Vespa smallframe engine strip down and rebuild.
3. Removing the clutch.
The clutch on a smallframe Vespa can actually be replaced with
the engine in situ, as it has its own access cover. You would need
to drain the bike of oil or lay it down on its side (flywheel and
kickstart facing down of course)
To get at the clutch cover you need to remove the
rear wheel and the clutch cable if you have not already done so.
Also remove the rear brake/hub by removing the split pin and undoing
the central castelated nut. On an alloy wheel there is a thick washer
underneath the nut as well which needs to be kept safe. Now you
need to undo the three nuts which hold on the rear hub backing plate.
It is not necessary to remove the rear brakes to do this, but if
you are replacing the brakes (and they are cheap, so you ought to)
remove them now and give the backing plate a damn good cleaning.
The hub backing plate contains the rear hub oil seal,
which should be replaced with a new one. As seen in the picture
below the spring needs to face into the engine. There should be
a gasket between the backing plate and the engine which should be
replaced when you reassemble.
Once the rear hub is removed you will be able to remove
the 6 bolts that hold the clutch cover on.
Note that I finally decided to clean my engine
just before I did this! When you are done this site will greet you.
There is another gasket for the clutch cover which needs to be renewed.
To remove the clutch you need to remove the thrust plate.
This is held on with a springy loop of wire. If you insert
a small flat-bladed screwdriver into the larger of its two
holes then you can shift the wire out of the way and out it
Once this is removed you will see a nut above a tab washer.
Bend the tabs on the washer down with a screwdriver and undo
the clutch wants to turn you may need to jam it. There is
a proper tool for this but
the easiest method is to jam a coin in between the cogs on
the clutch basket and those on the primary drive. American
are perfect as they are a soft metal. Despite never having
been to the USA I appeared to have a stack of them so to
the British economy I used the American coinage. British pennies
are copper over steel and too hard, although older ones will
be pure copper and might do. You will need to repeat this
when you want to remove the primary drive and crank. Here's
what happens to the pennies. The fact they are so distorted
means your gears aren't.
With this nut removed the clutch will be free, but
jammed onto the driveshaft if it was fitted properly. Use the proper
clutch removal tool for this. It screws down onto the inner clutch
basket and has a central bolt that you tighten down and then tap
with a hammer to loosen the clutch and remove it from the outer
clutch basket. The clutch is located on the driveshaft with a woodruff
key (a small half-moon shaped piece of soft metal). Make sure you
remove it when you remove the clutch, and don't lose it! Buy some
spare ones beforehand as it's a stupid tiny thing to be holding
up a rebuild while you wait for new ones in the post. It's not meant
to take any load - the clutch being forced onto the tapered crank
does that, but it is meant to locate it in the correct position.
When the clutch is removed you'll see this:
If you don't have a Vespa clutch spring compressor
you can make a perfectly good alternative with a long bolt, a nut
and 2 big washers - about 60p from my local ironmongers. At least
one of them needs to be bigger than the thrust plate you just removed
but small enough to fit inside the thin aluminum ring (this is very
soft metal and will not take the pressure). Pass the bolt through
the centre of the clutch and put the big washer on it and tighten
it all down to compress the spring, and then you can remove the
circlip with your finders, some pliers, etc.
Inspect all clutch plates and replace the cork-backed
ones if they are worn down. They are so cheap it isn't really worth
not doing it. The new ones must be soaked in gearbox oil for 24
hours (or as much time as possible) or you'll be doing this all
over again really soon!
You should also replace the clutch spring if you are
replacing the plates - they are so cheap it isn't worth not doing
it! If you are not also replacing the metal plates scuff them up
with sandpaper to take off any glaze. When reassembling the clutch
make sure everything is the right way up. in particular the top
plate should be orientated so that the bevel is visible, as in the
picture above. Finally, when reassembling the clutch you must make
sure that the circlip ends are both located in one of the inner
basket grooves and not in the gap or your clutch can and will come
apart when you least expect it.