Workshop - Engine and Gearbox

Details for this section are for the Lambretta 175 Li Series 1 and 2 however there are many similarities between these models and other models of Lambretta threewheelers/Lambros. This information and the pictures included are provided from the 'Instructions for Repair Shops' for these models published in 1963. It is intended for informational purposes and we would recommend seeking professional advice before undertaking anything described in the Workshop section.

Dismantling and Reassembly

Dismantling Engine/Gear Box group from Frame.


To remove seat base: open the seat base, draw out the two split pins holding the hinge pins, remove the pins and detach the base.


For 1st series only - To release choke cable: with­draw the split pin on starter lever pin on engine, remove the thrust washer, then the pin.


To remove carburettor controls:
Close petrol tap, remove petrol pipe, unscrew choke and remove, release throttle cable, open the clip on carburettor hose and remove hose.


To remove gear box controls:
Pull back protection hoses at gear cable ends, put gear in neutral position, remove allen screws (3.5 mm allen key) on trunnions holding cables to selector lever, withdraw cables from trunnions and remove trunnions from lever.


To detach the reverse gear control cable:
Uncover trunnion (Part No. 41032002) by drawing protection hose back, unscrew grub (3.5 mm allen key) on trunnion, withdraw cable and grommet on support. Take care not to lose the top hat on cable.


To detach clutch cable:
Rotate lever, remove cable fixing trunnion on the lever, unscrew cable tensioner and withdraw cable through cut on tensioner support.


To detach wires from flywheel pick up:
1st Series : Unscrew the two 8mm nuts fixing junction box on frame transverse beam under the seat, remove the two washers and box cover and pull out the Brown and Green wires from junction box.
For 2nd Series : Withdraw the three wires (two yellow and one green) connecting flywheel to electrical circuit.


To remove H. T. Cable from Spark Plug :
Remove the spark plug cover, unscrew the right hand screw on plate holding grommet on flywheel flange, remove H. T. Cable.


To remove engine earthing wire:
Unscrew nut on stud joining crankcase to gearbox and withdraw earth lead terminal from stud


To remove exhaust:
Unscrew the two screws fixing flywheel cowl, remove screws fixing cylinder head cowl (14 mm spanner), withdraw the cowl, unscrew the two nuts on exhaust tube flange (11 mm spanner) remove tube from studs, remove exhaust gasket.


To detach transmission coupling:
Remove hose clips holding dust protector hose at gear box end, and slide back hose.


To remove engine/gearbox group :
Unscrew the three bolts (10 mm spanner) fixing engine supports, remove the three upper support cups and buffers, pull out engine group.
It is not necessary to dismantle the elastic transmission coupling.

To reassemble engine/gear box group on to the frame, reverse the above operations.


Removing Engine from Frame without Gear Box


Carry out operations:
1st Series: Nos. 1, 1b, 2, 5, 6, 7, 8, 9
2nd Series: Nos. 1, 2, 5, 6, 7, 8, 9


To drain oil from Crankcase: place a tray under the gear box, unscrew drain plugs, one under the gear box and the other in the rear gear box cover.


To detach engine from gearbox: unscrew the nuts fixing engine to gear box and remove the washers.


To remove the engine supports: unscrew the three screws on each of the two supports (10 mm spanner) remove the upper caps and buffers. Remove the engine, taking care not to draw forward to avoid damaging the two engine/gear box dowel pins

To reassemble engine : Reverse the above operations


Removing Carburettor from Engine

16 Carry out operation No. 2.
17 Loosen screws fixing carburettor clips, (8 mm spanner) slide carburettor from the induction pipe.


Removing Gearbox from Frame

18 Carry out operations 1 to 11
19 Drain oil as indicated in operation No. 13.
20 Detach engine from gear box as per operation No. 14.
21 Remove gearbox: pushing slightly backwards to avoid damaging the engine/gear box guide dowel pin

To reassemble gear box to frame reverse the above operations.


Dismantling of Engine


Remove engine from frame as per operations 12-13-14-15 and clamp on to vice by the short engine support arm (See Fig. 1).


Remove carburettor as per operation No. 17.


Remove flywhel fan cowl by unscrewing the 5 screws (8 mm spanner),


To remove flywheel Dust Cover: unscrew the two screws fixing this to the flywheel or remove the circlip holding the cover according to type fitted


To remove flywheel: lock flywheel with tool 580131 unscrew flywheel locking left hand nut, (17 mm socket and tool No. 62751) extract flywheel with appropriate extractor (Tool No. 37059). See Fig. 2.


To remove Stator Plate : If the timing is correct, it is advisable to mark the position of the stator plate in respect to the flywheel support flange, so as to facilitate the timing at reassembly.

Remove screw on left hand side of cable grommet plate, (the right hand screw having been removed in operation 7), remove the plates and grommets, drawing grommet from cable. Take care with the gasket.

Unscrew the three screws fixing plate to mag housing and remove stator plate (10 mm spanner). Extract the stator plate, sliding leads out of sheath through hole in mag housing.


To remove cylinder head : unscrew the four nuts fixing head (14 mm socket and tool No. 59943). Remove washer, withdraw head and gasket.


Remove cylinder. (See Fig. 3).


To remove piston : remove the gudgeon pin circlip, withdraw pin, using a push pin or tool. Remove piston rings.
On 1st series engines, the small end bush is in bronze. 2nd series engines have a needle roller small end bush.


To remove the mag housing, unscrew the three fixing nuts (10 mm socket) and extract the flange using tool No. 49188, fixing this to the housing by means of two of the stator plate bolts.


To remove drive side spocket: lock crankshaft with tool 49221, placed on connecting rod, unscrew bolt fixing damper (14 mm socket), remove washer, spring, the sliding sleeve and sprocket, then extract sleeve by means of tool No. 60051, remove oil thrower Part No. 19012041 (See Fig. 5).


To remove crankshaft: tap with a copper mallet from the gear box end, so that it slides out of the bearing.


To remove the main bearing inner race: use Tool No. 63703 (See Fig. 6). This operation can be carried out with crankshaft still fitted, after having removed flywheel flange (operations 24-25-26-27-31) (See Fig. 7).

Note : The two parts forming the roller bearing are not interchangeable. In case of damage or wear, it is necessary to change the complete bearing.




To remove roller bearing outer ring from flange: remove circlip locking the inner oil seal, remove distance piece, heat flange in oil to 150"C and extract bearing outer ring (Tool 59331). Care must be taken not to damage the oil seal.

Avoid carrying out this extraction cold because the tolerance between flange and bearing outer ring is so tight that extracting cold could damage the seating.


To remove drive side ball bearing: unscrew the four screws fixing the bearing locking flange, remove flange, insert tool 65420 into the inner oil seal, and by tapping tool with mallet remove bearing. In the absence of the correct tool, use a bearing puller or gently tap bearing out with hammer and socket.


Reassembly of Engine

Reverse the above operations, and carry out the following operations:


To replace drive side ball bearing on crankshaft: fit bearing, aluminium washer and oil seal on to the screw of tool 59329. (Check first if oil seal is in good condition, otherwise substitute the group No. 41012008, and take care that the seal support ring is in contact with the bearing). Put tool screw into the bearing seat, then fit on to the screw the 73 mm diameter disc, with its lowered face towards the bearings, and then the distance piece. Screw nut to distance piece, holding screw with 12 mm spanner.

In the likely situation that you do do not have this tool, freezing the bearing causes it to shrink slightly making it much easier to fit.

Check that the fitting of the bearing is carried out axially and perpendicularly perfect, and adhering at every point, i.e. with the oil seal flange and seat.


To replace the flywheel side roller bearing outer ring: Ensure that the bearing seat in the flange is not damaged. If so, replace flange.

Check if the oil seals are in good condition, if not, replace. It is however, always advisable to change oil seals when overhauling. Heat up flange to approximately 100"-150"C and fit the small oil seal, the cup washer, with the cupside towards the bearing, and the bearing outer ring, the distance ring and the large oil seal. Freezing the bearing outer ring will also help in this operation. Then fit circlip. Before fitting bearing and flange to shaft, fill chamber between oil seals with special grease.


To refit the roller bearing inner race to the crank­shaft: Place shaft in a vice by its flywheel end. Slide the inner race on to the shaft. Tap the race with punch No. 59331, having care to keep the race well aligned on the shaft. (It is generally the rule to warm the inner race in oil before fitting to the shaft). TIP: Putting the crank in the freezer for 15 minutes will make this process much easier


To tighten the drive side bolt: if the piston has not been fitted, lock crankshaft with Tool 49221 between the two shoulders. If the piston is fitted, the tightening of the bolt should be left until operation No. 26, when the tool can be used to lock the flywheel


To replace cylinder and piston in the case of substitution of one or both; bear in mind that the cylinder and piston have been paired according to the four grades. These are marked 1, 2, 3, 4, stamped on the top of the cylinder and the crown of the piston. For the correct pairing, cylinder and piston must be of the same grade.

When refitting the piston, it is absolutely necessary that the piston ring pins in the ring grooves face the exhaust port of the cylinder; therefore the arrow marked on the crown of the piston should point towards the exhaust side. If the piston is fitted the wrong way, the rings will break up as soon as the engine is started.


When fitting piston into cylinder, use piston ring clip Tool No. 53213.


When refitting exhaust pipe, take care that the gasket 19018001 is placed in the correct position. Tighten the exhaust tube flange nuts correctly and equally (11 mm spanner),


Dismantling of Gear Box

The dismantling and reassembly of the gear box parts can be carried out with the gear box in a vice, as shown in the following illustrations.
It is necessary however to prepare a support similar to that shown in Fig. 21 which should be applied to the crankcase in substitution of the rear side anchoring arm.


Check that the gears are in neutral.


Remove gear box from frame - operations 18-19­20-21.


To remove the front elastic joint, remove the three nuts (14 mm spanner) holding the rear transmission shaft yoke arm. Remove the bolts and slide off the yoke arm fitted with splined sleeve, remove rubber protection ring and the split pin. Remove nut on shaft (27mm spanner) and slide the front yoke arm off. Take care of the oil seal (No. 41030073) (see Fig. 8).


To remove the rear gear box cover: remove the four huts and the two screws fixing the cover to the gear box (10 mm spanner), remove washers, and cover, taking care not to damage the three guide pins, then remove the gasket (See Fig. 9). Take care of the shim washer (41030081) on the reverse gear shaft (No. 41030071) (another shim is placed at the end of the shaft, the distance piece (41030072).


(On vehicles fitted with speedo). - Remove speedometer drive by unscrewing the bolt fixing it to the gear box casing.


To remove the reverse gear group and shaft: lower the reverse gear lever, and withdraw the group, gear, shaft and lower gear with chain, (Be careful with the needle bearing in the lower gear ond the shim. (See Fig. 10) Remove the sleeve, moving this sideways to extract it from control fork and lifting the fork itself, then remove the needle bearing on the shaft. Remove the shim and extract the control fork. (See Fig. 11).


To remove gear at exit: insert tool 63427 which will lock the gear, remove layshaft nut with 21mm socket, remove washer, withdraw and remove the gear (See Fig. 12),



To remove clutch plates: Apply tool No. 62329 to press the clutch springs, remove circlip with the help of a screwdriver, loosen the tool central screw, re­move discs, the flange holding the springs and then the springs. (See Fig. 13) TIP: It is possible to adapt a standard Lambretta Clutch Compression Tool with the addition of some nuts and bolts and a small plate with two holes!


To unscrew the internal clutch bell locking nut; free the nut from its locking washer, lock clutch bell with tool 59804 (standard Lambretta tool) and unscrew nut fixing it to the primary shaft (22mm. socket).


To remove the inner and outer clutch bells; place tool 59328 on to the bell, refit the circlip and extract the inner bell, withdraw the sprocket which is part of the outer bell, the needle bearings and shims, (See Fig. 14).


To remove the gearbox end plate: Unscrew the six nuts fixing it to gear box (11 mm socket) and extract the plate using the two threaded holes. Use 6mm screws and help the extraction with a screwdriver between flange and crankcase making leverage on case edge. Take care with the needle bearing and secondary gear shims.


Withdraw the gears from the lay and primary shafts (See Fig. 15).


To withdraw secondary shaft: Tap shaft with mallet from reverse gear end and withdraw it with gear shifter sleeve still fitted, rotating the gear control inner lever. Take care with the distance piece.


Pull off the sliding dog from the layshaft taking care not to lose the two balls and springs.


To remove the secondary shaft bearing: remove the two circlips and with the punch No. 59330, remove bearing by tapping the punch.


To remove the outer race of the needle bearing on the primary, use appropriate tool No. 59350.


Reassembly of Gear Box

Reverse the preceding operations, paying particular attention to the following:


To refit the primary needle bearing outer race: first slide the end shim washer and then fit the outer race tapping it in place with an appropriate punch.


To refit the layshaft ball bearing: use punch tool No. 59330 to tap the bearing into its seat from the reverse gear side of the gear box.


To refit the main gears to the layshaft, this must be done as follows :

- The fourth gear must have the high part of its boss facing the clutch end of the gear box.
- The third gear must have the high part of its boss facing the reverse gear side of the gearbox.
- The second gear must have the bight part of its boss facing the reverse gear side of the gearbox.
- The first gear must have the front dog teeth facing the clutch side of the gearbox.

A faulty assembly of the gears will bring about the breaking up of the teeth as soon as the gear change is operated when running. After the gears are fitted, replace the shim Part No. 19030023. Check when the flange has been fitted, that the axial play between the group of gears and the shim must only be between 0.3 and 0.07 mm. (0.0118" to 0.0027").

When refitting the flange ensure not to damage the centering dowels.


When refitting the reverse group upper shaft, ensure that its end pin coincides exactly with its seat in the hub in the crankcase.


Dismantling the Kick Start Group


Remove engine from frame following operations 12, 13 14, 15.


For 2nd Series only - To remove kick start pedal Unscrew and remove the pedal fixing bolt (11mm. spanner), remove the washer and draw pedal from its shaft. Be careful with the shim.


2nd Series only - To remove kick start cover: Unscrew the four screws fixing cover to crankase, remove the cover, and gasket with care (See Fig. 16).

56 2nd Series only - To remove quadrant (Part. No. 41010068). Remove the circlip, unscrew quadrant boss bolt: (12mm spanner) remove washer and draw quadrant from shaft. (See Fig. 17).
57 2nd Series only - To remove quadrant (Part No. 41010069), Remove the Bolt fixing the quadrant (12mm spanner) and its washer, draw out kick start pedal shaft and remove quadrant. Pay attention to the shims on each side of the quadrant boss (See Fig. 18).



To remove start shaft.
1st series Rotate start lever to end of its stroke and keeping it in this position, remove lever stop buffer support (14rnm spanner) and the cam (10mm spanner), unload spring by freeing the hand lever slowly. Remove circlip from lever, remove fixing bolt and draw off the lever, the circlip washer, starter shaft and the spring.

For 2nd Series Block shaft in vice between two lead plates, or insert the kick start pedal on to the splined end of the shaft, locking it with a 4mm nut and bolt of the right length. (The second method is more suitable if the engine has not been completely re­moved). Load the spring so as to have a rotation of the shaft sufficient to remove the cam (10rnm spanner) and with the shaft held still in the corresponding position, by unscrewing locking bolt (12 mm spanner) the return stop buffer can then be removed; slide starter shaft axially so as to permit, when passing over the buffer support plate, the necessary rotation to unload the spring. Remove shaft and spring (See Fig. 19).


To remove starter shaft position:
Place shaft in vice, unscrew reference pin, remove the circlip, the disc, the spring and then the pin. (At the original assembly the reference pin thread has been burred over to avoid loosening).


Reassembly of Kick Start Group

To reassemble, reverse the above operations, paying particular attention to the following:


Refit the shaft piston: as mentioned previously the pin thread has been burred over to avoid loosening. When refitting the pin to the piston, check the condition and, if necessary, replace with a new one.


Refit starter shaft to crankcase:

For 1st series : Refit K/S pedal return spring ; place tool 57776 on the end of the shaft to avoid damaging the oil seal on the case, push shaft into its boss in the case, and remove the tool 57776. Fix the shaft in position by fitting the washer and circlip. Fit the hand lever to the shaft, load the spring by rotating the shaft to the end of its movement, and replace the stop buffer; then, keeping the shaft in the same position, refit the cam.

For 2nd series : Replace the return spring on to the starter shaft. Slide shaft into the crankcase and the end of the spring into its anchoring hole in the case. The shaft is not to be pushed home in full to allow it to overcome the buffer support plate.
Place the splined end of the shaft in a vice with lead jaw plates, or fit the pedal to the splined end fixing it with a 4 mm bolt.
By rotating the shaft, load the spring, passing over the stop buffer support plate.

(Ensure that a spiral of the spring does not slip in between the boss in the crankcase and the starter shaft collar).

Slide the shaft axially into the crankcase until its collar touches the boss in the case. Fit the stop buffer. Load the spring by rotating the shaft and holding it in the desired position fit the cam. Release the shaft or free the pedal.


Adjustment of Starter Cam

The cam for the starter piston must be blocked in such a position so that with the shaft at the end of its full return position

a) The top of the piston's front tooth is level with the starter shaft cylinder.
b) The piston can still move no less than 1.5 mm towards the outside of the cylinder.


Dismantling of Reverse Gear Control from Gear Box


To remove the flanged hub and the lever remove the nut (14 mm socket), the washer, the hub and the lever, then the spring (See Fig. 20).


To remove the quadrant; remove the external circlip and the washer. Slide quadrant shaft from inside, paying attention to the internal pin 41031021 pushed by spring 41031019, and to the shim 19031015 in contact with the quadrant hub (See Fig. 21).

Reverse the above operations when reassembling.

Dismantling of the Gear Control from Gear Box


To dismantle rocker arm and quadrant, remove nut locking quadrant (10 mm socket), withdraw rocker lever and quadrant (See Fig. 22).


To remove gear control shaft: remove outer circlip and screw fixing selector fork (9 mm spanner), then the inner circlip 83160100, and slide shaft out. Pay attention to the internal shim, the felt ring, and the outer shim ; remove internal control lever 1903100 (See Fig. 23).