ATHENA Cylinder Base Gasket for KTM EGS 125, EXC 125, GS 125, MX 125, SX 125 1987-1997

ATHENA offers this cylinder base gasket for KTM EGS 125, EXC 125, GS 125, MX 125, SX 125 1987-1997. 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 GS 125?

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: S410270006026 (0.05 mm), S410270006025 (0.20 mm), S410270006024 (0.30 mm), S410270006023 (0.50 mm), S410270006022 (0.75 mm), S410270006043 (1 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 · CENTAURO
• Piston : VERTEX 24243A · VERTEX 24419A
• Piston rings : VERTEX · WISECO
• 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 EGS 125 1997
KTM EGS 125 1996
KTM EGS 125 1995
KTM EXC 125 1997
KTM EXC 125 1996
KTM EXC 125 1995
KTM GS 125 1994
KTM GS 125 1993
KTM GS 125 1992
KTM GS 125 1991
KTM GS 125 1990
KTM GS 125 1989
KTM GS 125 1988
KTM GS 125 1987
KTM MX 125 1994
KTM MX 125 1993
KTM MX 125 1992
KTM MX 125 1991
KTM MX 125 1990
KTM MX 125 1989
KTM MX 125 1988
KTM MX 125 1987
KTM SX 125 1997
KTM SX 125 1996
KTM SX 125 1995