What is this cog called?

[Athame57]

It might be the lighting, I can see what looks like quite a bit of light surface rust on the gearbox internals - mine was the same as was the gearbox output shaft where the front sprocket sits.

Not sure how quickly the surface rust returns or if there is any real danger of it contaminating the oil and reaching the crank journals - presumably the oil filter should catch that sort of stuff.

Maybe it has something to do with this engine now being open for more than two weeks?

[McCabe-Thiele (Ted)]

It could be imho the rust stains on that bearing in the right of the photo looks like moisture has been there quite a while.

More experienced members here will have seen worse - probably just normal on an old bike like ours even more so if not used over the winter with no oil splashing about.

Not forgetting that water emulsifies with mineral oil - less so with sythetic oil that we can't use as they put micronised chalk into modern oils to stop acid formation from burnt sulpher.

[Athame57]

Not forgetting that water emulsifies with mineral oil - less so with sythetic oil that we can't use as they put micronised chalk into modern oils to stop acid formation from burnt sulpher.

Maybe we should try a few hundred miles on White Vinegar/ Mineral Oil pre-mix?