ATHENA Cylinder Base Gasket for KTM EGS 125, EXC 125, GS 125, MX 125, SX 125 1984-1986

ATHENA offers this cylinder base gasket for KTM EGS 125, EXC 125, GS 125, MX 125, SX 125 1984-1986. 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 EGS 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: S410270006021 (0.05 mm), S410270006020 (0.20 mm), S410270006019 (0.40 mm), S410270006018 (0.50 mm), S410270006017 (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 24419A · VERTEX 24243A
• Piston rings : PROX · VERTEX
• 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 1986
KTM EGS 125 1985
KTM EGS 125 1984
KTM EXC 125 1986
KTM EXC 125 1985
KTM EXC 125 1984
KTM GS 125 1986
KTM GS 125 1985
KTM GS 125 1984
KTM MX 125 1986
KTM MX 125 1985
KTM MX 125 1984
KTM SX 125 1986
KTM SX 125 1985
KTM SX 125 1984