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Reply to "Black stuff in clutch master reservoir"

The seal used in the stock type Pantera clutch master cylinder is a type of o-ring, not a "cup".  As such, the o-ring can only tolerate a very small interference fit to the master cylinder bore, something like 0.002".  Rebuilding the master cylinder by honing the bore and replacing the seal usually results in an early failure because the honing increases the cylinder's bore which reduces the interference fit with the o-ring.  

The fluid turning black is caused by extremely small amounts of material being removed from the o-ring  during normal cycling of the clutch master cylinder's piston.

John

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