Replacing the wheel bearings
How to tell when your bearings need replacement
Wheel bearings are generally treated in an “out of sight, out of mind” manner, but these few little pieces of metal are what keep your wheels going round and round.
Actually, your bike will do an unintended stoppie long before they get to this point. However, if they resemble the ones below in any way, including the missing balls or the rust, they should be replaced immediately. This is a safety issue, and a cheap one to take care of.
If a bearing is bad enough that it needs to be replaced, you will usually be able to hear it making more noise than usual when you're riding. You should also be in the habit of checking the bearings every time you have the wheel off, and regreasing them as necessary.
When inspecting, keep these things in mind. If they're notchy (don't turn smoothly) when you turn the wheel by hand, they need to be replaced. Also, if there's any lateral play (the wheel moves side-to-side) they need to be replaced. They should be a little stiff to turn by hand, but not very stiff if you're rolling the wheel while it's still on the bike. Bearings are dirt cheap to replace and should be done if there is any question.
How to find replacement bearings
What you'll find when you pull the wheel off and look are two bearings and a tube of some soft metal that runs between the inner races. When you snug the axle down, it pulls everything tight on the center race of the wheel bearing, and that should be the ONLY place it's tight. But stock bearings are only sealed on one side and usually won't last the life of the bike. You want to replace them with double sealed bearings. These will have the same part number, but will have an SS or ZZ at the end of the number.
The easiest way to find the part number you need before you start disassembling everything is to go to the Ron Ayers parts fiche and look up the part numbers for your year of bike. Yes, every year should be the same, but you need to be sure. You don't, however, have to (or want to) order them there, or even at a bike shop. Search out the bearing supply place closest to you. If you can't find one, a good auto parts shop should have what you need.
Bearing part numbers are fairly universal (ie... a #6203 bearing from any brand will be the same, fit-wise). There are two wheel bearings for the front (usually the same). There are three in the rear: one on each side and one in the sprocket carrier. These are usually three different part numbers. Make sure you keep track of which bearing goes where. You don't want to be trying to pound your new bearing into the wrong place.
Here's what you should find when looking up the part numbers for your wheel bearings, along with the standard sizes for that bearing number:
Again: You don't want OEM bearings. They're single seal bearings. You should find instead a fully sealed (double seal) variant. Also, don't be surprised if the bearing that fits isn't listed as a wheel bearing; the front wheel bearing that fits the 250 and the Concours (same bearing) is usually listed as an alternator bearing. The double sealed bearings are maintenance free; if they get "notchy", toss 'em and replace 'em.
If you're having trouble finding your bearings, try looking at places that sell/work on ATVs or snowmobiles. They use many of the same bearings we do.
If you already have the bearings out of the wheel, the process is even simpler. Look at the side of the bearing's outer race (the part that touches the wheel). There should be a number there. That will be either a bearing industry number (or a variation thereof that you can decode), or a size (which would look something like 25x12). With that, you can walk into the store and match it up. It'll be even easier if you can carry the old bearing in. Get bearings from a respected manufacturer of bearings. There's no use tearing all this stuff apart just to put a Chinese bearing in there.
For more information on bearings, see this FAQ article.
Removal of old bearings
Wheel bearings are simple. You'll want two small sections of 2x4, or a milk crate (same stuff you'd use for changing tires) to hold the rotor off the ground. For removal, the Motion Pro 8 Piece Metric Bearing Remover Set, or something similar, is the correct tool for the job. The short piece fits in the axle opening. The long piece has a wedge that fits in the slot of the short piece, which allows the whole thing to 'grab' the inner race. Then, as you beat on it with a hammer, it should work the whole bearing out evenly (it doesn't always, but it works better than anything else.) As usual with Motion Pro, Googling should yield a better price than the MP site.
Another alternative is a bearing puller. This particular puller needs a flat, sturdy surface to push against, with two points on the opposite sides of the bearing, 180 degrees apart. As you will notice, there really aren't any on the wheels. So, lay two bars of scrap metal across the wheel, close to the bearing, to provide support.
If you don't want to spend the money on the tool set, you can sometimes get by with a drift (aka a punch), or a long 3/8 drive extension. Some have had success with a BFSD (large screwdriver). Some have had no success and ended up getting the Motion Pro tool. Since you're not trying to save the old ones, feel free to bash away at the inner race. The tube that runs through the wheel doesn't usually completely cover the inner race, so you can kind of get a purchase on it, beating the bearing out from the opposite side of the wheel. The down side is that you have to move around the race to get the bearing out evenly, and you're going to have to be careful, because the drift will probably slip off and bust your knuckles a few times (think "leather gloves").
Tools to ease this chore
One tool that makes installation/removal easier is a forced air shop heater. Hold the wheel hub in front of it until it's around 200 deg F. The expansion from the heat makes it marginally easier to remove the old bearings. This also works for installation. Leave the new bearings in your freezer until you're ready for installation, and install them into the heated hub. It reduces the amount of interference just enough to make it easy to tap in the new bearings.
You can use a heat gun on the hub to expand it. Otherwise, a bit of metal may be removed every time you remove or replace a bearing. Some wheels even get ruined this way.
The heat gun works like this: The wheel (and the hub, where the bearing goes) is made of aluminum, while the bearing is made of steel. Aluminum expands faster than steel, so even if both are heated to the same temperature, the interference fit relaxes and the bearing becomes easy to remove. Again, leave the new bearings in your freezer until you're ready for installation, and install them into the heated hub.
Installation of new bearings
For putting the new bearings in, all you need to do is hammer them in. Important: You only want to put pressure on the outer race (the outside rim of the bearing). You can do this with a bearing seating kit (check auto parts stores), or a socket that you carefully hold in place so you don't hit the bearings. You can also disassemble an old bearing and use only the outer race, with a piece of wood on top of it, to drive the new bearing in.
Did you happen to notice the part where we said to leave the bearings in the freezer until just before you install them?
The new bearings should last significantly longer than your stock ones.