Wheel bearing replacement.

First, here is a picture of my KTM front wheel.
#9 and #6 are seals.
#4s are the two bearings.
#3 is the spacer tube (not replaced).

BTW, the KTM part number for the bearings is:
#4 Item #: 0625069047 GR.BALL BEAR.6904 DDU2CG23S6NM Quanity On Diagram: 2 Cost Each: $17.25
The actual bearing number you can use at a bearing shop is 6904. As this bearing is sealed (not shielded) on both sides, it is a 6904-2RS.
Here is why all of this matters: Do an internet search for 6904-2RS and you will find costs well below $10 each.
    10 pack for $19: http://www.ty-coon.com/proddetail.asp?prod=genbearing10pk276
    These are probably Chinese, but  the quality of Chinese stuff is now usually where it should be (except for gluten in cat food!)
Here is a bearing primer: http://www.gizmology.net/bearings.htm
 

Remove the wheel from the bike. Duh. Remove the spacers.

Support the wheel on a couple of 2x4s or, in this case, a BD WorkMate. Don't mess up the disc.

Remove the seals. I use a screw driver. This will ruin the seal unless you are very careful. If you are replacing the bearing you should be replacing the seal as well. Rotate the screw driver (as if tightening / loosening a screw) once you have the tip under the inside lip of the seal. The seal should slid up a bit. Move around the seal and repeat.

One side of this hub has a locking spring clip to keep the bearing from working its way out. A pick and small screw driver are used to remove the clip. Wear safety glasses.

Pry out and up, work slowly around the spring clip.

My front hub (as most MCs) has a spacer tube the keeps the bearings / hub from sliding too and fro. Mine doesn't have any notches in it so I have to knock it slightly to the side so that I can get some purchase on the inside of the bearing with my punch (a rivet tool, actually).

The bottom of the punch/drift is just above the bottom bearing. I will tap on the side (opposite my hand, same side as hammer) to push the tube a bit to the side. Once that is done, put the end of the punch on the inside race of the bearing and bang downward. Move around the bearing as you do this as you need to keep the bearing square with the machined recess into which it fits. The inside tube will loosen and be easy to move to the side.

Once that bearing is out, the tube falls out too.

Turn the wheel over and bang out the other bearing. (You may note that the pictures don't quite match this ... the brake rotor seems to always be down ... Yes, I removed a bearing without taking pictures.) You can see the bearing in the bottom of the hub. You are going to hammer that down and out. Again, work your way around the bearing in order to keep it square with the hub.

Clean the hub with brake cleaner and compressed air. Brake clean evaporates away, leaving nothing behind.

To insert a bearing, I use a socket that is about the same size as the bearing. One of these bearings (rotor side) has to be driven about 1 cm into a recess. For that I use a socket that is just a bit smaller in diameter. For the other bearing, and to get the rotor side started, I use a socket slightly bigger. I place the ratchet end (the one with the 1/2" square drive) against the bearing and hammer on a 2x4 scrap held against the socket.

Don't forget to put in the spacer before you insert the second bearing.

You can see that I am using the larger socket to get the bearing started and then flush with the hub. After that I will use the slightly smaller socket. The drift can be used as well, but be very careful to hit only the outside race of the bearing. Do not hit the inside race.

Snap ring. Wear safety glasses. Check the rotation of the wheel after you get the snap ring installed, as you may have to drive the bearing down a bit more. The bearings should allow the wheel to rotate smoothly, without grabbing / notchiness.

Speedo side has these parts. Don't forget them.

Now to insert the seals. I use both the rivet tool (flat on the end) and a length of 3/4 x 3/4" hardwood scavenged from the shop at work. Do not mess up the sealing lip that contacts the axle / speedo drive. Work your way around the seal, keeping it square. Use the hardwood as you start to make contact with the hub so as to not harm the hub.

Insert the opposite side seal. You are done.