It is difficult talking about ball bearings since the subject often veers in so many inappropriate directions including side to side play in the wheel of your dirt bike.
But these little buggers tend to wreak havoc on your ride often without you knowing.
Take the wheel bearings, for instance, located in the hub of your wheels. Riding with bad wheel bearings probably produces little more than a grinding sound or perhaps you might feel some chatter. Regardless it's a drag, literally, and you're more likely to uncover issues with the bike on a stand where you'll notice the wheels not moving freely or a bit rough. Also, grab a handful of tire then push and pull the wheel side to side, again while on a stand, (you'll need to hold or have someone hold the handlebars for the front) and bad bearings generally create that unwanted side to side play or what we call slop. The wheels should remain stiff when jerked.
Of all the ball bearings helping your dirt bike roll along, the wheel bearings encompass the ones beaten up the most therefore requiring more frequent replacements. Wheel bearings carry the most load, they move when the bike moves and all the dirt and debris from the ground eventually makes its way inside the hub.
Bearings don't last forever. So take care of them. It's not hard, perhaps a bit tedious, but easy peasy when changing your tires.
Remove the rubber seal to get at the wheel bearings
Wheel Bearing Maintenance
First, remove the seals. Use a flathead screwdriver or similar to work the seals out. Clean the seals and grease the backside which helps repel moisture, prevents drying and lubricates surrounding moving parts, like the axle.
Speaking of the axle, clean it and lightly grease the shaft. Add some anti-seize to the threads. Finally, clean the wheel spacers and check for grooving. If you find grooves replace the wheel spacers since this allows moisture into the wheel hub.
How to Install Wheel Bearings
Replacing the wheel bearings on your dirt bike is a bit more involved than maintenance but you don't have to handle the individual little balls since most manufactures sell them pre-sealed (enclosed, i.e. not the rubber seal) and ready for installation. (If you have non-sealed bearings you'll need to grease them but know they wear out faster than sealed.) In simple terms, you pop the old ones out and place the new ones in but you'll need to remove some things first.
Mechanic's Tip: Place new bearings in the freezer. This causes the metal to contract making installation easier.
If you haven't decided on a wheel bearing set, grab one. SKF makes a high-end product, while Pivot Works is mid-range and All Balls is a best seller because of its price point. Pivot Point and All Balls also make upgrade kits that offer upgrades over OEM and provide longer life.
A bearing puller makes your life a whole lot easier when removing the wheel bearings on your dirt bike
You'll need a basic socket set to remove the axle pinch bolts located at the fork and the axle nuts. Remove the seals using a flathead screwdriver. For all that is good and holy, use a wheel bearing removal tool or blind bearing puller set if you don't want to blow a gasket . Otherwise good luck, grab a six pack and tell the kids to get lost.
Grab a rubber mallet and finally a socket that is equal in diameter to the bearing but smaller than the bearing bore of the hub.
Remove the seals and any snap rings or bearing keepers. Pull the wheel bearings outwards from the hub. Be careful not to drive them in further. Once removed, set the new wheel bearings in place and gently and evenly tap into the hub. Once seated use the socket equal in diameter to continue tapping the bearing until seated.
Mechanic's Tip: On the rear hub, some models require two bearings on the sprocket side.
Turn the hub on the other side, install a clean and lightly greased spacer - if applicable - and repeat the process with the second new bearing. If possible, leave some space (just a hair) between the spacer and bearings. This enables the spacer to float freely and prevents the axle from jamming when reinstalled.
Once finished, put the snap rings or retainers back in place. Now push the greased rubber seals in gently using the mallet or your fingers.
Reinstall the wheels and go ride.