Note. The double row roller bearing is filled with grease and hermetically sealed and does not require maintenance. Do not remove the bearing unless absolutely necessary as this will damage it. Do not overtighten the drive shaft nut in an attempt to "adjust" bearing.
Note. A press is required to sort the assembly; if not available, use a large bench vise and suitable shims (big nest type). The inner rings of the bearing are pressed onto the hub; if they remain on the hub after removing the latter from the steering knuckle, a suitable bearing puller will be required.
Examination
1. To check the front wheel bearing for wear, measure the side play of the hub. Install the micrometer so that its probe rests against the outer side of the hub flange. The play should not exceed 0.05 mm. If not, the bearings are worn excessively and should be replaced.
Replacement
1. Remove the steering knuckle assembly as described in Section Removal and installation of assembly of a forward rotary fist, then unscrew the screws securing the brake disc guard and remove the guard from the hub.
2. Tighten the steering knuckle securely in a vise. Using a suitable spacer, push the hub out of the bearing. If the bearing inner race remains on the hub, remove it with a suitable bearing puller.
3. Remove the bearing circlip from the inside of the steering knuckle assembly.
4. Where necessary, place the inner race in position and support the inner surface of the steering knuckle. Using a suitable spacer (it must rest only on the inner ring of the bearing), push the bearing assembly out of the steering knuckle.
5. Thoroughly clean the hub and steering knuckle, removing all traces of dirt and grease. File away any nicks or burrs that might interfere with assembly. Check components for cracks, other damage, and signs of wear, and replace if necessary. As noted above, the bearing and circlip must be replaced each time they are removed. Purchase a bearing replacement repair kit that consists of the bearing, retaining ring, and driveshaft nut and washer.
6. When assembling, make sure (if it is possible), that the new bearing is filled with grease. Apply a thin coat of oil to the bearing outer race and hub contact surface.
7. Before installing a new bearing, remove the plastic covers protecting the seals, but leave the inner plastic sleeve in place to hold the inner races together.
8. Reliably support a rotary fist and place on it the bearing. Move the bearing to its working position, making sure that it is not skewed. Use a suitable spacer that only rests on the outer ring.
9. Once the bearing is in place, secure it with a new circlip and remove the plastic bushing. Apply a small amount of grease to the sealing lips of the stuffing box.
10. Turn the hub upside down and place it securely on the props. Place the steering knuckle on the hub and slide it into position using a spacer that rests on the bearing inner race (refer to accompanying illustration). Make sure the hub rotates freely and wipe off excess oil.
11. Establish a protective casing of a brake disk on a rotary fist and tighten screws of fastening.
12. Install the steering knuckle assembly (Chapter Removal and installation of assembly of a forward rotary fist).