I used NTN (Japan) electric-motor grade bearings for my wheel rebuild. The OEM bearings were NTN, but I opted for double-sealed ones. So far, they have been great.
Have used 2 sets of these, with no problems..except human interference at times, namely me and a hammer, don't ask.
On both an '79 and a '81 cb650.
Double sealed bearings might have been available in the day when these bikes were new, but considered a little over the top as far as what is needed, or possibly $$ considerations.
Double sealed is IMO the only way to go with wheel bearings.
l8r
