I am Restoring a comet and have, after much effort nice and clean crankcases, cylinder and head. Is there a finish to keep them in this condition and looking original?
If your talking about corrosion ?
Don't ride it in winter or the wet. Keep in a dehumidified garage.
Any clear coating I've ever tried does not work. Eventually , small wounds are inflicted by stones and road debris , then moisture will wick underneath and corrosion will commence worse than if uncoated.
There is a semi drying spray that can be applied to engine casings that will prevent corrosion , I think it was developed for Navy jet fighters on carriers at sea , but it needs to be cleaned off and reapplied at intervals.