Slow progress, but progress.
Despite heavy surface corrosion, I've reclaimed the ignition/front sprocket cover.
As per usual, I didn't bother taking 'before' photos, but here's a pic of the clutch cover to give you an idea.
They're die-cast aluminium, chromed from the factory. Over the years, moisture gets under the chrome, corroding the alloy underneath. On the bright side, this makes it easy to remove the chrome - just hit it with the bead blaster and most of it leaps off.
This is what the alloy looks like underneath (this is the auto-lube cover):
The remaining chrome is a bit more difficult though - hand filing takes too long, the wire-wheel is ineffective. I ended up using a very slow, very careful application of the linisher, and then hand filing/sanding.
Then I went over the whole thing with a fine hand file, removing the corrosion pitting. It wasn't so hard to remove the pitting, but the killer is that the file picks up bits of swarf and then they gouge a new scratch into the metal...
I've minimised the gouges, but it still needs a lot more work with the wet-and-dry paper. But I was getting impatient, so I gave it a quick hit with the buffing wheel, and that pleased me a lot:
There's about seven or eight hours work in the ignition cover alone, to this point.
It really needs another couple of hours being cleaned up with wet and dry, and then probably another hour polisihing it properly....
The worst bit is that the clutch cover is next, and its far more complex than the ignition cover... :'(