I have a 1984 ST-500 and the BB is the cartridge style. There is a lot of adjustment so the crank set can be adjusted in or out from the frame. I forgot to measure mine when I took it apart so I set it up and moved the front derailer in and out and it was OK. My BB was dry as a bone and since it is a sealed unit I drilled a 3/8" hole in it and filled it with grease ,covered the hole and remounted it. It is now quite and runs smooth. I will change it if I ever start using the bike.
OK guys where do I get a replacement BB like this one.
Ed
Ed