Temperature change

• If the bearing's outer race is a tight fit in the casing, the aluminium casing can be heated to release Its grip on the bearing. Aluminium will expand at a greater rate than the steel bearing outer race. There are several ways to do this, but avoid any localised extreme heat (such as a blow torch) -aluminium alloy has a low melting point.

• Approved methods of heating a casing are using a domestic oven (heated to 100°C) or immersing the casing in boiling water (see illustration 5.12). Low temperature range localised heat sources such as a paint snipper heat gun or clothes iron can also be used (see illustration 5.13). Alternatively, soak a rag in boiling water, wring it out and wrap It around the bearing housing.

5.12 A casing can be immersed in a sink of boiling water toaid bearing removal

A

Warning: All of these methods require care in use to prevent scalding and burns to the hands. Wear protective gloves when handling hot components.

5.13 Using a localised heat source to aid bearing removal

• If heating the whole casing note that plastic components, such as the neutral switch, may suffer - remove them beforehand.

• After heating, remove the bearing as described above. You may find that the expansion is sufficient for the bearing to fall out of the casing under its own weight or with a light tap on the driver or socket.

• If necessary, the casing can be heated to aid bearing installation, and this is sometimes the recommended procedure if the motorcycle manufacturer has designed the housing and bearing fit with this intention.

REF-16 Tools and Workshop Tips

5.18 Example of ball journal bearing with damaged balls and cages

• Installation of bearings can be eased by
placing them in a freezer the night before
installation. The steel bearing will contract
slightly, allowing easy insertion in its housing.
This is often useful when installing steering
head outer races in the frame.

Bearing types and markings

# Plain shell bearings, ball bearings, needle
roller bearings and tapered roller bearings will
all be found on motorcycles (see illustrations
5.14 and 5.15). The ball and roller types are
usually caged between an inne' and outer
race, but uncaged variations may be found.

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