Thanks, guys, this is all very helpful!
I have three or four of those Sanyo Dynopower generators, all with the same problem; the dynamo bearing has gone bad. They scream bloody murder if used. I tried dribbling oil into one, but don't think it worked. Maybe I should just immerse it in oil for a year or two.
Bottle dynos are usually straightforward to disassemble. Not so the BB types?