It's not normal for the jam nuts to loosen.

The Ritchey Logic headsets of that era were rubbish. I recall seeing several of them fail on Bridgestone MB-series bikes, through no fault of the owner. In one case (at Allegany State Park on a major downhill section) the rider almost went over the bars. Turned out the lower bearing race had cracked. The bike had to go back to Ray's warranty.

Better choices: (designated for road, but will work for an MB-1)

Tange Levin
Dura Ace 7402 (cartridge)
Shimano 600 tricolor (cartridge)
Campagnolo Record; Chorus
Stronglight A9
Chris King