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Rebuild Tutorial:
Special Instructions for bearing & seal
replacement
- Introduction
- Bearing and Seal Replacement
- Disassemble
- Assemble
See
Photos
Cleanliness is a keyword when performing
this operation. Start by cleaning
crank case assembly. When the case
is split cleaning of all old sealer
needs to be done before installing
new parts. The workplace should be
an area that supports not only cleanliness
but is not abusive to the aluminum
crankcase castings. Wood is an excellent
choice. Temporary covers (cardboard)
for steel top benches can be used
that will also offer protection.
After disassembling the crankcase the replacement
of the seals and bearings can be accomplished.
The removal of the seals can be done with a
soft (plastic/wood) round driver that fits
the seal radius so that a light tapping with
a hammer will remove the seal.
Heat is used to remove the bearings without damaging the crankcase bearing pockets. There are generally two methods that are used. (1) With oven large enough for the case(s), heating to a temperature to maximum of 150 degrees or by using propane torch to heat the material locally around the bearing(s). During the heating process the new bearings are placed in a freezer for cooling.
When the case(s) is at temperature remove and place on workbench face down. Tap bearing out with a soft round driver. Drop in cooled bearing tapping gently (on high side) if bearing becomes cocked. Bearing will bottom when square with pocket.
To install new seals: start seal in pocket then tap gently using a flat smooth soft block that will bottom on crankcase when seal is home.
Cases are now ready for re-assembly:
1. Apply a good sealer (Yamabond) to both
case half mating surfaces. Apply evenly to
entire machined surface.
2. Install 5mm clutch actuating rod
3. Insert crank assembly into one case half
4. Gently work other case half over crank
nose and transmission shafts
5. Tap (wood block) and work until the two
halves are mated
6. Install all fasteners evenly until cases
are squarely mated. Torque values for the 6mm
screw are available but common sense works
just as good. Remember that the steel screws
can damage the aluminum cases if over tightened.