A few months ago, I took an old mountain bike to my LBS for shifting problems, and they pointed out that the Shimano cranks on it had been recalled 16 years ago. Apparently many of these bikes with recalled cranks have never been brought in for replacement of the faulty parts, which had a high failure rate, not most bikes but often enough that the CPSC and Shimano agreed that Shimano should replace them as warranty items. The pleasant surprise was that Shimano is still honoring the recall, replacing the crankset, bottom bracket, chainrings, and chain, all at no cost for parts and labor by the LBS. (I don't remember if I paid for a new cassette or if Shimano did.) I got a new drive train installed for very little cost.

Here's the recall notice: http://www.cpsc.gov/en/Recalls/1997/...le-Components/. Check your old bikes of the mid-1990's vintage to see if the Shimano part number on the inner surface of the drive-side crank arm has the recalled number.