One area that scares alot of atv owners is replacement of these items. It is a simple job that most everyone can do without spending big dollars on equipment. I will state that I prefer to use a shop press, but as long as you take your time and use the correct size tools you will have no problems at all.
Once the hub has been removed from the spindle, you will need to remove the 2 small thrust washers located on each side of the hub. These can be lifted out with your finger.
I have to jump ahead a step here so you understand what you will be doing. You will need a rounded brass punch or in most cases you can use a 11 or 12 mm deep well socket. The rounded edges of the socket will keep from damaging the spacer.
In this picture, you can see what you will be doing when using the punch or socket to drive out the small bearing. This does not require alot of force, merely a few taps with a hammer and the socket will drive out the bearing. A slide hammer can also be employed, but more times then not there is no room to get the jaws inbetween the spacer and bearing.
With the small bearing and spacer now removed, flip the hub over and you will see down into the larger bearing. Again, an appropriate sized brass punch, shop press or the trusty old 13/16th spark plug socket will work. The biggest thing is to make sure whatever you use to drive out these bearings is sized to fit on the outer most metal edge of the bearing. Too small of a tool and you will be driving on the red grease seal. This can damage the bearing (if it is too be reused) and it can also cause you difficulty in getting a decent drive to remove the bearing.
Again, these get gently tapped out, I can hold the hub in one hand and tap the bearing out without beating on anything!
After you have the bearings removed, it is time to either inspect or replace the old bearings. As cheap as they are, once a season is enough for the average rider, more if you race or ride in alot of mud and water.
Re-installation is the reverse order of the take out. Again, for the sake of those that do not have a press Ive used sockets. And I stress again, you should not BEAT on anything...tap tap tap it in.
A small film of grease on the inside of the bearing area will aide in the re-insertion
Once the small bearing (outer) is fully seated, flip the hub over and install the spacer. This is where you can jack the process up, it needs to be installed in the direction it came out. If you are unsure, look at the taper on the spindle and you will see exactly how it should face.
The large (inner) bearing is next, fully seat it against the tapered spacer. You should just be able to get the spacer to move side to side with your finger when the bearing reaches its "stop" in the hub.
Thats it, re-install the seals and small spacers and you have completed this maintence item.