ATHENA Cylinder Base Gasket for KTM GS 350, GS 500, MX 350, MX 500, SX 440, SX 500, SX 540 1986-1996

The ATHENA cylinder base gasket is designed for KTM GS 350, GS 500, MX 350, MX 500, SX 440, SX 500, SX 540 from 1986 to 1996. 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: S410270006040, S410270006039, S410270006038
• Available versions: 0.20 mm: ref. S410270006040; 0.30 mm: ref. S410270006039; 0.50 mm: ref. S410270006038
• Weight: 50 g

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 : ATHENA P400270600070 · ATHENA S410270001010
• Piston : see the selection
• Piston rings : see the selection
• 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.

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 350 1994
KTM GS 350 1993
KTM GS 350 1992
KTM GS 350 1991
KTM GS 350 1990
KTM GS 350 1989
KTM GS 350 1988
KTM GS 350 1987
KTM GS 350 1986
KTM GS 500 1994
KTM GS 500 1993
KTM GS 500 1992
KTM GS 500 1991
KTM GS 500 1990
KTM GS 500 1989
KTM GS 500 1988
KTM GS 500 1987
KTM GS 500 1986
KTM MX 350 1994
KTM MX 350 1993
KTM MX 350 1992
KTM MX 350 1991
KTM MX 350 1990
KTM MX 350 1989
KTM MX 350 1988
KTM MX 350 1987
KTM MX 350 1986
KTM MX 500 1994
KTM MX 500 1993
KTM MX 500 1992
KTM MX 500 1991
KTM MX 500 1990
KTM MX 500 1989
KTM MX 500 1988
KTM MX 500 1987
KTM MX 500 1986
KTM SX 440 1994
KTM SX 440 1993
KTM SX 440 1992
KTM SX 440 1991
KTM SX 440 1990
KTM SX 440 1989
KTM SX 440 1988
KTM SX 440 1987
KTM SX 440 1986
KTM SX 500 1996
KTM SX 500 1995
KTM SX 500 1994
KTM SX 500 1993
KTM SX 500 1992
KTM SX 500 1991
KTM SX 500 1990
KTM SX 500 1989
KTM SX 500 1988
KTM SX 500 1987
KTM SX 500 1986
KTM SX 540 1994
KTM SX 540 1993
KTM SX 540 1992
KTM SX 540 1991
KTM SX 540 1990
KTM SX 540 1989
KTM SX 540 1988
KTM SX 540 1987
KTM SX 540 1986