Get in there with some soapy water and some wet`n`dry paper and carefully rub the alloy off. The nicasil is rock hard, so unless you`re a real animal you wont damage it (any more than it is already!).
You`ll more than likely find that the plating underneath is OK. It often is. What usually kills them is when a ring breaks up, or a circlip comes out, and a bit of steel makes its way between the piston and the bore and scores through the plating. When it's just molten alloy between the piston and cylinder wall, it`s usually salvageable.
Anyway, it`s off now, and you`ve got nothing to loose by getting in there with the 800 grit! Just go slowly and carefully!
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There`s no cure for stupidity… but with the endless supply of stupid people around me, I must be close to finding it!
The Lizard tells it like it is!
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Vampire?