If there is no plastic involved, get a couple cans of aerosol brake
cleaner from an auto supply to clean out the grease. Bear in mind that
you can wash all the grease out and still leave the grit trapped in the
bearings.
If at all possible, replace the bearings. They are almost certainly
stock bearings and readily available.

ss wrote:
I have a tricky issue involving repacking a pair of bearings. My
unique bicycle (GT I-drive for those keeping score) has a non-standard
part called an eccentric, which is an aluminum tube about 9.2 cm in
diameter and 6.8 in length, in which 2 bearings have been pressed.
They are large circular, with the ball bearings between 2 "U"s and a
very thin metal sealing strip on each side. Well, long story short,
when the bike was manufactured, all sorts of aluminum machining debris
wound up in the eccentric, and even some specks in the bearing
assembly. Needless to say it is a little scratchy running. I have
cleaned it once with good results, but I can still hear a couple of
bits of debris on each one. I am going to go for broke and clean and
repack it again to get it running as smooth as possible.

Due to the nature of the beast, it cannot (by me) be removed (I don't
think - anyway I really don't want to damage the unit). The bearings
appear to be pressed in, stopping against a metal bearing retaining
ring (a kind of 15/16ths metal circle that clicks into a small
groove).

So, in order to do this, I will remove the outer seal strips and take
them away. The inner strips and o-ring locks will remain "trapped"
between the 2 sets of bearings for this operation (while the unit is
dry, I plan to tape them in place in the very middle to keep them out
of the way). The question:

What is the best cleaning method to make sure I get all debris out?

I think I can mount the bike in a stand with the part in question over
the sink, and so I am thinking of scrubbing with degreaser and a
toothbrush in between blasts of warm soapy water (from the faucet).
Then air dry (blowdryer) and repack. Obviously I am not a machinist,
and really if you haven't figured it out yet don't know what I am
doing, so hopefully some of the experts here can give me some help.
Thanks in advance.