bottom bracket cups are cracked
 

I have the old school square tapered ones. I would need to buy cups. any idea who still sells them?

Tons of them at eBay, used and NOS, you will just need to find the correct threading and spindle size. Threading comes in JIS, French, Swiss, Italian, English (ISO). The cups and lock rings come in steel and aluminum. You also have a chice of sealed or loose bearing types. Best to go with sealed, of course, if you are looking for long term realiability and minimal maintenance. Don't bother with Titanium for these parts as they are just expensive weight weenie bling that might crack on you if you really work them hard.

Chombi

Have you removed them yet? Sometimes they are difficult to remove and trash the threads if they are cracked when you take them out. If this is the case, you'll also need to have the BB shell re-tapped.

www.aebike.com look in component catalog under bottom bracket and at the YST offering. $10, probably a screw in replacement unless you have Italian or French threads, in which case check out Harris
Cyclery (under Sheldon Brown). Next cheapest is Shimano Sq Taper sealed bearing drop in eg UN54 at
Aebike.com though these seem to all be plastic cups now ($24). The YST will work with your present axle most likely.

The others I recognize but what is JIS bottom bracket threading? Do you mean the spindle taper?

JIS is a Japanese standard threading.

Chombi

I have a Shogun, its made from japan. Do you think mines would be JIS?

I know what JIS stands for. Hoewever, every Japanese bike I've ever seen, including those from the early 80's, has had English bottom bracket threading. The only JIS spec parts I'm aware of are headset cups and crown races and bb spindles.

What exactly is JIS bottom bracket threading?

There are some unique JIS thread sizes, but I don't believe that they have ever been used in bottom brackets.

You are correct GB, for BBs, "JIS" really applies to the square taper measurement on BB spindles and not the threading, I haven't encountered a JIS threaded BB either. 90% of BBs of BB I've encountered out there seems to be English threaded...........but you never know....

Chombi