I finally got around to overhauling the BB on my Grand Jubilé yesterday. After cleaning, I noticed some corrosion marks on the both cups. The drive side grease was still in good condition, the NDS grease was black and sticky, like glue, and there was little or none in the bearing. Here is a photo of the corrosion. Since it wasn't exhibiting any symptoms when riding, I went ahead and reassembled the BB with fresh grease. Based the appearance of the cup, should I be looking for a replacement cup or complete BB?
Related question, I'm not schooled in identifying the thread types, since everything else on the bike seems to be English threaded, I assume the BB is also, can anyone tell from the second photo - it does clearly show that the threads on the two cups are opposite? It is a Sakae, BTW. Thanks for any assistance!

Don't you remember which direction you turned the fixed cup to get it out?
Based on the 2nd photo, yes it looks like the fixed cup has LH threads, which could be BSC but since it's a Moto you can't rule out Swiss. Given it's a Sakae I'd be surprised if it was Swiss, however. Are there no numbers stamped on the cups? How do the spindle bearing surfaces look (these usually wear faster than the cups do)?
I'd say it's hard to give a diagnosis based on that one photo, but the cup looks to have a bit of corrosion/pitting so I'd start getting some replacement parts lined up...if it's BSC you will have tons of replacements to choose from, so...

Thanks for the input. I didn't notice any pitting or wear on the balls or the spindle. I will get confirmation of the threading, then look around for replacement parts.
The bike spent the majority of the past 30 years stored in various garages & sheds, rather than being ridden regularly. I assume the corrosion is due to moisture condensing in the frame, then accumulating in the BB and sitting undisturbed for a long time.
Any recommendations other than a vintage replacement - e.g. sealed BB - & where to get?

That doesn't look all that bad to me. Run your finger nail over the discolored areas; if there's no raised surface or if it's slight, you're fine. Use some 0000 steel wool to restore the uniformity of the curvature, make sure all residue is rinsed or wiped away. Wouldn't hurt to finish off with a bit of metal polish.

As long as the hardened bearing surface is not compromised and true circularity in intact in all planes you should be OK.

I've done this on multiple occasions. No need to contemplate discarding a BB unless you have more severe evidence than this. On the other hand I agree that the Sakae is unlikely to be Swiss (or French), may not be original and may not be all that expensive to replace.

J

Thanks alfilado. As stated above I've reassembled the BB and put back into (limited) use in the condition shown. But I'm planning on laying the Moto up for a complete overhaul sometime this summer, so I'll have another go at it and follow your recommendations.
My engineering gut was telling me this isn't too serious, since there is no metal fatigue or galling; and I assume any corrosion that raised above the surface quickly spalled off and combined with the grease as the bearings rolled over.

The steel wool is probably quite adequate to clean of the corrosion. I prefer a wadded up piece of aluminum foil. The wad of foil will clean of any corrosion and help to smooth the race. Clean carefully after and then, using a ball point pen, trace the ball bearing path and "feel for tiny pits". If there are no pits, replace the balls and keep your bottom bracket.

I hope this is a help.

I think you just have stained cup. Clean it real good with scrubby pad/steel wool and soapy water and you should be good.

agreed, and that's my preferred cleaning method as well. lots of dish soap and some #0 steel wool should do the trick.

Along with SAKAE MADE IN JAPAN the cups are inscribed 35XPI. Does that tell anyone anything? I did some searching on the web and didn't come up with any positive information.

Thanks everyone for the cleaning tips. I'll have a go next time I take it apart.

Swiss threads, too bad as you're not going to find many replacements, but keep the ones you have in good shape...first I've heard of Sakae making Swiss BBs!

Yeah, after some more searching I came to the conclusion that the threads are Swiss...
I'll be sure to take good care of the BB from here on out!
I found that Phil Wood has stainless steel replacement cups for about $47 (didn't notice any gold plating though). Nice to know for a contingency plan.

That's just for the cups, you'll still need a Phil BB or UN-72, etc to fit inside the cups....

Yikes! So the bearing race diameters and ball diameters aren't standardized then, I take it?

Yep Swiss threads on the Grand Jubille. I had mine reamed and re-tappad to Italian, but I have always been sorry I did.

By the way, those cups are in good condition. Just a little staining. No worries on thirty year old cups.Clean 'em up, put in new bearings, and use 'em.