ATHENA Cylinder Base Gasket for KTM GS 250, MX 250 1974-1979

The ATHENA cylinder base gasket is designed for KTM GS 250, MX 250 from 1974 to 1979. The base gasket seals between the cylinder and the crankcase. Its thickness matters: it sets the height of the cylinder, and therefore the squish, the compression and, on a two-stroke, the port timing.

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: S410270006009, S410270006010, S410270006011, S410270006012
• Available versions: 0.20 mm: ref. S410270006009; 0.30 mm: ref. S410270006010; 0.50 mm: ref. S410270006011; 1 mm: ref. S410270006012
• 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?

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

• Top-end gasket kit : INNTECK · ATHENA
• Piston : ATHENA S4F06750001 · ATHENA S4F068500010
• Piston rings : 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: 0.20 mm, 0.30 mm, 0.50 mm, 1 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:
KTM GS 250 1979
KTM GS 250 1978
KTM GS 250 1977
KTM GS 250 1976
KTM GS 250 1975
KTM GS 250 1974
KTM MX 250 1979
KTM MX 250 1978
KTM MX 250 1977
KTM MX 250 1976
KTM MX 250 1975
KTM MX 250 1974