This can be quite involved this one, so
you have been warned! Special tools required are the flywheel
holder, and the flywheel puller. You will also need an
impact driver and to have a source of heat, probably a
blow torch is best, other methods will be described later
on. The usual hammers, screwdrivers, sockets, etc are
also on the tools list.
First we need to take the floorboards, off on both sides,
8mm nuts secure these, on the outer runner strip, and
in the central bridge piece. On the kick-start side, also
remove the leg that supports the rear of the floorboard,
these should be 11mm. Exhaust, held by two 13mm nuts,
and one 10mm nut down by the tailpipe is next, there may
also be, depending on your machine, another 11mm nut tucked
away underneath to the rear of the box section of the
exhaust. Last there should be a clamp, where the silencer
meets the U bend. You may also have to tap, using a length
of wood, the box away from the U bend, as it tends to
rust and coke itself on.
Undo the engine oil plug, and drain oil. Carb, undo the
8mm clamp bolt, and again from the rear with a piece of
wood, tap the carb off. No need to undo all the cables,
just be careful to tuck the carb away so it will not get
damaged. Undo and remove all the remaining 10mm nuts holding
the chain case side on, remove the chain case, again it
may need a whack with a rubber hammer, unhook the clutch
cable from the arm.
Moving round to the other side now, remove all the 8mm
bolts round the flywheel housing cowl, and the two on
the side for the cylinder head cowl. Loosen the 13mm bolt
at the top of the cowl, but not tight on the U bend. This
now allows you access to the two 11mm nuts that hold the
down pipe on. The one on the flywheel side is a touch
awkward! With the U bend off, look between the rear wheel
and the flywheel, there is a rubber bump stop on top of
the casing, remove this by prizing a screwdriver in the
bottom off it. Now you can take the rear shock absorber
off to let the engine drop down. The cylinder cowl you
have just undone will now slide off when you take the
spark plug out. Undo the four cylinder head bolts, in
a diagonal method, slide the head off, the head gasket,
and the barrel. You may find the inlet manifold will catch
on the bodywork, but a small amount of twisting and force
will allow you to take it off. If you do not want to do
this, just unbolt the manifold and take it off.
With the piston still in position, trap a piece off wood
between this and the crank case mouth. Be careful that
the piston will not slip off and break. With the piston
moving down against the wood, time to take the front sprocket
off. Loosen the two 10mm bolts that hold the chain tensioner
on, scalene the chain. A 14mm bolt is used to hold the
front sprocket arrangement on, go careful when first undoing
this that the piston is in position on the wood and is
not going to move. Slide all the items of the front sprocket
set up off and out the way, including a small oil thrower
cup washer at the bottom of this set up!
Back round to the piston, remove the two circlips that
retain the gudgeon pin, I use a socket extension bar of
the same size to tap this out! Piston, small end etc,
take them off and put them to one side. Round to the other
side, time to take the flywheel and parts off. first the
flywheel holder, put this in position and undo the nut
in the centre (17mm) which is left hand thread, it will
undo turning clockwise. With the nut removed, insert the
flywheel re-mover and extract the flywheel.
Before you start to remove the stator plate, make a mark
that will allow you to re align the stator when re-fitting,
mark both the stator and housing by scribing a mark with
a screw driver or sharp object. Unplug the wires from
the stator plate in the junction or rectifier box, un
thread them so they are free. Three nuts hold the stator
on, and a further three bolts to undo will allow you to
start taking the stator housing off. You can use the special
tools to remove the housing, but you can easily use two
10mm bolts of around 6mm plus in length to remove it.
You will find two extra holes that had nothing in them,
one at twelve-o clock and one at six. Using equal turns,
otherwise you can easily strip the threads, tighten the
bolts into the housing again take it easy the threads
are delicate. If the threads have gone in here, the only
way to remove the housing is by a long metal rod and hammer
and banging the housing off from the rear, again equal
amounts around the housing and hit it as near to the centre
as you can. Hopefully the bolt method will work and the
housing now starts to come off. It will be fairly tight
as you are breaking the two seals that run on the crank.
It is now easier than it was when the housing was in position,
to remove the two screws that secure the two wiring plates
in position. There is a rubber seal in between these two
plates also, slide them all off along the wiring, you
can now remove the stator from the housing. If you are
going to re-new the condenser and contact breaker points,
Click here for instructions
if needed.
Once the housing is off, turn the crank to BDC (the conrod
at its lowest point) tap the crank from the front sprocket
side, out of the housing, you will need to turn the crank
at an angle to remove it completely. Four screws hold
a plate on where the crank has just been taken out, up
against the drive side bearing. The impact driver is needed
to remove these, as they are dot punched at the factory.
If you do not have access to an impact driver, you may
just about get away with a correct fitting screwdriver,
while twisting the screw undo, tap the end of the screwdriver
with a hammer. Best to get an impact driver though!
Remove the oil thrower gasket up against the bearing,
push the seal out of the plate you have just taken off,
notice it will only come out one way because of a lip
on the plate. If you are not renewing the drive side bearing
leave it in place. If you are, you will need to find a
socket that fits through the hole left when you took the
front sprocket, heat this housing up using a blow torch
and knock the bearing out, using the socket and hammer.
re-fitting the new bearing is in reverse of this, just
make sure you use something that is large enough to place
the pressure of hitting on the outside track. Smearing
the bearing with grease on the outer track will help,
just make sure the bearing goes in square, other wise
you will damage the track.
Last thing to take apart is the mag or stator plate housing,
two seals, some spacers and a bearing all need to come
out. This can be a little tricky so if you are not sure
at all, you might want to pop it along to a dealer to
get the seals renewed! Some people just renew the one
oil seal, is can be false economy but then again it is
hard to re new both oil seals, damage to the mag side
bearing is possible and easy to do. You have been warned!
Just for the brave, the method of removal is this: -
Read ALL of the next section first, and then do the
job!
Remove the large circlip that sits on top of the oil seal.
Flick the oil seal out with a screwdriver. (If you are
just replacing this one seal, refit new seal and old circlip
in the reverse way to removal). There will be on Li, SX,
and TV machines a small spacer ring (used with bearing
NU205), take this out also. Now secure the housing in
a suitable way, what we need to do is heat the housing
up, but still allow us access to be able to tap the bearing
out.
Remember it will be harder to heat the housing and then
place it somewhere safe, as it will be hot to hold! The
best heat source to use it is a blowtorch (butane burner,
or calor gas burner), heat the housing up, and just make
sure you don't melt it. Gas ring on your oven (when the
wife is not looking) camping gas stove, can also be used,
but just remember there will be deposits of unburned oil
on the inside of the housing that can burn off, causing
small holes in your carpet. Use a tray or similar to put
the housing on!
Now what we are doing by heating the housing up is expanding
it, so the bearing will not be so tight to remove. For
removal, you will need to find a socket that fits the
hole (the one that faces out when fitted, the smallest
one) as tight as possible but still fits through. This
is because if you use a smaller one it will not fit on
the outer track of the bearing, so when you start hammering
it out, you will defiantly need a new bearing. With enough
(but not too much) heat in the housing you should be able
to gently tap the bearing out, the remaining oil seal
and cup washer will all fall out also, so take care as
they too will be hot!
If you are re-placing you're mag side bearing a word of
note. You will need to either have the special removal
tool or take it to your local Lambretta Dealer who will
be able to remove for a small fee. On no account should
you try and remove it with heat and tapping it etc damage
will occur to the crank!
That's it, time for checking everything in site and lots
of cleaning! Clean all old gaskets from all surfaces,
I also scrape all old oil deposits form all surfaces.
One note on the crank, it is acceptable for side play,
but you should not have any up and down movement in the
conrod.
Piston, if it has scores or burn marks, a fine grade of
wet and dry sanding paper can be used to get the worst
off. Clean the piston rings and make sure the grooves
they sit in are clean.
It is a good idea to flat the cylinder head while off
as well, to do this you will need a completely flat surface
i.e. a piece of glass or a mirror, sticky backed sanding
disc stuck onto the mirror or glass. Place the head on
the sanding disc and use rotary movement, sand the head.
Turn the head 90 degrees, and repeat, keep going until
you have completed the full circle.
With everything clean, your new oil seals and gaskets,
bearings if needed, you are ready to re-assemble.
Place the mag or stator housing so that the inner part
faces upwards. Now you need to re heat the housing, not
as much as when removing but still needs heat! Keep the
heat at the top of the housing. When heated, fit new seal
carefully as the housing is hot! with spring facing towards
you (it will end up facing into the crank when you have
finished) Fit the L shaped cup washer, if your old on
is not damaged it will be fine to use this, otherwise
fit new. Using again a socket or similar, again making
sure that what you use, puts the pressure on the outer
track, knock the bearing in position. Make sure it goes
in square, tap it fully home. Again Li SX and TV models,
if you are using the original size of bearing (NU205)
fit the spacer washer. GP models and machines using the
larger bearing (NU2205) do not use this spacer.
An alternative method is to stick the bearing in the freezer
along with the pea's for ten to fifteen minutes, this
shrinks the bearing to fit the mag housing.
Fit the larger seal in the housing again making sure the
springs of the seal end up facing the crank when re-fitting.
Re fit the circlip, put this assembly to one side.
 |
Here we are starting with the drive side bearing
set up, shown are the parts needed to fit the bearing.
Good quality grease, bearing, gasket, oil seal and
plate, plus four retaining bolts. |

|
There are three methods to fit the drive side
bearing, heat the casing by means of blow torch
or similar, freeze the bearing as it makes it shrink,
or buy a bearing press tool. There are manufacturers
of tools specifically for Lambretta, if your going
to make a habit of doing these jobs they are well
worth the expense. Using one of these methods, press
the bearing into the engine casing, it does not
matter which way round it goes, but it is important
that it is pressed all the way home. You can check
this by looking at it through the chain side of
the casing, it should fit right up tight against
its housing. |

|
Once the bearing is pressed home, smear the balls
of the bearings with high melting point grease,
|

|
The round gasket is then fitted, some gaskets
will not fit this housing perfectly, do not worry,
just simply and carefully push the gasket edges
into the housing with a flat screwdriver, just be
careful when doing this. |

|
Next we need to fit the oil seal to the plate,
the picture here shows the correct way round it
goes. The spring around the oil seal should face
the the crank when it is finally assembled. Four
new screws are used, it's always best to use new
ones here as the old ones almost certainly will
be damaged when removing them. New ones from most
dealers will now be supplied as high tensile Allen
key headed bolts, it is much easier to secure and
do this type of screw. Lock-tite is always sensible
on these bolts, |

|
The plate is diagonally torque'd, this makes sure
the plate sits down evenly, keep going around them
until you are sure all four bolts are secured as
tight as they can be, there is no torque setting
for these bolts, but you should tighten them fully
until they will turn no further. |

|
With this picture you can see that the oil plate
is fitted correctly, it is vital that the plate
is secured fully home and is flush as in the picture.
If the plate sits proud and is not secured correctly,
your crank will rub against it and not turn correctly,
damage will occur. |

|
Place the mag or stator housing so that the inner
part faces upwards. Now as with the drive side bearing
you need to either heat the housing, keep the heat
at the top of the housing. When heated, fit new
seal carefully as the housing is hot! with spring
facing towards you (it will end up facing into the
crank when you have finished) Fit the L shaped cup
washer next. |

|
Now we need to fit the bearing, it comes in two
halves, put the inner to one side as this must be
fitted to the crankshaft. Either with your bearing
tool or by using a socket or similar, make sure
that what you use puts the pressure on the outer
track, knock the bearing in position. Make sure
it goes in square, tap it fully home. Li SX and
TV models, if you are using the original size of
bearing (NU205) fit the spacer washer. GP models
and machines using a GP crank with the larger bearing
(NU2205) do not have or use this spacer. |

|
With the bearing in position, fit the last larger
oil seal, again with the spring side facing you,
towards the crank when assembled. A large circlips
holds everything in place. With every thing finished
your mag housing should look like this! |

|
Preparing the new crank, if you are not re-fitting your
old crank you will need to fit the new mag side bearing inner
track. The easiest way to do this
is using a proper bearing drift tool, or a deep socket. To ease the fitting of the inner track, you can always place your cranksafht in the freezer for a few hours, this helps to shrink it a touch. Support the crank, if using a vice, use the jaws on the taper side of the cranks web cheek only, this helps to avoid twisting or knocking your crank out of true. Tap home around the whole inner
track to make sure it is seated properly. |

|
Fitting the crank is done by passing the shorter
shaft through first, it is easier to get the crank
at BDC, so the crank is at it's shortest. First
smear a little grease on the drive side inner seal
that we fitted earlier, a very slight coating is
all that is needed. This helps the crank pass through
it, less chance to nip the edge of the seal. |

|
The crank should be pushed as far as possible
by hand, rotating the crank slightly as you go,
again to make sure you do not snag the edges of
the oil seal. |

|
Here we are using a special tool to pull the crank
through, from the chain side position the space
central on the bearing. |

|
The front sprocket bolt is used to pull the crank
through into position. If you do not have this special
tool, fit the flywheel nut on the end of the crank,
this stops you from damaging the thread on the crank,
and using a rubber or nylon hammer, tap home the
crank, again twisting as you go. |

|
Here we can see again, the use of the tool to
pull the crank through, we are also using a con
rod holding tool to position the crank |

|
Note how the crank is fully home now, flush to
the drive side plate, but still turning freely.
|

|
Before you fit the mag housing that we have built,
the first step is the gasket for the mag flange,
this will only fit one way, make sure all the holes
line up with the gasket |

|
Fit the mag housing assembly, this should be a
pretty good fit, wiggle it into position, if its
a little tight, a rubber hammer hit evenly around
the edges will tap it home. If you are using your
original one, it will need cleaning to make it fit
easier. Once the mag housing is just about home,
three nuts on the studs secure this. Again in a
diagonal pattern tighten this fully home. Finally
check the crank still turns freely. |

|
Now you have the mag fitted, we can turn our attentions
to stator plate. |
Re position the stator roughly in the mag housing, fit
new screws, gasket to the securing plates, that hold the
wiring, again this just helps because there is not much
space to do this when the mag housing is in position.
Fit new mag housing gasket, it will only align one way
with all the holes. There is a tab sticking out on the
gasket, this lines up with a notch at the nine-o clock
position on the crank case side. Make sure you align the
three studs fitted, with the corresponding holes, push
on, it will not go far. Use a rubber hammer to knock the
mag housing home, refit three securing bolts, remember
the top one has an arm to trap the wiring down. Align
the stator plate up with the marks you made earlier, fit
the three nuts to secure.
Round to the front sprocket side, fit the cupped oil thrower
washer, cup but sits inwards, front sprocket assembly
is located on to splines, line them up and push home,
with the chain located on the teeth. Now take the outer
washer (the bolt sits in it) push it down the spline.
If you look on the front sprocket shaft you will see a
small oil way hole. Using a felt marker pen, make a mark
on this outer washer that lines up with the hole, this
just eases re-fitting. Take it back off and refit other
half to front sprocket, the two half moon parts locate
together at their lowest point. Spring on next, then the
outer cup you just marked with the bolt through it. Start
to tighten the bolt, while looking at the mark you made
and the hole, it is easier to locate properly. To finally
tighten the bolt you will need to lock the chain to stop
it rotating, I simply wedge the largest screwdriver I
have in between the teeth of the cog and the chain. Tighten
the front sprocket as tight as you can, the outer ring
should at least partially cover the oil way hole on the
shaft. A final check is to smack the assembly with a hammer,
if it sounds hollow re tighten it, as it should sound
solid!
Fit new chain case side gasket and the chain case side,
re-fill with fresh oil making sure drain plug is back!
Check that you have refitted the clutch cable into its
arm, if not, use a pair of grips to move the arm forward
and slip the cable in.
Refit the piston and barrel assembly using new gaskets,
to base, head, inlet and exhaust. Some people find it
easier to fit the piston and rings into the barrel first,
then when the barrel is slid down on the studs, line the
conrod up with the piston, (having first inserted the
small end bearing in the conrod, slightly oiled) piston
that just pokes out the bottom enough to be able to tap
the gudgeon pin in and re fit the circlips. When tightening
the head down, this should also be done in a diagonal
method, to 20 N.M., (the book states 15 but 20 is better).
Re-fit flywheel and then check that timing is all correct
and present still.
Click here
for instructions on this.
Finally re-fit both cowlings, cylinder head and flywheel,
re-fit, carb, exhaust, plug the wires from the flywheel
back in to the junction box or rectifier.
Turn on and start up!