Note: You should probably grease or lube your bearings (after cleaning them) if you are using them for their intended purpose. I was going to use these bearings for something that didn’t require fast rotational speed, so that’s why I didn’t lube them.
Instructional video on how to disassemble, clean, and reassemble a ball bearing. Here it’s a standard skateboard wheel ball bearing. The procedure should be similar for most other types of ball bearings, including for bikes, motorcycles, rc cars, etc.