[J57ltr]

I have seen tons of bearings that are bad but look great on the outside. When you get small particals of dirt and grime stuck between the race and balls of the bearing it can cause the ball to stop spinning and to spall the inner surface of the race and damage it. Usually it will feel gritty and may hang up when you spin it. Its like you are pushing a shopping cart and run into a pebble and the wheel stops but you end up pushing it another foot or so (or like riding a skateboard and hitting a pebble). You can't see it from the outside, but you can feel it.

Shields do not contact the inner race so there should be no resistance for a bearing that small when turned by hand. If there is grease in it may not spin freely, but you should not feel any grit or clicking, it should be smooth as silk. If it is gritty change it since you have it apart if you don't then you may get to a point where the bearing inner race stops all together and the shaft turns and the inner race does not which will destroy the shaft.

As far as getting the old one out if you do not have a hydraulic press use a heat gun as mentioned earlier and a drill press if it is glued then you will need the heat gun so you don’t damage the bearing housing (from pressing too hard). Use a socket that is the same size of the inner race to press the old one out since you are not worried about damage to the bearing at this point. When you press the new one back in you can use sleeve retaining compound to hold the bearing in and its available at most auto supply stores (Advance, Hi-Lo, Checkers (or its affiliates) carry it. When pressing the new bearing in make sure to use a socket that is the same size as the outer race of the bearing and press on the outer race only. If you press the inner race to put the bearing in you can damage it because the inner race will press on the balls which will press on the outer race, this will cause indentions in the race and you will have a bearing that clicks and be back to square 1. You can also damage the balls as well pressing on the inner race.

A 625ZZ bearing comes back as a 5mm ID, 16mm OD, 5mm Wide bearing the ZZ is for shielded both sides.

If you live in or near a large city or in an industrial area you can buy bearings from places like Motion Industries or Applied Industrial Technologies, King Bearing or Purvis Bearing. An ABEC 1 bearing should be fine since most of the motors I have seen use these although I would feel better with a more precision bearing like an ABEC 5 along with a seal instead of a shield.

Jeff