacing.

Compatibility

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

Fits:
APRILIA MX 125 2006
APRILIA MX 125 2005
APRILIA MX 125 2004
APRILIA RX 125 1999
APRILIA RX 125 1998
APRILIA RX 125 1997
APRILIA RX 125 1996
APRILIA RX 125 1995
KTM SX 125 1986
KTM SX 125 1985
KTM SX 125 1984