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

ATHENA offers this cylinder base gasket for KTM GS 350, GS 500, MX 350, MX 500, SX 440, SX 500, SX 540 1986-1996. The base gasket sits under the cylinder, on the crankcase. Crushed when tightened, it cannot be reused: replace it every time the cylinder comes off.

Why does the thickness matter?

The benefits:

• The OE thickness keeps the cylinder height intended by the manufacturer.
• Another thickness lets you correct piston-to-head clearance after machining or adjust the port timing of a 2-stroke.
• A new gasket keeps the bottom end sealed against oil and gases.

Why choose ATHENA?

Athena, founded in 1973 by Giovanni Mancassola near Vicenza and based in Alonte (Italy), designs gaskets, pistons and cylinder kits; it supplies original equipment to manufacturers such as KTM, Ducati, Fantic and Triumph.

When should you replace the base gasket on your KTM SX 500?

Every time the cylinder comes off: piston change, top-end rebuild or cylinder inspection. Oil or mixture seeping at the base of the cylinder also points to a tired gasket.

No manufacturer figure in hours for this model. Cross-Mania guideline: compression check every 20 h of hard use and every 40 h of leisure riding.

Specifications and fitting tips

• Manufacturer part numbers: S410270006040 (0.20 mm), S410270006039 (0.30 mm), S410270006038 (0.50 mm)

Choose the thickness from the list. "OE" is the factory thickness; another thickness is used to set the cylinder height after a rebuild (piston-to-head clearance, port timing on a 2-stroke).

Cross-Mania tip: Choose the OE thickness if the cylinder and head have not been machined; if in doubt, measure the squish with solder wire before final assembly.

Spare parts and items to plan

• Top-end gasket kit : ATHENA S410270001010 · ATHENA P400270600070
• Piston : see the selection
• Piston rings : see the selection
• Coolant : LIQUI MOLY 1 L · TWIN AIR

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