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Removing a Lambretta Engine

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					    Removing a Lambretta Engine
    The Lambretta engine is very accessible but there are some projects that are much easier if the engine is removed from
    the frame. This series of images is from a Series III Lambretta but should be very similar for all Series I - III bikes.
    You'll need:
             A 24mm socket & driver or a large adjustable wrench
             A 3.5mm allen head key
             A flathead screwdriver
             Small adjustable wrench
             A hammer and punch or block of wood
    Start by putting the bike on the stand. If the bike is in running condition, turn off the gasoline, start the engine and run it
    until the carb runs dry. You can also drain the oil but it is not a required step (but you'll have to do it later if you are
    planning a rebuild).




    Remove both side panels from the bike and have a look at what is connected from the frame to the engine. On the left
    side of the bike, the fuel line, throttle cable, choke cable, and air filter intake rubber all need to be disconnected from the
    motor.




    To remove the air filter neck, loosen the retaining collar at the carb mouth with a flathead screwdriver, remove the two
    clips that hold the air filter in place, and pull the filter and neck assembly off the bike. It is not required to remove the
    whole air filter, but I find it easier to get it off the bike instead of messing with the rubber neck in the way of the carb.
    You can also remove the carb from the engine and leave all the cables attached, but I wanted the carb off the bike as
    well so I left it attached to the intake manifold.
Remove the throttle cable from the carb throttle arm by manually opening the arm to release the slack, and then pushing
the end nipple out of the guide. The whole cable can then be pushed back through the adjuster.




Use an adjustable wrench to loosen the clutch plunger. Pull the plunger out of the carb body and tuck it away in the
frame so it is out of the way.




Depending on the clip you have on the carb end of your fuel line, either loosen it with a flathead or squeeze the two
ends of the clip together to get the fuel line off the carb intake. Make sure the fuel valve is turned off before removing
the line.
Locate where the electrical wires come out of the engine on the top side of the fan housing and follow them back to the
junction box on the frame arm. Write down how all the connections are made and then unplug the engine side from the
junction box.




Once disconnected follow the wires back and make sure they are free from the frame. Typically you'll have to thread
them back through the fuel tank clamps to get them free.




Remove the single fan shroud bolt that holds the ground wire in place just in front of the rear wheel. This completes all
the left side disconnects, and we can move on to the right hand side.
The right hand side connections are the spark plug, the gear cables, the clutch cable, and the rear brake cable. Start by
removing the spark plug lead from the plug. Follow the control cables along the upper side of the engine casing and
you'll find the gear and clutch connections. Use a 3.5mm allen key and a xxmm wrench to stop the nipple from turning
to loosen all the nipples and then pull the inner cables through and free. Note that the far nipple on the gear selector
block is taller than the others.




Move back to the adjuster block and pull the inner and outer cable through the adjuster block. Stuff the cables
somewhere away from the engine or use a zip tie to hold them all out of your way.




Find the rear brake adjuster just inside the rear hub. You can either disconnect the rear brake at the foot pedal under the
floorboards, or remove the adjuster from the end of the cable as I did.
Using two wrenches, loosen the single bolt that connects the cable to the adjuster. You may have to fully remove the
bolt to get the adjuster free.




With the adjuster free, straighten the cable so it can be pushed back through the lower shock support casting...




...and push the entire cable back and clear from the engine casing.
Remove the 24mm nut and washer on the upper and lower shock mounts. Once removed you may find that the shock is
hard to get off. The trick is to pull each end just a small bit at a time so it comes squarely off the mounting posts. Once
off the rear wheel will be able to hit the inside of the rear mudguard.




At this point you may want to wedge a milk crate, car jack, or something else between the ground and the rear of the
bike. This will make removing the engine a little easier especially if you are doing this on your own.




Remove the center 24mm nut from the main pivot point bolt. Sometimes the entire bolt can rotate instead of just the nut,
so you may need a second wrench on the other side to get the nut off.
Only one nut needs to come off but the pictures show both nuts removed. Using either a punch to the center of the bolt,
or a block and hammer start pounding the pivot bolt out of the engine mounts. The block or punch is used so that the
threads are not damaged. Once the bolt is flush with the mount I like to use a flathead screwdriver and hammer to keep
pushing the bolt through. This is a nice trick because once the first mount is free the screwdriver will not allow the
engine to completely drop out.




With the bolt fully removed, do a final check for anything else that may still be connected. If everything is clear,
remove the screwdriver holding the engine in place and lower the engine to the ground. It is easiest to have a friend help
lift the bike off the engine but if you are alone then you will have to work the engine out of the frame by pulling the rear
wheel out to the left.




Once the engine is free you can move on to rebuilds, crank removal, and other projects that are much easier with the
motor on a bench.
    Installing a Lambretta Drive Side Oil Seal & Bearing
    The drive side of a Lambretta has one large main bearing and a single oil seal to stop the gasoline/air mixture leaking in
    to the transmission and visa/versa. The following steps are from a Lambretta GP 200 but can be adapted to most
    Lambretta models starting with the Series I bikes. The images show a stripped GP 200 block with all the components
    removed. You'll need:
             One new drive side bearing (FAG 6305.C3).
             One new drive side oil seal.
             New drive side seal washer.
             4 M6 x 1.00 thread by 20mm long allen drive cap head machine bolts or 4 Phillips head M6 x 1.00 by 20mm.
             4mm allen head driver or large Phillips screwdriver.
             Thread lock.
             A blow torch.
             A hammer and drift or a series of washers and bolts to draw the bearing in to the casing.
             Some high melting point grease.
    The best thing to start is to freeze the drive side bearing. Freezing metal just causes it to slightly contract. It is nothing
    you can see or feel but it will make putting the parts together much easier.




    Keep it frozen until you need to install it. Check the new main bearing to make sure it is spinning freely.
Oil seals are made from plastic around a metal core. They have a lip that has a circular spring around the outside face.
This spring is what causes the seal to work because it puts pressure around where the crank passes through the center.
The shot above shows the lip slightly pulled back to show the circular spring. Typically the spring goes to the side that
has any pressure. In a Lambretta engine that side is always facing towards the crank due to the primary compression
that happens as the piston falls in the bore.




The easy way to get the bearing in to the aluminum casing is to heat the casing and feeze the bearing. This shrinks the
bearing and expands the casing just enough to make installation easier. Since there are no oil seals or gaskets in this
casing you can heat it up with a blow torch until water sizzles on it. You will need a large socket or large thick washer
with a pipe or block of wood to pound the bearing in to place. Make sure that the washer or sockets only makes contact
with the outer lip of the bearing which is past the ball bearings themselves. If you make contact with any of the rotating
parts you could damage them as the bearing is hammered in.
Start hammering the bearing in from the crank side. Make periodic checks on the transmission side to be sure the
bearing is hit all the way in. The shot above shows it only partially in the bore. There should be no space between the
shoulder of the bearing and the aluminum casing.




If the bearing is unusually stubborn you can make an easy tool to draw it in to place with washers and bolts from your
local hardware store. Basically find two washers (1) with a diameter large enough to cover the trasmission side bearing
hole, and (2) to cover just up to the edge of the bearing on the crank side. Find a bolt and pass it through the center and
start cranking away. In the shot above I used a second washer becasue the hole in the main washer was too big for the
bolt nut.
Once you are happy that the bearing is all the way in, take a break and let the casings cool before installing the oil seal
as noted below.
The main oil seal is an easy fit in to a metal flange which is then bolted in place. The flange has two distinct sides and
can only be installed with the countersunk screw holes side facing out towards the crank. The oil seal is set into the hole
in the center. Again, the spring goes towards the crank and the seal is fitted from the other side of the flange. The seal
can be pushed in place with just your fingers.




Here's a shot of the seal fitted in to the flange from the drive side. The face of the seal should be as flush as possible
with the backside of the flange.
And here's a final shot of the flange with the oil seal fitted from the crank side. The next step is moving on to fitiing the
flange to the casing itself.




Grease up the drive side bearing with high melting point grease. Clean the bolt holes the best you can .
The next step is to fit the bearing washer. This is a weird washer which is more like a gasket than a washer. It can be fit
in either direction, but make sure the edges are down against the bearing edge as shown below.




Once it is seated well it is time to mount the drive flange with the oil seal. On original motors there are 4 Phillips head
screws that are approximately 16mm long. I find these a bit of a pain to tighten without the head of the Phillips
screwdriver jumping out. An alternative is to use cap screws with an allen head drive.
I also also found that the thread holes are deeper and can easily accept a 20mm cap screw which are very common and
easy to find. To be sure this was not some weird issue with my motor casings, if you use 20mm screws/bolts try
inserting them in the holes first to make sure you don't run out of thread. When you finally put them in for good, use
thread lock on the threads before you insert the cap screws. If these ever come out they will immediatley rub against the
side of the crank web and start filling your motor with metal filings which destroy everything. If you are really worried
about them you can side punch each cap screw to stop it from rotating.




First tighten the scews until the start to get tight, and then work your way around turning about 1/4 trun at a time until
you can't turn them anymore.
    Above is a final shot of the bearing and drive seal in place. Make sure the flange is flush with the casing all the way
    around where the red and blue arrows meet
    Next Section -->



    Removing a Lambretta Flywheel
    The flywheel helps the engine idle properly, has an integral fan, and rotates magnets around the stator to produce AC
    power. To remove it you'll need:
           A Lambretta flywheel puller
           A Lambretta flywheel holder
           A 17mm socket & driver
           Two adjustable wrenches
           A flathead screwdriver




    Remove the left hand side panel to get access to the motor. Then remove the screws holding the fan shroud to the
    engine casing. I seem to remember this can be done without removing the left side floor board extension, but these
    pictures are of a motor not currently in a frame so I could be mistaken.
Once the shroud is removed the center cover and the flywheel are visible. The center cover is held in place by a wire
retaining ring. Squeeze the two ends together and the ring can be removed.




The center cover has slotted ears and may have to be rotated around until the ears align with slots in the flywheel before
it can be removed.




Using a flywheel holding tool and a socket and driver, loosen the 17mm central nut. Remember this is a left hand
threaded nut which means it operates in the reverse way as a normal nut. Rotating it clockwise actually loosens it.
Remove the nut and the shake proof washer. Make sure all the internal threads are clean before fitting the puller.




Carefully thread the puller in place. Be sure to get it nice and deep in the bore so that you have more thread to pull
against. Sometimes it is necessary to use the flywheel holding tool to get the puller nice and deep.




Use adjustable wrenches to tighten the center part of the puller and keep the outside from turning. You should hear a
pop when the flywheel is pulled off the tapered end of the crank.
    Carefully lift the heavy flywheel clear of the casing. If you feel some resistance it is likely to be the magnets on the
    flywheel trying to pull towards the steel on the coil supports. Once the flywheel is clear have a look in the slot in the
    crank taper for the woodruff key. Sometimes it will be stuck in place and can be left but if it is loose, take it out and
    save it for the rebuild (or just use a new one).




    With the flywheel out of the way the stator is accessible for maintenance or replacing entirely.




    Installing a Lambretta Flywheel Side Bearing & Oil Seal
    The flywheel side oil seals and bearings are made up of many parts and in Series III bikes all the models are the same
    except for the GP200. The GP200 crank has a wider crank shoulder but uses the same mag side flange casting. The
    following steps are from a Lambretta GP 200 (with the LI/SX/TV differences shown) but can be adapted to most
    Lambretta models starting with the Series I bikes. The images show a stripped GP 200 block. You'll need:
            New bearing: NU2205E for GP200, NU205E for LI/SX/TV
            New outboard oil seal: 25x42x6
            New inboard oil seal: 33x52x6
            New circlip (or reuse the old one)
            New spacer washer (or reuse the old one)
            New inboard spacer (LI/SX/TV only)
            A blowtorch
            A mallet and drift (or large socket)
            High melting point grease
            Circlip pliers
Above is a shot of the components that go into the mag side flange of the GP200 engine. From left to right is (1) the
main circlip, (2) the inboard oil seal, (3) the outer race of the main bearing, (4) the spacer, (5) the outer oil seal. The LI,
SX, and TV series bikes differ because of a thinner flywheel side bearing. Due to this difference, another spacer is used
in between the inboard oil seal and the bearing (this will be covered in the intsallation steps below).




Above is a shot of the LI style crankshaft with a new flywheel side bearing. The bearing is a two part assembly. The
outer part with the rollers in it goes into the cast aluminum mag flange. The inner part fits on the crank shaft itself. You
will need to remove the previous race if it is still on the crank. I took mine down to San Francisco Scooter Center who
pulled it off for me (thanks guys) because they are such a pain to get off. If you don't have access to the correct tool to
remove it or don't have access to a scooter shop it can be done by heating it up and using vice grips, or carefully cutting
it off but I don't recommend these approaches.
Once the old race is off the new one can be pushed out of the two part bearing ready to be installed.




The mag flange is a handy base to use to get the inner race on. You can set the crank with the drive side down as a
convenient holder.
Heat up the inner race on the end of a screwdriver by using a propane torch. The heat capabilities of a propane torch
don't really have the ability to damage the race but will make it expand slightly and allow it to drop onto the crank.




Once the race is hot it can be dropped down the flywheel side taper. If it is nice and hot it will drop down all the way to
the crank web oil seal lip which is where it should be. If it doesn't go all the way down, remove the crank from the mag
housing temporary support and support the flywheel side crank web before tapping the race down with a long tube and
hammer. Do not tap it down without supporting the crank web or you could risk damaging the crank.
Now that the inner race is on we can move back to the mag flange. The outboard oil seal is the first to be put in place
from the inside face of the mag flange. Above is a shot from the crank side of the mag flange. There is a small circular
spring around the lip of the oil seal. This must face towards the crank once installed. The mag flange can be heated to
ease the placement of the seal but you'll probably have to touch it with bare fingers to get the seal in so don't go heat it
beyond what you can touch.




It is important that the seal seats nice and flat against the lip in the mag flange. Above is a shot from the flywheel side
of the mag flange showing the seal correctly orientated and seated.
The mag side parts include a spacer washer that keeps the oil seal in place as there is a gap between the seal and the
bearing (which will be installed next). This should go with the flat side towards the seal and the lip towards the bearing.




The outer race with the roller bearings needs to be installed in the mag housing. At this point you'll need to heat the mag
flange with a blow torch to ease the bearing installation. Be sure to keep the flame away from the recently fitted oil seal
and make sure not to heat the casing beyond about 200 degrees F or damage can happen to the seal. To make
installation even easier freeze the bearing before installation. Use a drift or large socket to bang the bearing in to the
mag flange, but if you do make sure the socket edge only makes contact with the outer rim of the bearing. You'll notice
a difference in the sound once it is fully home.
LI/SX/TV Only: Since the LI/SX/TV range has a thinner flywheel side bearing but uses the same mag side flange, a
little space is necessary between the bearing and the oil seal. As far as I can tell, this can go in either way up as shown
above.




The inboard oil seal is fitted next, again with the spring and lip towards the crank. This seal is a bastard to fit but be
patient and slowly force it in by hand. If required you can use a flat piece of wood to carefully bang it in place.
The last two steps are to fit the circlip retaining ring and grease the bearing. Make sure the clip doesn't get caught up on
the oil seal. Smear high melting point grease all around the bearing. This bearing is not lubricated by the gasoline/oil
mix so the grease is its only lubrication.
That's it. Let's move on to the crank installation page.

Installing a Lambretta crank
The Lambretta crank is a pretty cool design. It just clears the casing when installed and has to go in at a funny angle just
to fit properly. The crank below is from a GP200 and it was fitted just as a test so it does not have the mag side flywheel
race installed on the crank.
Freezing the crank before installation is a neat trick that makes installation much easier. Just throw it in the freezer for a
few hours before you install. The reason is that metal shrinks just slightly when cold and so the close tolerances of the
bearing and the crank shoulder have more play. It is also useful to have a crank installation tool to pull the crank
shoulder through the drive bearing.




Above are three shots of how the crank is installed. Click on each image to get a larger view of each step. The first step
is to grease the single drive side oil seal and bearing so that the seal is not damaged during installation. If the motor is
out of the bike, set it so that the mag side flange opening is facing up.
(1) Turn the crank to bottom dead center so that the crank pin is furthest from the crank mouth.
(2) Bring the crank down at an angle so the small end of the con rod fits through the left side main crankcase transfer.
(3) Align the drive side of the crank with the bearing hole and give it a good push. Do not use a hammer to get the crank
further into the bearing. Since there is a pin at only one side of the crank, if you try and use a hammer you'll end up
possibly bending the crank and having to replace it later.
    The crank installation tool is then placed on the drive side of the bearing and a bolt is threaded into the drive side shaft
    of the crank. Holding the crank with one hand, tighten the bolt and the crank will slowly be pulled through until the
    shoulder hits the bearing. This tool is cheap and available from MB Developments.




    The crank shoulder never seems to come all the way flush with the side of the bearing but a quick look inside the engine
    shows that the crank web is almost touching the oil seal flange. I'll update this page if I have any problems with this
    installation.




    Piston Install
    One of the most important parts of a well operating engine is a good piston and bore to keep compression high and
    transfer that power to the back wheel. Basic tolerances between a piston and a bore are typically 0.2mm. If you remove
    your barrel and find deep scoring on the piston and bore it is definitely time for a new piston. Pistons cost between $45
    and $70 depending on what bike you are buying for. Whenever a new piston is installed it is important to rebore the
    barrel to the next oversize if there is major scoring of the surface, or at least hone it to be sure that the wear ridge at the
    top is removed. The one pictured is from a GP125 motor. The following images show the piston replacement after
    removal of the old barrel and piston, and in these images the engine is out of the frame but it is not a requirement.
             A piston kit
             A rebored or honed barrel
             Some two stroke oil
             A new barrel base and head gasket
             Circlip pliers
             Possibly a new small end bearing (optional)
             A set of feeler gauges
             A 14mm socket and driver
A piston kit usually comes with the piston, two new rings, a wrist (or gudgeon) pin, and two circlips. On the piston
above you can clearly see an arrow stamped in the top facing to the left of the image. When the piston is installed this
must be facing the exhaust.




Step 1 - Checking the ring gap: Take either one of the rings and fit it as squarely as you can in the top of the barrel
bore. When the rings get hotter they expand and it is critical to be sure there is enough room for expansion otherwise
there is risk of a seizure. With the piston ring in the bore, slide the ringless piston down in the bore skirt first. This will
push the ring down in the bore and keep it square to the diameter of the bore. I usually push it down until the wrist pin
hole is about central with the top of the barrel.
Remove the piston and get out a set of feeler gauges. The minimum ring gap is 0.2mm. Measure this gap by fitting a
feeler gauge in between the ring ends while making sure the ring is not in any port windows. If it is less than this you
will need to remove the ring and use a very fine file or sandpaper to slightly increase the end gap. If it is more than this
you may need to buy new rings for your piston. Once you are happy with the gap, slide the piston down as you did
before and push the ring through the bore to remove the ring. Check the second ring in the same manner.




Step 2 - Preparing the piston: Before the piston is installed, the rings must be put on the piston. Both rings are the
same so it doesn't matter which one goes on first but it does matter which side faces "up". Have a look at the piston ring
grooves and you'll see small peg in each groove shown with the green arrow above. The peg is not central to the groove
and is set closer to one edge so that only half the peg circle extends into the groove. Now have a look at the ends of a
piston ring. If you slightly compress it with your fingers you'll see that the same half circle space is cut out of the ring
ends.




Make sure you have the piston ring the right way up for the groove you are setting it in. Carefully stretch open the ring
so it can fit over the piston and slide it down the sides until it fits the groove. I usually fit the lower ring first as it is
harder to get the lower ring over and already installed upper ring. Do a final check to make sure both rings fit well and
their ends interface with the pegs.
Above is a shot of the lower ring correctly installed for reference. Fit the upper ring in the same manner.




Step 3 - Installing the piston: Fit a new small end bearing or (on older models) a brass bushing. Use a little two stroke
oil to lubricate it. The images above are of an engine which is actually upside down from the way it would be installed
in a bike as it is easier to work on and balances itself on the engine mounts. Please keep this in mind when following the
steps if your engine is still in the bike.
Look on the piston head for an arrow stamped in it. This MUST face towards the exhaust port or directly down towards
the ground in a motor still mounted in a bike.




Before fitting the piston you may need to heat it with a hot wet rag to allow the wrist pin to fit more easily. Press the
wrist pin in only far enough that it stays in place and then take the entire piston assembly and center the wrist pin hole
over the small end hole. Carefully push the wrist pin through the caged needle roller small end bearing and through to
the other side of the piston. When fitted correctly both sides should have an equal depth from the pin end to the face of
the piston.
Using circlip pliers, fit both circlips to either side of the pin. Make sure they are fully seated in the groove in the piston.
You don't want these coming loose in a running engine. Since this picture was taken I have learned more info and all
circlips should be installed so that they have the ends either up towards the piston head or down towards the piston
bottom, that way there is no way for the clip to get squeezed by the accelertion of the piston, and pop out.




Step 4 - Installing the barrel: Slide a new base gasket over the piston. This gasket will only fit one way due to the
cylinder studs.
Clean and check the bore for any dust or any other contaminate. Rub some two stoke oil around the bore for lubrication.




Carefully start to slide the barrel on to the cylinder studs. The barrel can only fit one way and goes on with the spigot
(the part that sticks out past the fins) towards the casing. Once the spigot has come down on the piston enough to hit the
first ring, you'll need to compress the ring to get it into the barrel.
Make sure that if the rings have rotated, their ends are back in line with the ring pegs. Carefully compress the rings with
your fingers while sliding the spigot down over the piston. Once one ring is in the barrel you can switch to the second
ring and use the same idea. Slide the barrel all the way down over the piston and turn the flywheel to make sure the
piston travels freely in the bore.




Once the barrel is in place, and has been pushed down on to the casing, you can install the single aluminum head gasket.
This only fits one way due to the cylinder stud layout.




Fit the head to the cylinder studs...
    ...and add the washer and nut to each stud. A single stud (shown in the next picture with a green arrow) receives the
    special coupler nut that the barrel cowling bolts into. Tighten the nuts only hand tight for the time being.




    This image has been flipped to show how the head looks if the motor is installed in the frame. Tighten the head nuts
    about 1/2 a turn each and then alternate to the next one in the pattern shown above. This system makes it very unlikely
    to warp the head when tightening. The green arrow shows the location of the coupler nut.
    Finally, fit the spark plug, cylinder shroud, and start the motor up.

    Note: For the first 300 miles you should drive very carefully, do not over rev the motor, stay at low RPMs where
    possible, and vary the engine RPM when stuck in any single gear because of road conditions. Breaking in a piston
    carefully is the best way to ensure long life from your top end.
    A typical new piston with new rings and a rebore should develop about 125 to 140 PSI compression which can be tested
    with a spark plug threaded compression tester available from most auto parts stores.

    Clutch Plate Replacement - Lambretta
    A Lambretta Series 1-3 has very good access to the clutch and can have the cork plates replaced without having to split
    the main crank case. A few signs that your plates need replacing are that the bike's RPMs increase faster than the speed
    of the bike (especially when going up a hill), your kickstart is having trouble turning the engine over when it engages
    properly, and a basic lack of power.
    Some tools and items you'll need:
             A 10mm allen wrench
             Either an adjustable wrench, 21mm wrench, or a 21mm socket and driver
             Basic metric socket and driver
             About 1 1/4 pints of SAE 30 oil with a funnel or hose attachment to the container
             Oil drain pan
             new cork clutch plates with a small soaking dish
             new chaincase gasket
             clutch compressor - about $15 from WCLW
    Start by getting the bike on level ground and setting it on the kick stand. The clutch is driven by an enclosed chain and
    runs in a bath of transmission oil in the right hand side of the engine casing.
    Step 1: Remove the right hand side rear foot board. This is done by removing 3 nuts that are accessed from underneath.
    Two of the bolts heads are cast into the plastic outer runner at either end and one bolts the small frame bridge piece
    down to the floorboard. These are all shown with arrows below. The plastic encased bolt heads have a tendency to spin
    if the bolt threads are rusty..I still haven't worked out a way to stop this from happening.




    Step 2: Drain the oil. For step by step instructions see the Lambretta oil change page.
    Step 3: Remove the exhaust. The exhaust is held on by 2 bolts to the face of the chaincase, 1 bolt into the bottom of the
    main casing, 1 bolt just below the oil drain plug, and a final bolt and compression bracket connecting it to the U-Bend
    exhaust tube from the engine. All these must be removed to take the exhaust off. Some of the bolts are shown below
    with arrows.




    Step 4: Remove the chaincase. Now you should have a clear view of the chaincase. The clutch cable must be removed
    from the actuating arm and can be done by simply unhooking it from the arm. If you are unsure where the clutch arm is
    just pull the clutch lever and you'll see it move. Remove all the 10mm (I think) nuts that are around the chaincase
    perimeter. Once these are all removed the chain case can be pulled off.




    The clutch will now be clearly visible and needs to be compressed before you can remove the old plates for
    replacement. The only way I have found to successfully do this with a minimum amount of swearing is to buy a
    specialized tool for the job. This tool literally takes less than a 2 minutes to attach and safely compresses the clutch -
    highly recommended!! It simply bolts to 4 of the chaincase studs and then a handle can be turned by hand. I left the
    little clutch actuating cap in place as it rotates as the compressor is tightened while leaving the clutch basket in place
    (see (1) below) Once the clutch is compressed remove a small retaining clip which runs all the way around the inside lip
    of the basket (see 2 below). The plates can now be removed and replaced. Take careful notice of the order of the plates
    and be sure to replace them in the order they were removed.




    There are two types of plates in the clutch - plain metal ones with a smooth outer circumferences and a tabbed inner
    hole and ones with small segmented patches of cork on their faces and notched metal tabs around the circumference. It
    is rare that the bare metal plates will ever need to be replaced unless the clutch has become very hot at some time and
    warped them. The cork plates should be soaked in transmission oil before being installed as dry plates have a tendency
    to grab until they have absorbed oil.




    This quick guide assumes that you are not replacing the clutch springs - I'll add info on that when I need to do it to my
    bike. Re-assembly is the reverse of the disassembly. With new plates you may need to adjust the clutch cable with the
    small adjuster fitting on top of the main crankcase.

    Next Section -->

    Removing a Lambretta crank
    The Lambretta crank is a pretty cool design. It just clears the casing when removed and comes out only at a funny
    angle. This section assumes you have already removed the flywheel, barrel, piston, and the gearbox side crank gear and
    cush-drive. You'll need:
            10mm socket & driver
            A small flathead screwdriver
            A rubber mallet
            Two 6mm bolts approximately 1 1/2" or longer
First, scribe a line between the stator and the casing to align the stator when you rebuild. This will mean that you won't
need to do any timing adjustments when rebuilding (assuming the timing was correct to start with). Remove the three
10mm bolts (arrowed) which hold the stator plate in place and the stator will come loose. Look on the top side of the
mag housing and you'll see where the stator wires exit the casing. Unscrew the two small flathead screws to release the
wires and pull the whole stator off the casing.




Remove the three 10mm nuts (red arrows) and washers which hold the mag flange to the main casing. The mag flange
is a very tight fit in the casing and the flange will not come off with only these nuts removed. The blue arrows show two
threaded holes which are used to force the mag flange away from the main casing.




Insert two 6mm bolts into these holes and tighten them both equally by hand until they stop. Then start by tightening
each one a full turn and then switch to the other and do a full turn. This will force the mag side off squarely in relation
to the main casing.
If you look underneath the engine while you are doing this you'll see the mag flange start to separate from the casing.




Once the bolts have pushed the flange far enough, you'll be able to fully remove the mag side flange and inspect the oil
seals and bearings for wear. Discard the gasket between the two pieces as you should always use a new one when
rebuilding.




Flip the engine over and locate where the crank end is visible through the main bearing. Turn the crank to bottom dead
center (BDC). BDC is when the big end of the con rod is closest to the rear wheel so that the amount of con rod visible
past the crank web is the shortest. This is important as it is the only way the crank will fit out of the main casing. Once
you have the crank at BDC, gently tap the end with a plastic or rubber mallet, or a hammer using a block of wood to
protect the end of the crank.
    Once the crank starts to move back through the main bearing, be sure the con rod is moving into the left hand side
    transfer space and not jamming on the casing. Once the bearing side is free the whole crank needs to be rotated out of
    the casing around the con rod axis. This will make more sense once you get to this step.




    The crank should now be free and can be inspected for wear or completely replaced.




    Removing a Lambretta Drive Side Oil Seal & Bearing
    The drive side of a Lambretta has one large main bearing and a single oil seal to stop the gasoline/air mixture leaking in
    to the transmission and visa/versa. The following steps are from a Lambretta Li125 Special but can be adapted to most
    Lambretta models starting with the Series I bikes. The images show a partially stripped Li block most components
    removed. You'll need:
             An impact driver with a flathead bit
             Possibly a drill with a 1/8" bit
             Possibly a blowtorch
             A hammer and large socket or wood block
    The drive side seal plate is held in place by four annoying screws. To make matters more fun each screw has been
    punched at the edge to stop them rotating. You can see the punches at the end of each flathead slot in the dirty shot
    below.
An impact driver is an imperative tool to remove these screws. The way the driver works is by translating the force of a
hammer blow into a rotational force on the bit. What makes it very useful is that since you hit the top of the tool, it will
turn the screw, but most of the force is downwards and keeps the bit in the screw slot.




Above is a shot of an impact driver I got from Sears for $19.95. It comes with many heads and has a square 1/2" drive
so it can be used with big sockets too. If you try and use a flathead screwdriver to remove the drive plate screws you are
very likely to mess the heads up and make them far more difficult to remove, and possibly ruin the block. Also an
extension is sometimes a good idea, as you can see that the large part of the driver can hit the mag side flange face and
mark it.
The screws in this particular block showed no signs of moving even with the impact driver. I used a drill with a 1/8" bit
to drill out the punch mark and help the screws be able to rotate freely. This will usually mean a new drive plate should
be used because you will be drilling into both the screw edge and the drive plate. After drilling the punch marks, I
heated the casing witha blowtorch to release the grip on the screws.




Using the impact driver the screws finally began to turn!




Once all the screws are removed, the drive plate and oil seal can be removed from the casing. There is also a small
gasket like washer that goes in between the moving part of the bearing and the oil seal. It is usually stuck to the
backside of the drive plate. Both the seal and the washer should be replaced.
Using a large socket as a block, hammer the drive bearing out from the outside face of the casing. Heat up the casing
around the bearing with a blowtorch before you bang it through.




The bearing will then drop out of the crank side of the casing and can be cleaned, inspected, and possibly replaced.




The oil seal is a press fit in the drive plate. To remove it simply push it out towards the back side of the plate away from
the face with the countersunk holes in it....
    ...and it should push right out.

    Installing a Lambretta Drive Side Oil Seal & Bearing
    The drive side of a Lambretta has one large main bearing and a single oil seal to stop the gasoline/air mixture leaking in
    to the transmission and visa/versa. The following steps are from a Lambretta GP 200 but can be adapted to most
    Lambretta models starting with the Series I bikes. The images show a stripped GP 200 block with all the components
    removed. You'll need:
             One new drive side bearing (FAG 6305.C3).
             One new drive side oil seal.
             New drive side seal washer.
             4 M6 x 1.00 thread by 20mm long allen drive cap head machine bolts or 4 Phillips head M6 x 1.00 by 20mm.
             4mm allen head driver or large Phillips screwdriver.
             Thread lock.
             A blow torch.
             A hammer and drift or a series of washers and bolts to draw the bearing in to the casing.
             Some high melting point grease.
    The best thing to start is to freeze the drive side bearing. Freezing metal just causes it to slightly contract. It is nothing
    you can see or feel but it will make putting the parts together much easier.




    Keep it frozen until you need to install it. Check the new main bearing to make sure it is spinning freely.
Oil seals are made from plastic around a metal core. They have a lip that has a circular spring around the outside face.
This spring is what causes the seal to work because it puts pressure around where the crank passes through the center.
The shot above shows the lip slightly pulled back to show the circular spring. Typically the spring goes to the side that
has any pressure. In a Lambretta engine that side is always facing towards the crank due to the primary compression
that happens as the piston falls in the bore.




The easy way to get the bearing in to the aluminum casing is to heat the casing and feeze the bearing. This shrinks the
bearing and expands the casing just enough to make installation easier. Since there are no oil seals or gaskets in this
casing you can heat it up with a blow torch until water sizzles on it. You will need a large socket or large thick washer
with a pipe or block of wood to pound the bearing in to place. Make sure that the washer or sockets only makes contact
with the outer lip of the bearing which is past the ball bearings themselves. If you make contact with any of the rotating
parts you could damage them as the bearing is hammered in.
Start hammering the bearing in from the crank side. Make periodic checks on the transmission side to be sure the
bearing is hit all the way in. The shot above shows it only partially in the bore. There should be no space between the
shoulder of the bearing and the aluminum casing.




If the bearing is unusually stubborn you can make an easy tool to draw it in to place with washers and bolts from your
local hardware store. Basically find two washers (1) with a diameter large enough to cover the trasmission side bearing
hole, and (2) to cover just up to the edge of the bearing on the crank side. Find a bolt and pass it through the center and
start cranking away. In the shot above I used a second washer becasue the hole in the main washer was too big for the
bolt nut.
Once you are happy that the bearing is all the way in, take a break and let the casings cool before installing the oil seal
as noted below.
The main oil seal is an easy fit in to a metal flange which is then bolted in place. The flange has two distinct sides and
can only be installed with the countersunk screw holes side facing out towards the crank. The oil seal is set into the hole
in the center. Again, the spring goes towards the crank and the seal is fitted from the other side of the flange. The seal
can be pushed in place with just your fingers.




Here's a shot of the seal fitted in to the flange from the drive side. The face of the seal should be as flush as possible
with the backside of the flange.
And here's a final shot of the flange with the oil seal fitted from the crank side. The next step is moving on to fitiing the
flange to the casing itself.




Grease up the drive side bearing with high melting point grease. Clean the bolt holes the best you can .
The next step is to fit the bearing washer. This is a weird washer which is more like a gasket than a washer. It can be fit
in either direction, but make sure the edges are down against the bearing edge as shown below.




Once it is seated well it is time to mount the drive flange with the oil seal. On original motors there are 4 Phillips head
screws that are approximately 16mm long. I find these a bit of a pain to tighten without the head of the Phillips
screwdriver jumping out. An alternative is to use cap screws with an allen head drive.
I also also found that the thread holes are deeper and can easily accept a 20mm cap screw which are very common and
easy to find. To be sure this was not some weird issue with my motor casings, if you use 20mm screws/bolts try
inserting them in the holes first to make sure you don't run out of thread. When you finally put them in for good, use
thread lock on the threads before you insert the cap screws. If these ever come out they will immediatley rub against the
side of the crank web and start filling your motor with metal filings which destroy everything. If you are really worried
about them you can side punch each cap screw to stop it from rotating.




First tighten the scews until the start to get tight, and then work your way around turning about 1/4 trun at a time until
you can't turn them anymore.
    Above is a final shot of the bearing and drive seal in place. Make sure the flange is flush with the casing all the way
    around where the red and blue arrows meet

    Lambretta Series III Gearbox
    A Lambretta Series 1-3 has a gearbox that is basically located almost in the rear wheel hub. There are many small
    differences between models, and this page shows a Series III gearbox removal and installation.
    Some tools and items you'll need:
            2x 6mm bolts at least2" or so long to remove the backplate.
            Either an adjustable wrench, 21mm wrench, or a 21mm socket and driver
            Basic metric socket set and driver.
            A rear wheel puller.
            New rear wheel bearing, gear cluster bearing, axle end caged bearing, and rear wheel oil seal.
            Gearbox shims in several thicknesses.
            Circlip pliers.
            Rubber mallet or a hammer and wood block.
            A set of feeler gauges.
    This page also assumes that you have the chaincase off, the clutch removed, and the rear wheel removed.




    The first step is to remove the gearbox backplate. Use an 11mm socket to remove the six nuts arrowed with red and the
    six lock washers around the perimeter. Unfortunatley once these are removed the plate will not come off because it is a
    tight fit on the end of the gear cluster shaft. The solution is to use two 6mm bolts and insert them into the green arrowed
holes above. Slowly and equally tighten each one to force the backplate away from the casing. Soon the backplate will
be able to be lifted off exposing the gearbox parts inside.




With the backplate out of the way you can gain access to the free gears and the gear cluster and selector spider. There is
a single shim for the free gears which can be removed and kept for safe keeping (red arrow above). The one in the shot
is very worn with a clear groove around the inside.




Now the free gears can be removed from the axle. Be sure to note which way each gear faces when you remove them as
they need to go back in the same orientation. It is handy to stack them in the right way and put a zip tie through them to
be sure they will go back the same way later. You may need to slightly rotate the gears on the shaft to allow them to be
lifted off.
Remove the small gear cluster and watch out for a small shim where the green arrow is pointed. This may stick to the
bearing in the casing or to the gear shaft. You can also remove the other caged bearing at the end of the free gear axle
and the small end shim beneath it. Either renew these items or hold on to them for the rebuild. The gear spider is a little
tricky to remove. I found that pulling up on it hard is a good way to remove it from the rear axle. Be warned that there is
a single spring and two ball bearings which may shoot out from the interior of the shaft so use a rag to stop them
shooting out. The actuating arm of the selector will stay in the casing for now.




With the gear selector spider removed, the gear axle can be removed by banging it out of the rear bearing. I usually put
an old nut on the axle to protect the threads from any damage. At this point you can also decide to replace the rear
bearing and oil seal if you want to (I did). To remove the rear bearing, the four bearing retaining nuts, locknuts, thick
metal retaining plate, and thin sheet metal spacer need to be removed from the rear hub area of the engine casing. Then
the bearing and oil seal can be pounded out from inside the casing in the direction of the rear hub. I had my brake shoes
off at the time the photo was taken but it is not required to remove them.
Remove the arrowed bolt with a 10mm socket which releases its grip on the gear selector splined shaft.




The gear actuator arm can only be removed from inside the casings by removing the external gear selector splined shaft.
This exits the casing right by the rear wheel. Pull the splined shaft out of the internal actuating arm by lifting upwards
and you should hear the actuator fall into the casing inside. Your actuator may be a two piece assembly like mine or a
single piece as fitted to later models.
While you have the parts out and the gearbox open, you might as well replace all the items that wear and cause gear
selector problems, or allow the bike to jump out of gear. Above is a shot of a new spider on the left and a used spider on
the right. You can see the rounded over ends to the spider which can cause the bike to slip out of gear when riding. Also
have a look at the contact points where the spider hits the free gears to see if each gear is in good condition.
Now we'll start rebuilding the gearbox. I rebuilt mine into brand new casings and I replaced all shims, bearings, and the
spider.




The first step is to replace the rear bearing. The bearing has an oil seal that prevents gearbox oil from leaking out into
the rear hub and ruining the brake shoes. This seal goes into the stepped bearing on the side with the larger step (if you
look at the bearing you'll see what I mean). The side with the circular spring in the lip faces the smaller side of the step
(it faces towards the gearbox).
Put a little grease around the inside lip of the seal and push it into the bearing race. Once it is in properly the bearing
will not spin as freely as it used to because of the friction. It should look like above.
Now the bearing can be fit into the casing. It is especially important to be sure the bearing is set into the casing as far as
it will go, although it will never be flush on the hub side. The reason for this is that later you will be looking for a very
specific tolerance between the free gears and the gearbox back plate. This tolerance can be adjusted for wear by fitting
gearbox shims that range in thickness from 2.0mm to 2.6mm. If the rear wheel bearing is not fully installed tight against
the casing, this gap will end up too large for standard shims to fill.




Start by heating the casing a little with a blowtorch. This will expand the aluminum and make the bearing fit in more
easily. Fit the bearing with the stepped side towards the casing and the oil seal visible from the outside. Use a hammer
and a large socket or a flat plate - be sure if you use a socket it rests on the outside rim of the bearing. Bang it in until it
will not move in any more.
Once the bearing is tight against the casing you can install the single thin sheet metal plate, and then the thick metal
retaining plate. The thick retaining plate has a small curve to it. Make sure the curve is facing the bearing, fit the four
lock washers and nuts, and tighten them down.




Flip the casing over so you can get to the gearbox side and start installing the components. I start with the rear axle shaft
without the spider installed, but some people like to install the spider first on a work bench and then install the complete
unit as one. Have a look at the rear axle before you install it and you will see that there is a hole drilled all the way
through in the splined sections where the free gears run. Mark its location for later when the spider is installed. All you
need to do is fit the axle and give it a few taps from a hammer and wood block, or a rubber mallet and it should go right
in. Make sure it is in as far as it can go by checking that the axle is tight against the rear bearing.
The way the spider stays where it should when you are driving is by a single spring and two ball bearings on either end.
The spring runs through the hole in the axle you marked earlier and the ball bearings are forced into notches on the
spider legs. As you change gear, the spider starts to move, the ball bearings are forced against the spring, and then they
pop back out into the next notch in the spider leg. The bottom side of the spider has two legs that are bevelled unlike the
others. These are to aid installing it over the bearings which are trying to move out.




To fit the spider you first need to set the spring into the axle hole, and the two ball bearings on either end. Use a little
grease if necessary to hold them in place.
Place the spider on the shaft making sure the bevelled leg ends are in the same grooves as the ball bearings. Then push
down hard and it should compress the ball bearing spring and drop firmly in to place. I always leave the spider in the
first gear position for reasons that are clear later on if you have an all in one external actuating arm. This means that the
spider legs are flush with the thick part of the axle as shown above.




The selector arm can now be loosely fitted to the spider. It has two small rotating blocks on the end, which slide into the
groove in the spider. Make sure the arm is installed so that the single bolt hole has the threads towards the rear hub.




On the outside of the casing above the rear wheel, slide the gear selector splined shaft into the casing. With one hand
inside, make sure the shaft goes into the selector arm hole. Depending on your model, the selector arm may be a single
piece but the one on this casing is a two piece unit. If it is a one piece unit you should probably fit the rear hub to make
sure the gear selector arm doesn't hit the rear hub rim when the bike is in first gear. If it is a two piece like the one
shown above, the arm will be adjustable and you can fit it so it doesn't hit the rear wheel before you complete the
rebuild.
Once you are happy with the placement of the gear arm on the outside of the case, fit the single selector arm bolt and
tighten it down with a socket. I move the spider through the gears at this time to make sure each one selects properly.




The small roller bearing (red arrow) can now be fit into the casing followed by a small gear cluster shim (green arrow)
and the gear cluster itself. There is a special tool to remove the metal outer which is a press fit into the casing, but
unless the play between the new roller bearing and the outer is obviously suspect, it is easier to leave it in place. I also
found a difference between my new Indian casings which came with this piece installed, and my old Li125 Special
casings. The new casings had a small lip which set the gear cluster further off the casings. I was worried this would
misalign the free gears and the gear cluster but it ended up not being a problem. After asking a few questions I found
that once the clutch is installed the gear cluster shaft is pulled tight to the gearbox end plate anyway, and doesn't really
ride against this lip - the bearing is just there to locate it and spin.
Now start adding the free gears in the same direction you took them off. Make sure each gear interfaces well with the
gear cluster. You may have to rotate them slightly to drop down over the shifting spider.




Fit first gear with the kick starting ring facing you. This is followed by a new axle bearing shim, and the new roller
bearing at the end of the shaft. Once these are all installed, fit the single large gearbox shim which fits in the groove at
the inside of the first gear piece (not shown installed, but it goes where the blue arrow notes). This shim may need to be
replaced later with a thicker one, but unfortunately the only way to tell is to build the gearbox and then measure the
tolerance.
    The gearbox backplate has a pressed fit ball bearing which supports the end of the gear cluster. Have a look at your
    bearing and see if it worth it to you to replace it. Since I was building a non-stock motor I replaced mine to be safe. To
    replace the bearing, remove the retaining circlip and bang the bearing out from the other side with a suitable sized
    socket. To install the new one, flip the backplate over and bang the new one in until it is flush with the inside lip. Refit
    the circlip and the back plate is ready to install.




    Before fitting the backplate make sure you have remembered the small roller bearing at the end of the rear axle shaft,
    and the important gearbox shim. Then carefully lower the backplate into position and push it down until you can see
    enough thread on the six casing studs (green arrows) to get the nuts started. Fit lock washers to each stud and then add
    the nut. Start tightening the nuts one at a time and only about a turn at a time. You are trying to set the backplate down
    so that the backplate bearing is forced onto the gear cluster in a level manner. As you tighten the nuts check to make
    sure the backplate is moving equally down on each side and that it is not racking in one direction or another.
    Once it is fully down, tighten all the nuts and either fit the rear hub and tighten it fully down, or fit a small spacer tube
    instead of the rear hub and also tighten it down. This is required because it makes sure the rear axle is absolutely tight
    against the bearing, so you can get an accurate reading of the shim tolerance noted below. Now get a set of feeler
    gauges to measure the tolerance between the backplate rim and the gearbox shim. Be sure you are getting the feeler
    gauge right in against the backplate rim where the red arrow is shown above. Anywhere between 0.30 and 0.07mm is
    within tolerance. If it is beyond this range you will have to remove the backplate and fit a thicker shim. Unfortunately
    the only way to measure the tolerance is with the backplate totally torqued down, so this may be a frustrating process. I
    usually have a couple of difference thickness shims on hand (these can be ordered from your scooter shop), and once I
    make the first measurement, a little math can work out the one you need.

    Kickstart Disassembly
    One of the most important parts of a well operating engine is a good piston and bore to keep compression high and
    transfer that power to the back wheel. Basic tolerances between a piston and a bore are typically 0.2mm. If you remove
    your barrel and find deep scoring on the piston and bore it is definitely time for a new piston. Pistons cost between $45
    and $70 depending on what bike you are buying for. Whenever a new piston is installed it is important to rebore the
    barrel to the next oversize if there is major scoring of the surface, or at least hone it to be sure that the wear ridge at the
    top is removed. The one pictured is from a GP125 motor. The following images show the piston replacement after
    removal of the old barrel and piston, and in these images the engine is out of the frame but it is not a requirement.
             A piston kit
             A rebored or honed barrel
             Some two stroke oil
             A new barrel base and head gasket
             Circlip pliers
             Possibly a new small end bearing (optional)
             A set of feeler gauges
             A 14mm socket and driver
The shot above shows an SX200 chaincase with the kickstart in place. The way the system works is that there is a metal
guide held in place by three bolts which retracts a small "shoe" plunger in the end of the kickstart shaft when the
kickstart is at rest. When pushed the guide allows the springloaded shoe to extend which messhes with teeth in the face
of the first gear cog. Only one of these bolts is fully accessible when the kickstart is at rest.




Start by removing the bolt on the guide that you can see without moving the kickstart.




Once the single bolt you can see is removed use a block of wood to wedge under the kickstart on the outside of the
casing. This will allow the heads of the other bolts to be exposed.
Remove the remaining two bolts and the metal guide will come away from the chaincase. Be sure the block stays in
place because if it slips the shoe plunger will return very quickly.




Once the guide is removed carefully remove the block and let the plunger & show return to the previous location.




Now flip the casing over and remove the kickstart from the spline. Before removing it is a good idea to mark the shaft at
the point where the split in the kickstart pinch is so that you can put it back in the same place. While removing it make
sure you have a helper holding the shoe so that it doesn't suddenly spring back.
Use circlip pliers to remove the single clip over the kickstart spline. Also remove the single small washer beneath it.




The spline should now be able to be lightly tapped through the casing.




Remove the oil seal and replace it when rebuilding. The easiest method is to pry it out with a screwdriver.
Remove the spring by pulling the bottom end pin out of the hole in the casing (arrowed).




There is also a brass bushing under the oil seal which can be replaced if really worn, but I skipped that process on this
chaincase.



Carb cleaning
When gasoline sits for a while in a scooter it turns to a yellow goo that clogs filters, jets and fuel
taps. All these items should be removed and cleaned and the fuel tank should be drained and refilled
with clean gasoline.
The tank on this bike was (amazingly) very clean and only needed draining. The fuel tap can be
removed with a wrench from the base of the gas tank. I took apart the fuel tap to be sure it was not
clogged. The main brass housing can be removed from the rotating fuel tap by clamping (lightly)
the tap body in a vise and unscrewing the rotating assembly. Be sure to check that the filter and all
the passage ways are clean by blasting it with compressed air or carb cleaner. I replaced the fuel
line because the gasoline had changed to a solid sun tan cream consistency as shown below.
I removed the rubber air supply bellow from the carb and found that someone had become very
frustrated with this carb in its former life. The intake face had been hammered flat and the
identifying carb text had been flattened. The inside face of the venturi was also scared badly - while
I don't think any of these items will affect the final engine performance too much, as none of the
passageways are fouled, a new carb body would be recommended.




Cleaning a carb is an easy process and requires taking it completely apart. Buy a bottle of carb
cleaner preferably with a small tube to attach to the aerosol head for tight areas and blasting out
air/fuel passages. Be sure to have an assortment of various sized screwdrivers and some smaller
metric wrenches. The brass jets are fragile and can be damaged by using the wrong sized
screwdriver. Start by unscrewing every possible part of the carb and soak them all in a dish full of
carb cleaner.
Below is a shot of all the parts in a Lambretta Series III carb, cleaned and ready for re-assembly.
Blow through all jets with compressed air or use a straw with a pen cap as a tip and blow through
them with your lungs.




The jets and airways of a carb a very important to keep clean and free of debris. There are two
filters in the fuel system to keep gas clean. One is located in the intake on the fuel tap and the other
is where gas enters the carb. Both these should be checked to be sure they are clean.
Below is a quick overview of the jets in a Series III carb. The jets are brass and only the main jet
and atomizer are screwed together as a single unit. Gasoline enters the carb and is drawn directly
into the float chamber. Inside the float chamber there is a ball-cock assembly similar to a toilet tank
on a small scale. It stops the gasoline from being able to flood the venturi tube and upset the air/gas
mixture. With the gasoline supply stemmed by the float the jets can suck up gas from the float
chamber where it is mixed with air in the venturi and then makes its way into the crankcase.




The jets all have small text to identify them. The jet size is very important in a carburetor and the
incorrect jet can produce an engine that can run roughly or even hole a piston. Jet sizes are listed for
both Vespas and Lambrettas on the model pages.

Next Section -->
    S p e c s: LI 125 Series 3
    1961 - 1967
    amount produced: 146,734
    engine: single cylinder, air cooled 2-stroke
    induction: piston ported
    bore: 52 mm
    stroke: 58 mm
    cubic capacity: 123 cc
    compression ratio: 7.0: 1
    bhp at rpm: 5.5 @ 5,200
    transmission: 4 speed constant mesh
    primary drive: 46/15 (early)
    1st gear: 17.40: 1
    2nd gear: 10.71: 1
    3rd gear: 7.47: 1
    4th gear: 5.65: 1

    primary drive: 46/15 (late)
    1st gear: 13.95: 1
    2nd gear: 9.67: 1
    3rd gear: 7.04: 1
    4th gear: 5.65: 1
    lubrication: 2%
    carburetor: Dell'Orto SH18
    choke: 18 mm
    slide: 5914/1
    atomizer: 5899/1
    main jet: 99
    starter jet: 50
    pilot jet: 42
    ignition: contact breaker & points
    ignition timing: 23 deg. BTDC
    breaker gap: 0.35-0.45 mm
    voltage: 6 volt
    wheels: 10"
    wheel hubs: cast
    tires: 3.50 x 10
    max speed: 45 mph
    total dry weight: 229 lbs
    click for li125 series III electrical page


    Lambretta Fork Bearings
    The main clue to whether you may need to replace your fork bearings is a shudder while braking from higher speeds.
    This may also be caused by the front brake shoes or an ovaled hub, but a distinct shudder is usually due to the fork
    bearings failing, or at least the securing nuts may be loose. Either way here's how to remove and replace the fork
    bearings.
    The following instructions are for a Series III bike, but Series I and II are pretty much the same.
    You'll need:
            An Allen head socket set or other driver
            A small flat head screwdriver
            A large flat head screwdriver
            A headset retaining ring removal tool (or a flat head screwdriver & mallet) or some vice-grips.
            Grease.
            A large adjustable wrench
            Something to set under the bike to get the front wheel about 18" off the ground.




    The first step is to remove the headset top and headlight to get to the fork tube pinch bolt. Unlike Vespa, Lambrettas
    have the pinch bolt inside the headset with no access from the outside. Unscrew the four small screws that hold the
    chrome hexagonal ring to the headset top and bottom. The headlight can then be removed if you want it totally out of
    the way, or just remove the upper two and loosen the lower two which will give the ring enough play to get the headset
    top off. The bike shown here is an Li125 Special Series III (similar bodywork to a TV175 and SX150). If you have an
    Li you will need to remove the three screws around the headlight chrome ring instead.




                                                                         Â
    The next step is to remove the headset top and disconnect the speedo. Remove the two screws (one on each side) from
    the underside of the headset to allow the top to be removed. The speedo cable will hold the headset top down - don't try
    and pry it up! Locate the point where the speedo cable is connected to the front wheel, and feed it upwards as much as
    possible. This should allow the clearance needed to lift the headset top, reach in, and unscrew the speedometer cable
    from the speedo unit as well as pull out the single speedo bulb. The headset top should now lift off.
You can either move all the wiring to one side, or disconnect it all from the headlight block. Make sure you keep a good
record of where it all plugs in for the rebuild. Once everything is out of the way, you'll see the single Allen head pinch
bolt which keeps the headset connected to the fork tube. Loosen and fully remove the Allen head bolt and shake proof
washer.




Since the brake cable on a Lambretta does not run through the forks you can simply unscrew the large circular adjuster
(arrowed).




Once the adjuster is removed, push the threaded part back through the arm, and disconnect the brake cable from the
casting in the brake hub.
Grab the levers of the handlebars and twist from side to side while holding the front wheel in between your feet. As you
do this, lift up and the headset should start to rise up and off the fork tube. Most bike will have enough length in the
electrical and control cables to allow you to get the headset off the tube and fold it back without disconnecting anything.




If you have the correct tool for this job it is by far the best way to loosen the retainer. I don't have one so I use a flat
head screwdriver and hammer to loosen the top retainer. It unscrews just like a normal nut.




After the first retainer, there is a single washer with a small peg which slots down a groove in the fork tube. Remove it
and check the peg is in good condition. If not, replace the washer.
The final retainer can be removed with a large wrench. Make sure the front wheel is supported if your center stand lifts
it off the ground. It is harder to loosen this nut with gravity pulling the forks down.




As the last retainer comes off, the caged bearing is visible in its groove. Once the retainer and bearing race are out of the
way the forks can be dropped out of the bottom of the bike, along with the speedo cable.




To drop the forks, place blocks under the center stand to get the front end high off the ground. You can also remove the
rear shock to drop the rear of the bike even further. As the forks drop out another larger bearing race will be visible
under the front mudguard.
I happened to have my front wheel off in the shot above, but it is not necessary if you are just removing the forks. This
shot was also before the blocks under the center stand to get the forks clear of the bike.




With the forks out of the bike, you can either rebuild them, repack the old bearings with grease, or replace the bearings
completely. Inspect the surfaces that the bearings run in and clean them up with a solvent to remove the old grease, and
steel wool to remove any surface rust. If the bearing races are pitted or badly rusted they should be replaced (you'll have
to look in the service manuals for how to do it as this bike didn't need them replaced).
When reassembling the forks into the frame, make sure all the bearings are well greased. Always use the both retaining
nuts with the pegged washer in between. This effectively makes a locked nut system so that it cannot loosen while you
are riding. When tightening the first retainer with a wrench make it tight enough so the forks can't rock about, but loose
enough so that when the wheel is off the ground, the forks will fall to the left or right from center if given a little tap on
the front wheel. Make sure you use a shake proof washer when reinstalling the pinch bolt. Before the headlight is
installed do your best to make the headset point straight when the front wheel points straight. Tighten the pinch bolt and
quick test drive will let you know if you are aligned before reinstalling the headlight & headset top. If not you can easily
make small adjustments by loosening, but not removing the pinch bolt.

Lambretta Disk Hub Disassembly
Lambretta was the first of the Italian scooters to add a disk brake to a production model. The first disk brake was fitted
to the TV175 and then was also adopted by all the other Lambrettas 175ccs and up.




The original disk brake was cable operated and had a static inboard pad and a operable outboard pad. The disk in the
center of the hub was able to slide on three pins and the outboard pad would push the entire disk until it was clamped
between the inboard and outboard pad. Click here for an exploded view of the parts involved
The first step is to remove the front wheel from the forks as shown in this page. Once the hub is free, disconnect the
speedo line and the front brake cable so that the hub can be placed on a workbench
Remove the nut from either side of the main axle.




This is then followed by a flat washer. These should be kept or replaced on the rebuild.




Note that the washer has a raised collar on the inside face which seals against a grease seal in the hub.
Remove the (very crusty) disk actuating arm cap by prying it off with a small flathead.




Using a set of circlip pliers, find the ends of the clip (arrowed) and ....




...remove the retaining clip.
The whole arm system should then lift out, although it may be stuck due to lack of use. Try a solvent to free it up if it is
really loose and you plan to replace the disk pads anyway. DO NOT use a solvent if you are going to reuse the pads as it
will ruin their effectiveness. The disk arm on my bike was blasted clean and greased up before reassembly. The way it
works is very simple using ball bearings to force the actuating plate out when the arm is pulled.




If you are planning on painting or powdercoating the hub you'll need to remove all the parts from it. Remove the small
grease nipple from the speedo drive with a wrench. My cables were in such bad shape I simply cut the front brake cable
because it was jammed in the hub...that's why it still shows in the picture.




Remove the drive shroud with a small wrench or socket. The drive shroud should then pull free from the hub.
..followed by the actual drive itself. Look at the drive teeth to make sure they are in good condition.




Now it is time to remove the main axle. On this hub the axle nuts will be replaced so I used the old one to protect the
axle threads as I banged the axle out (arrowed). Support the hub on wooden blocks and always drive the axle out from
the disk brake window side of the hub.




This is the reason to drive it out from the disk window side. There is a small lip on the axle on the fixed hub side.
The hub will not separate even with the axle removed, because the disk is still held by the caliper. To split the side of
the hub you need to carefully push the entire disk towards the fixed hub side. As you'll see in a moment, the disk can
move along three central locating pins. This is so one side of the disk can have a static pad. To remove the disk from the
locating pins, remove the disk windows by carefully prying them out with a screwdriver. Once they are out, rotate the
disk window side of the hub so that you get two windows over the disk itself.




Using a block of wood, and supporting the hub, carefully tap the disk along the locater pins. Do a few taps on one side,
then switch to the window directly across from it and do the same amount of taps there. This should stop the disk from
getting skewed on the locating pins. You may need to use WD40 or something similar if the pins are rusted.




Once the disk is free the hub should come apart. Check the speedo drive gear to make sure the teeth are in good
condition. Also you can clean up the three locator pins with steel wool if they are rusty.
Above is the sad looking very rusted steel disk used in the Lambretta disk hub. A quick blast with glass beads cleaned it
right up and there was very minimal pitting.




The fixed hub side still has the fixed pad and the moving pad fixed in the caliper. Also check the thin rubber seal in the
main axle hole and replace if cracked or obviously failing.




Using a block of wood, flip the hub over and find the moving disk pad which is in the hole where the disk actuator arm
was removed.
A few taps and this should drop out of the hub. These are cheap parts and your life could depend on them so if in doubt
replace them with new ones. The part number for both is 19744200 and you'll need two.




The static pad has a small adjuster shaft and lock nut. Remove these (mine came off in one) and set aside. If yours
comes off in one, use a vice and an Allen wrench to separate them as they are used to adjust the disk brake in the future
when the hub is put back together.




Using a small punch, tap out the static pad until it drops into the caliper and out of the hub.
The last step it to remove the bearings if you plan to replace them or have the hub painted or powdercoated (if
powdercoating you'll need to remove the plastic speedo drive too or it will melt). Using circlip pliers remove the clip on
the disk window side of the hub.




Flip the hub over and remove the small spacer which has a recessed part to seal against the grease seal.




Pry out the grease seal. and be sure to replace it with a new one during the rebuild. Be careful not to damage the speedo
drive while levering it out.
With the grease seal out of the way, support the hub window side down, and use a socket or block of wood to tap the
bearings out. The window side bearing should start moving as there is a tube spacer between the two bearings.




With these removed, the hub is now ready for cleaning, blasting, and painting or powdercoating. In both situations if
you are not doing it yourself, make sure that all the areas that have moving parts or threads are covered well and make
sure you painter knows what to paint and what not to. Scraping paint or powdercoating off a hub is a pain in the ass.

				
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