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[Eydreeyun]

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[dude8383]

Usually a bit of wet sanding paper will remove that surface rust. If its really badly pitted I'd replace it for piece of mind

[AndrewBird]

I retract my previous statement. Was thinking the seal as on the piston, not in the bore. The groove on the piston retains the dust boot. I'd clean everything up with a wire wheel on the very rusty parts and call it good. Take some scotch brite to the piston where there is light rust to clean them up.