Vespa smallframe engine strip down and rebuild.
5. Splitting the cases.
Having removed the flywheel and stator plate you are now ready
to split the cases. Essentially this involves nothing more than
undoing all the case bolts and studs and pulling the case halves
apart. Indeed the Vespa service manual suggests that's all there
is to it. Not quite. The cases will be an absolute bitch to get
apart, and you need to apply both brute force and gentle persuasion
in equal measure, all the time being careful not to risk causing
any damage. The picture below shows most of the bolts and nuts
you need to undo. There are a few more round the other side you
can't see in this picture.
Two of these nuts are attached to studs which remain in the case
half rather than bolts which are separated. In the picture above
these are marked in red. All the rest are bolts. To make it easier
to reassemble the engine make sure you pair each nut/washer/bolt
after removal and preferably label them so you know which bit of
the engine they are from. They are all different sizes, so it's
not essential, but why make things harder?
Once you have all the nuts and bolts out you will find it quite
difficult to separate the cases. Essentially, various bits of engine
are holding the cases tohether. You need
to basically go methodically round
the cases further apart, levering here, wiggling there, a light
tap here, a sharp yank there until the cases are separated. This
is probably the hardest part of the whole rebuild, so once it's
done have a beer.
Always keep in mind that these cast aluminium cases are very fragile
and brittle in places. Do not apply direct blows to the aluminium,
but use something fairly blunt and soft as a drift, and when levering
the cases apart use something softer than the alumunium, such as
wedge. You can also use the kick starter as a good levering point,
and turning it will help. Do not apply anything but the lightest
pressure to the cylinder opening, as a dent or hole here is absolutely
the last thing you want. Just be patient and keep pushing, pulling,
wiggling and levering until the cases pop apart. Once they have
done so you'll be faced with this (the crank has already been removed
in this picture - would normally remain in the left hand case half.)
Left hand case half (crank removed)
Right hand case half. You can see how the kick
starter, driveshaft and gears would hold the cases together.