Bottom bracket problem
 

It rained in my commute last Thursday. I cleaned (hosed off and dried) the bike and lubed the drivetrain. The following Friday, and Saturday, the bike did not show any signs of trouble. I rode over 80 miles between those two days. Sunday, I was going to get the bike ready for Monday's commute when I noticed, the crank would only pedal backwards. I took the chain off the chainrings to isolate the problem and see if it is the bottom bracket. Sure enough it is. This is an old steel bike (circa 1989), with Suntour Sprint cranks and bottom bracket. Have any of you had this type of problem? Please describe the damage inside the BB, if you have had the chance to work on it. Thanks.

Well, I don't have x-ray vision,so why don't you just pull it apart and see? It may be rebuldable,or completely trashed.

When was the BB was repacked with grease? Please don't say 1989.

You're going to have to disassemble the BB to see what's wrong. Remove the cranks, loosen the adjustable cup lockring, remove the adjustable cup, and carefully remove the bearings and spindles. If nothing is damaged, then new bearings and a slathering of grease should do it.

OK, got my bottom bracket, NOS - Shimano UN73, a sealed one. The one I am replacing is not the sealed kind. The old BB can be overhauled but I decided to go sealed. My question is which side goes on the left, based on the attached image. Thanks in advance for the reply/ies.

Excellent! Thank you.

Did you get a spindle length to match the old one?

I think they match (or close enough) since the new BB is installed and the smaller chainring lines up with the middle cog (7-speed, Regina). Shifts just fine.