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.
tdb/GFM 1/2007
See also: