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I've found the correct o-rings for the cylinder in the sprocket cover for the Mille.
Order EPDM O-rings.
31.34mm X 3.53mm for the lower one.
31.42mm X 2.62mm for the upper one.

Seems to work ok.

Hope that it works for all MILLE owners.



The piston diameter is 30.97mm.


I've now measured the clutch cylinder.
The lower groove is 37.0mm outer diameter.
The upper groove is 35.55mm outer diameter.

The lower groove is 11.3 mm down (the upper side of the groove)
The upper groove is 3.3 mm down (the upper side of the groove)

These seals can be bought here..............
https://www.eur-o-rings.com/search/?q=3 ... D0CX5ySWS8


https://www.eur-o-rings.com/search/?q=3 ... 699bCry6HU

My friend helped me with the dimensions......I.e 35.55-30.97=4.58mm
4.58 /2=2.29mm
2.29+20%=2.75mm maximum size of o-ring,
37 - 30,97 = 6.03
6.03 / 2 = 3,015
3.015 + 20% = 3.618 maximum size of o-ring Max komprimering means Maximum compressing in Swedish

Ai overview: The correct hardness for the clutch slave cylinder piston O-rings housed inside the bore of a vintage Ducati Mille (as well as related Bevel square-case models like the S2 and MHR) is 70 Shore A.When sourcing replacements for this specific dynamic application, ensure they meet the following critical specifications:Material: EPDM (Ethylene Propylene Diene Monomer). Do not use Nitrile (Buna-N) or standard Viton, as they are chemically incompatible with DOT 3, DOT 4, or DOT 5.1 brake fluids and will quickly swell and degrade.Hardness: 70 Durometer (Shore A). Avoid harder 90 Shore A rings, as they will cause an excessively stiff clutch lever pull and fail to conform properly to the aged cylinder bore.Dimensions (for the factory 2-groove Mille casing):Lower O-ring: 31.34 mm x 3.53 mmUpper O-ring: 31.42 mm x 2.62 mm.