1974 XS/TX650 rebuild

[NeiljohnUK]

Interesting issue with the side case polishing, granularity from a cold spot during casting perhaps?

I have a fellow BMW boxer owner nearby who polished his engine (R80 sand cast casings) over a winter, had to repolish annually. Though the Ariel Red Hunter owner I met who did the same went so far the casings became porous and wept engine oil, ended up having to paint the inside with epoxy which stopped it to a degree, but as the metal was full of oil it didn't stick too well in some places. Modern water based engine paint is rubbish, my F800 has corrosion under all over, starting at any sharp edge where it's thinnest it creeps until it flakes it off, coat regularly with ACF-50 now to stop it getting any worse!

[tonyfoale]

the Ariel Red Hunter owner I met who did the same went so far the casings became porous and wept engine oil,

They didn't become porous they started life that way. It was a legal requirement for Brit bikes of that era to leak oil.