Been cleaning your bearing all day with different kinds of solvent and still got dirty bearing? try the paper slip method.

What you need:

1. Dirty bearing.
2. Small pieces of paper cut as shown below, must be clean.
3. Solvent/mineral spirit.

How you do it:

1. Cut small section of paper in sharp triangular shapes, and fold it in half to increase its strength.
2. Slip the paper between two balls until it stops going any further.
3. Pinch both ends of the paper, close to the outer race.
4. Spin the outer race of the bearing, letting the paper rub the inside part of the outer race.
5. Take the dirty paper out, swap with new paper, do this until it’s clean.
6. Do this also with the inner race if necessary, most likely you don’t need to.
7. Clean the bearing with solvent/mineral spirit.

really cool. Never even thought of that.

I didn’t invent this, I read about this method in yoyonation quite some time ago and surprisingly it works very well.

See also: Elephark’s original thread on paper cleaning, which is stickied within the Useful modification and maintenance guides thread.

I have also added your thread to the sticky because your pictures do a good job illustrating how to do it.