VESPA S 50 4T 4V (2008), 2008 S 50 4T 4V User Manual

MANUALE STAZIONE DI SERVIZIO

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Vespa S 50 4T 4V (2008)

MANUALE

STAZIONE DI

SERVIZIO

Vespa S 50 4T 4V (2008)

The descriptions and illustrations given in this publication are not binding. While the basic specifications
as described and illustrated in this booklet remain unchanged, PIAGGIO-GILERA reserves the right, at

any time and without being required to update this publication beforehand, to make any changes to

components, parts or accessories, which it considers necessary to improve the product or which are

required for manufacturing or construction reasons.

Not all versions/models shown in this publication are available in all countries. The availability of single

models should be checked at the official Piaggio sales network.

"© Copyright 2008 - PIAGGIO & C. S.p.A. Pontedera. All rights reserved. Reproduction of this publication

in whole or in part is prohibited."

PIAGGIO & C. S.p.A. - After-Sales

V.le Rinaldo Piaggio, 23 - 56025 PONTEDERA (Pi)

MANUALE STAZIONE DI

SERVIZIO

Vespa S 50 4T 4V (2008)

Questo manuale per stazioni di servizio è stato realizzato da Piaggio & C. Spa per essere utilizzato dalle
officine dei concessionari e sub-agenzie Piaggio-Gilera. Si presuppone che chi utilizza questa
pubblicazione per la manutenzione e la riparazione dei veicoli Piaggio, abbia una conoscenza base dei
principi della meccanica e dei procedimenti inerenti la tecnica della riparazione dei veicoli. Le variazioni
importanti nelle caratteristiche dei veicoli o nelle specifiche operazioni di riparazione verranno
comunicate attraverso aggiornamenti di questo manuale. Non si può comunque realizzare un lavoro
completamente soddisfacente se non si dispone degli impianti e delle attrezzature necessarie, ed è per
questo che vi invitiamo a consultare le pagine di questo manuale riguardanti l'attrezzatura specifica e il
catalogo degli attrezzi specifici.

N.B. Provides key information to make the procedure easier to understand and carry out.

CAUTION Refers to specific procedures to carry out for preventing damages to the vehicle.

WARNING Refers to specific procedures to carry out to prevent injuries to the repairer.

Personal safety Failure to completely observe these instructions will result in serious risk of personal

injury.

Safeguarding the environment Sections marked with this symbol indicate the correct use of the vehicle
to prevent damaging the environment.

Vehicle intactness The incomplete or non-observance of these regulations leads to the risk of serious
damage to the vehicle and sometimes even the invalidity of the guarantee.

INDEX OF TOPICS

CHARACTERISTICS CHAR

TOOLING TOOL

MAINTENANCE MAIN

TROUBLESHOOTING TROUBL

ELECTRICAL SYSTEM ELE SYS

ENGINE FROM VEHICLE ENG VE

ENGINE ENG

SUSPENSIONS SUSP

BRAKING SYSTEM BRAK SYS

CHASSIS CHAS

PRE-DELIVERY PRE DE

TIME TIME

INDEX OF TOPICS

CHARACTERISTICS CHAR

Rules

Safety rules

- If work can only be done on the vehicle with the engine running, make sure that the premises are well­ventilated, using special extractors if necessary; never let the engine run in an enclosed area. Exhaust
fumes are toxic.

- The battery electrolyte contains sulphuric acid. Protect your eyes, clothes and skin. Sulphuric acid is
highly corrosive; in the event of contact with your eyes or skin, rinse thoroughly with abundant water
and seek immediate medical attention.

- The battery produces hydrogen, a gas that can be highly explosive. Do not smoke and avoid sparks
or flames near the battery, especially when charging it.

- Fuel is highly flammable and it can be explosive given some conditions. Do not smoke in the working
area, and avoid naked flames or sparks.

- Clean the brake pads in a well-ventilated area, directing the jet of compressed air in such a way that
you do not breathe in the dust produced by the wear of the friction material. Even though the latter
contains no asbestos, inhaling dust is harmful.

Maintenance rules

- Use original PIAGGIO spare parts and lubricants recommended by the Manufacturer. Non-original or
non-conforming spare parts may damage the vehicle.

- Use only the appropriate tools designed for this vehicle.

- Always use new gaskets, sealing rings and split pins upon refitting.

- After removal, clean the components using non-flammable or low flash-point solvents. Lubricate all
the work surfaces, except tapered couplings, before refitting these parts.

- After refitting, make sure that all the components have been installed correctly and work properly.

- For removal, overhaul and refit operations use only tools with metric measures. Metric bolts, nuts and
screws are not interchangeable with coupling members with English measurement. Using unsuitable
coupling members and tools may damage the scooter.

- When carrying out maintenance operations on the vehicle that involve the electrical system, make
sure the electric connections have been made properly, particularly the ground and battery connections.

Vespa S 50 4T 4V (2008) Characteristics

CHAR - 7

Vehicle identification

VEHICLE IDENTIFICATION

Specification Desc./Quantity

Chassis prefix ZAPC383000001001

Engine prefix C383M

Dimensions and mass

WEIGHTS AND DIMENSIONS

Specification

Desc./Quantity

Width 740 mm

Length 1755 mm

Wheelbase 1290 mm

Maximum height 1140 mm

Kerb weight 110 ± 5 kg

Engine

ENGINE

Specification

Desc./Quantity

Type single-cylinder, four-stroke and four-valve, air-cooled engine

Characteristics Vespa S 50 4T 4V (2008)

CHAR - 8

Specification Desc./Quantity

Bore 39 mm

Stroke 41.8 mm

Cubic capacity 49.93 cm³

Max. Power 3.2 kW at 8250 rpm

MAX. torque 3.8 Nm at 7750 rpm

Compression ratio 11.5 ÷ 12 : 1

Timing system single overhead camshaft, chain-driven, on the left-hand side,

three-arm rocking levers set up with threaded set screw

Engine idle speed 1900 ÷ 2000 rpm

Air filter Sponge, soaked in a mixture (50% SELENIA Air Filter Oil and

50% unleaded petrol).

Starting system electric starter/kick-starter

Lubrication engine lubrication with lobe pump (in the crankcase) driven by

a chain. Mesh pre-filter and centrifugal on the crankshaft

Fuel supply Gravity feed, with unleaded petrol (with a minimum octane rat-

ing of 95) with carburettor.

Valve clearance (cold engine) intake 0.10 mm

discharge 0.15 mm

Carburettor depression type, KEIHIN NCV ø 20

Cooling forced air circulation

OIL PUMP

Specification Desc./Quantity

Type Trochoidal

Distance between the rotors Admissible limit clearance: 0.15 mm

Axial rotor clearance Limit values admitted: 0.09 mm

Distance between the outer rotor and the pump body Admissible limit clearance: 0.20 mm

Levelness 0.1 mm

OIL FILTER

Specification

Desc./Quantity

Type mesh, plastic and centrifugal filter, before the oil pump and co-

axially mounted onto the crankshaft keyed on the right crank

Transmission

TRANSMISSION

Specification

Desc./Quantity

Transmission With automatic expandable pulley variator, torque server, V-

belt, automatic clutch, gear reduction unit.

Capacities

CAPACITY

Specification

Desc./Quantity

Fuel tank (including a ~ 2 l reserve) approx. 8.5 l

Rear hub 85 cm³

Engine oil ~ 850 cc

Electrical system

When the advance check is carried out with a stroboscopic gun, add 10° flywheel keying to the table
below.

Vespa S 50 4T 4V (2008) Characteristics

CHAR - 9

ELECTRICAL COMPONENTS

Specification Desc./Quantity

1 Ignition advance reference in table
2 Spark plug NGK ER9EH-N
3 Battery 12V - 9Ah
4 Fuses One 15A fuse - Two 7.5A fuses
5 Generator single-phase alternating current

CHECKING REMOTE CONTROLS «A» OPER­ATING AS CIRCUIT BREAKERS

1) Check that, given regular conditions, there is no
continuity between terminals 30 and 87.

2) Apply 12V voltage to power terminals 85 and 86
of the remote control.

3) With the remote control powered, check that
there is continuity between terminals 30 and 87.

4) If these conditions are not fulfilled, the remote
control is damaged and must be replaced.

TURN INDICATOR SWITCH

Characteristics Vespa S 50 4T 4V (2008)

CHAR - 10

KEY SWITCH

LIGHT SWITCH

STARTER BUTTON

HORN BUTTON

Vespa S 50 4T 4V (2008) Characteristics

CHAR - 11

STOP BUTTON

Resistance between green cable and ground con­nection: approx. 170 Ohm

- Primary resistance: 0.5 ÷ 0.6 Ohm

- Resistance between primary and ground con­nection: infinite

- Resistance between primary and HV output: 3 ÷

3.6 kOhm

- Shielded cap: 5000 Ohm

- Power: 120 W

- resistance between BLUE cable and GROUND
CONNECTION: 1 Ohm

Frame and suspensions

CHASSIS AND SUSPENSIONS

Specification

Desc./Quantity

Type Unitised body made of stamped plate

Characteristics Vespa S 50 4T 4V (2008)

CHAR - 12

Specification Desc./Quantity

Front suspension Single arm suspension with swinging arm articulated to the

steering tube. Hydraulic double-acting shock absorber and co-

axial spring

Front suspension stroke 70 mm

Trail (suspension rebounded/compressed) 71/68 mm

Rear suspension Single hydraulic double-acting shock absorber, helical coaxial

spring. Chassis to engine support with swinging arm.

Rear suspension travel: 83.5 mm

Brakes

BRAKES

Specification Desc./Quantity

Front Disc brake, Ø 200 mm
Rear Drum brake, Ø 110 mm

Wheels and tyres

WHEELS AND TYRES

Specification Desc./Quantity

Front tyre size 110/70"-11"

Rear tyre size 120/70-10"

Front tyre pressure 1.6 bar

Rear tyre pressure: 2 bar

Light alloy rims (Front rim) 2.50" x 11"

Light alloy rims (rear rim) 3.00 x 10"

N.B.

CHECK AND ADJUST TYRE PRESSURE WITH TYRES AT AMBIENT TEMPERATURE. ADJUST
PRESSURE ACCORDING TO THE WEIGHT OF RIDER AND ACCESSORIES.

Tightening Torques

STEERING ASSEMBLY

Name

Torque in Nm

Upper steering ring nut 30 ÷ 40
Steering lower ring nut 8 ÷ 10

Handlebar locking 50 ÷ 55 Nm

FRAME ASSEMBLY

Name

Torque in Nm

Engine-swinging arm bolt 33 ÷ 41
Frame-swinging arm bolt 44 ÷ 52

Shock absorber - chassis nut 20 ÷ 25

Shock absorber nut-engine 33 ÷ 41

Rear wheel nut 104 ÷ 126

Screws fixing the odometer reel plate 4 ÷ 6

FRONT SUSPENSION

Name

Torque in Nm

Shock absorber upper nut 20 ÷ 30

Front wheel axle nut 75 ÷ 90

Shock absorber upper bracket bolts 20 ÷ 25

Wheel rim screws 20 ÷ 25

Shock absorber lower bolts (°) 20 ÷ 27

(°) Lock these two bolts once the central upper nut of the shock absorber has been tightened.

Vespa S 50 4T 4V (2008) Characteristics

CHAR - 13

N.B.

FOR SAFETY LOCKS, SEE THE «PRE-DELIVERY» CHAPTER.

FRONT BRAKE

Name Torque in Nm

Brake fluid pump-hose fitting 8 ÷ 12

Brake fluid pipe-calliper fitting 20 ÷ 25

Screw tightening calliper to the support 20 ÷ 25

Brake disc screw 5 ÷ 6.5

Oil bleed valve (on the calliper) 10 ÷ 12

Handlebar pump 7 ÷ 10

ENGINE ASSEMBLY

Name Torque in Nm

Ignition spark plug: 10 ÷ 15 Nm

Floating head cover screws 6 ÷ 7

Head-cylinder stud bolt nuts 6 ÷ 7 + 90° + 90° *

Screws fixing head and cylinder to crankcase 8 ÷ 10

Chain tensioner pad screw 5 ÷ 7 Nm

Timing chain tensioner central screw 5 - 6

Camshaft pulley screw 12 ÷ 14

Rocking lever axle and camshaft bearing screw 3 ÷ 4 Nm

Rocking levers adjusting nuts: 7 ÷ 9 Nm

Engine oil pre-filter cover: 25 ÷ 28 Nm

Engine oil drainage cap 25 ÷ 28

Flywheel nut 40 to 44 N.m

Stator screws 3 ÷ 4

Pick-up screws 3 ÷ 4

Oil pump bulkhead screw 4 ÷ 5

Timing chain/oil pump compartment cover screws 4 ÷ 5

Oil decantation labyrinth sheet screws 7 ÷ 8

Oil pump crown screw 8 ÷ 10

Screws fixing oil pump to the crankcase 5 ÷ 6

Oil sump screws 8 ÷ 10 Nm

Inlet manifold screw 7 ÷ 9

Carburettor/manifold clamp screw 1.2 ÷ 1.5

Screws fixing cables to starter motor 1.5 ÷ 2.5

Starter screws 11 ÷ 13

Transmission cover screws 11 ÷ 13

Start-up lever screw 11 ÷ 13

Crankcase cooling cover screw 2 ÷ 2.5

Clutch assembly nut 55 ÷ 60

Crankshaft pulley nut 18 to 20 + 90° Nm
Driven pulley shaft nut 40 to 44 Nm
Hub oil drainage screw 3 ÷ 5 Nm

Rear hub cap screws 11 ÷ 13

Crankcase half union screw 8 ÷ 10

* When assembling the new stud bolts, nut tightening involves 3 turns of 90° each after the first locking
at 6 ÷ 7 Nm, consequently: 6 ÷ 7 Nm + 90° + 90° + 90° at criss-crossed sequences.

Overhaul data

Assembly clearances

Characteristics Vespa S 50 4T 4V (2008)

CHAR - 14

Cylinder - piston assy.

COUPLING BETWEEN PISTON AND CYLINDER

Name

Initials Cylinder Piston Play on fitting

Cylinder A 38.993 ÷ 39.000 38.954 ÷ 38.961 0.032 ÷ 0.046
Cylinder B 39.000 ÷ 39.007 38.961 ÷ 38.968 0.032 ÷ 0.046

Piston C 39.007 ÷ 39.014 38.968 ÷ 38.975 0.032 ÷ 0.046

Piston D 39.014 ÷ 39.021 38.975 ÷ 38.982 0.032 ÷ 0.046
Cylinder 1st oversize A1 39.193 ÷ 39.200 39.154 ÷ 39.161 0.032 ÷ 0.046
Cylinder 1st oversize B1 39.200 ÷ 39.207 39.161 ÷ 39.168 0.032 ÷ 0.046

Piston 1st oversize C1 39.207 ÷ 39.214 39.168 ÷ 39.175 0.032 ÷ 0.046

Piston 1st oversize D1 39.214 ÷ 39.221 39.175 ÷ 39.182 0.032 ÷ 0.046
Cylinder 2nd oversize A2 39.393 ÷ 39.400 39.354 ÷ 39.361 0.032 ÷ 0.046
Cylinder 2nd oversize B2 39.400 ÷ 39.407 39.361 ÷ 39.368 0.032 ÷ 0.046

Piston 2nd oversize C2 39.407 ÷ 39.414 39.368 ÷ 39.375 0.032 ÷ 0.046

Piston 2nd oversize D2 39.414 ÷ 39.421 39.375 ÷ 39.382 0.032 ÷ 0.046
Cylinder 3rd oversize A3 39.593 ÷ 39.600 39.554 ÷ 39.561 0.032 ÷ 0.046
Cylinder 3rd oversize B3 39.600 ÷ 39.607 39.561 ÷ 39.568 0.032 ÷ 0.046

Piston 3rd oversize C3 39.607 ÷ 39.614 39.568 ÷ 39.575 0.032 ÷ 0.046
Piston 3rd oversize D3 39.614 ÷ 39.621 39.575 ÷ 39.582 0.032 ÷ 0.046

N.B.

THE PISTON MUST BE INSTALLED WITH THE ARROW FACING TOWARDS THE EXHAUST SIDE,
THE PISTON RINGS MUST BE INSTALLED WITH THE WORD «TOP» OR THE STAMPED MARK
FACING UPWARDS.

- Measure the outside diameter of the gudgeon
pin.

Characteristic

Pin outside diameter

13 +0 -0.004 mm

Minimum admissible diameter gudgeon pin

12.990 mm

Vespa S 50 4T 4V (2008) Characteristics

CHAR - 15

- Measure the diameter of the bearings on the pis­ton.

Characteristic

Pin seat diameter

13 +0.005 +0.010 mm

- Calculate the piston pin coupling clearance.

N.B.

THE PIN HOUSINGS HAVE 2 LUBRICATION CHANNELS. FOR THIS REASON, MEASUREMENT
MUST BE MADE ACCORDING TO THE PISTON AXIS.

Characteristic

Standard clearance

0.005 ÷ 0.014 mm

- Carefully clean the seal housings.

- Measure the coupling clearance between the
sealing rings and the grooves using suitable sen­sors, as shown in the diagram.

- If the clearance is greater than that indicated in
the table, replace the piston.

N.B.
MEASURE THE CLEARANCE BY INSERTING THE BLADE

OF THE FEELER THICKNESS GAUGE FROM THE SECOND
SEAL SIDE.

Fitting clearance

Top piston ring - standard coupling clearance

0.03 ÷ 0.065 mm Top piston ring - maximum clear-

ance allowed after use 0.07 mm Middle piston
ring - standard coupling clearance 0.02 ÷ 0.055

mm Middle piston ring - maximum clearance al-

lowed after use 0.06 mm oil scraper ring - stand­ard coupling clearance 0.04 ÷ 0.16 mm oil scraper
ring - maximum clearance allowed after use

0.17 mm

- Using a bore meter, measure the inner cylinder
diameter at three different points according to the
directions shown in the figure.

- Check that the coupling surface with the head is
not worn or misshapen.

Characteristics Vespa S 50 4T 4V (2008)

CHAR - 16

- Pistons and cylinders are classified into catego­ries based on their diameter. The coupling is car­ried out in pairs (A-A, B-B, C-C, D-D).

Characteristic

Maximum allowable run-out:

0.05 mm

Piston rings

- Alternately insert the three sealing rings into the
cylinder, in the area where it retains its original di­ameter. Using the piston, insert the rings perpen­dicularly to the cylinder axis.

- Measure the opening, see figure, of the sealing
rings using a thickness gauge.

- If any measurements are greater than specified,
replace the piston rings.

N.B.
BEFORE REPLACING ONLY THE PISTON RINGS, ENSURE

THAT THE CLEARANCE BETWEEN THE PISTON RINGS
AND THE PISTON RING GROOVES, AND BETWEEN THE
PISTON AND THE CYLINDER, IS AS SPECIFIED. IN ANY
CASE, NEW PISTON RINGS USED IN COMBINATION WITH
A USED CYLINDER MAY HAVE DIFFERENT BEDDING
CONDITIONS THAN THE STANDARD.

SEAL RINGS

Name

Description Dimensions Initials Quantity

1st Compression ring 39 x 1 A 0.08 ÷ 0.20

Vespa S 50 4T 4V (2008) Characteristics

CHAR - 17

Name Description Dimensions Initials Quantity

2nd Compression ring 39 x 1 A 0.05 ÷ 0.20

Oil scraper ring 39 x 2 A 0.20 ÷ 0.70

1st Compression ring

1st Oversize

39.2 x 1 A 0.08 ÷ 0.20

2nd Compression ring

1st Oversize

39.2 x 1 A 0.05 ÷ 0.20

Oil scraper ring 1st

Oversize

39.2 x 2 A 0.20 ÷ 0.70

1st Compression ring

2nd Oversize

39.4 x 1 A 0.08 ÷ 0.20

2nd Compression ring

2nd Oversize

39.4 x 1 A 0.05 ÷ 0.20

Oil scraper ring 2nd

Oversize

39.4 x 2 A 0.20 ÷ 0.70

1st Compression ring

3rd Oversize

39.6 x 1 A 0.08 ÷ 0.20

2nd Compression ring

3rd Oversize

39.6 x 1 A 0.05 ÷ 0.20

Oil scraper ring 3rd

Oversize

39.6 x 2 A 0.20 ÷ 0.70

Crankcase - crankshaft - connecting rod

AXIAL CLEARANCE BETWEEN CRANKSHAFT AND CRANKCASE

Name

Description Dimensions Initials Quantity

Half-shaft, transmission

side

14 +0 -0.005 A

Flywheel-side half-shaft 16 +0 -0.005 B

Connecting rod 14.8 +0.05 -0 C

Spacer tool 45.00 / Fits and clearan-

ces D = 0.15 ÷ 0.30

E

Characteristic

Clearance between crankshaft and connecting rod
A = 0.15 ÷ 0.30 mm

Characteristics Vespa S 50 4T 4V (2008)

CHAR - 18

Measure the bearings along X and Y axes

Characteristic

Crankshaft bearing, transmission side

20 -0.012 -0.025 mm

Crankshaft bearing, flywheel side

17 +0.007 0 mm

- Check that the driving shaft cone, the tab seat, the oil seal capacity, the toothed gear and the threaded
tangs are in good working order.

- In case of failures, replace the crankshaft.

Specific tooling

020074Y Support base for checking crankshaft alignment

Vespa S 50 4T 4V (2008) Characteristics

CHAR - 19

- Install the crankshaft on the support and measure
the displacement at the 4 points shown in the fig­ure.

N.B.
IF VALUES OTHER THAN THOSE ALLOWED ARE DETEC-

TED, TRY STRAIGHTENING THE CRANKSHAFT BY IN­SERTING A WOODEN WEDGE BETWEEN THE HALF
SHAFTS OR BY CLOSING THEM WITH A VICE AS NEE­DED. IF EVEN AFTER THIS OPERATION THE VALUES ARE
NOT THOSE ADMITTED, REPLACE THE CRANKSHAFT.

Characteristic

Off-line maximum admitted - A

0.15 mm

Off-line maximum admitted - B

0.02 mm

Off-line maximum admitted - C

0.02 mm

Off-line maximum admitted - D

0.10 mm

- Using a bore gauge, measure the connecting rod
small end diameter.

N.B.
IF THE CONNECTING ROD SMALL END DIAMETER EX-

CEEDS THE STANDARD DIAMETER, EXHIBITS WEAR OR
OVERHEATING, PROCEED TO REPLACE THE CRANK­SHAFT AS DESCRIBED IN THE CRANKCASE AND
CRANKSHAFT CHAPTER.

Characteristic

Rod small end diameter

13 +0.015 + 0.025 mm

Max. diameter admitted: check the small end

13.030 mm

Calculate the coupling clearance between pin and rod small end

Characteristic

Pin - connecting rod clearance

0.015 ÷ 0.029 mm

Cylinder Head

Before performing head service operations, thoroughly clean all coupling surfaces. Note the position of
the springs and the valves so as not to change the original position during refitting

Characteristics Vespa S 50 4T 4V (2008)

CHAR - 20

- Using a trued bar check that the cylinder head
surface is not worn or distorted.

- Check that the camshaft and rocking lever pin
bearings show no signs of wear.

- Check that the cylinder head cover surface, the
intake manifold and the exhaust manifold are not
worn.

- It is advisable to replace the head if any failure is
found.

Characteristic

Maximum allowable run-out:

0.1 mm

- Insert the valves into the cylinder head.

- Alternatively check the intake and exhaust
valves.

- The test is carried out by filling the manifold with
petrol and checking that the head does not ooze
through the valves when these are just pressed
with the fingers.

Measure the camshaft bearing seats and rocking
lever support pins with a bore meter

HEAD CHECK

Specification

Desc./Quantity

Standard diameter (mm) A Ø 32.015 ÷ 32.025 mm
Standard diameter (mm) B Ø 16.0 ÷ 16.018
Standard diameter (mm) C Ø 11.0 ÷ 11.018

Vespa S 50 4T 4V (2008) Characteristics

CHAR - 21

Measure the unloaded spring length.

•

Standard length: 31.3 mm

•

Admissible limit after use: 29.3

- Clean the valve seats of any carbon residues.

- Using the Prussian blue, check the width of the
impression on the valve seat "V".

Characteristic

Standard value:

1 - 1.3 mm

Admissible limit:

1.6 mm

- If the impression width on the valve seat is larger than the prescribed limits, true the seats with a 45°
mill and then grind.

- In case of excessive wear or damages, replace the head.

STANDARD VALVE LENGTH

Specification

Desc./Quantity

Inlet: standard length 74.9 mm

Outlet: standard length 74.35 mm

Characteristics Vespa S 50 4T 4V (2008)

CHAR - 22

- Measure the diameter of the valve stems in the
three positions indicated in the diagram.

STANDARD DIAMETER

Specification Desc./Quantity

Inlet 3.970 ÷ 3.985 mm

drainage 3.960 ÷ 3.975 mm

MINIMUM DIAMETER PERMITTED

Specification Desc./Quantity

Inlet 3.958 mm

drainage 3.945 mm

- Calculate the clearance between valve and valve guide.

- Check the concentricity of the valve head by ar­ranging a dial gauge at right angle relative to the
valve head and rotate it on a "V" shaped abutment.

Characteristic

Admissible limit:

0.03 mm

- Check the deviation of the valve stem by resting
it on a «V» shaped abutment and measuring the
extent of the deformation with a dial gauge.

Characteristic

Limit values admitted:

0.1 mm

Vespa S 50 4T 4V (2008) Characteristics

CHAR - 23

Measure the valve guides

VALVE GUIDE DIAMETER

Specification Desc./Quantity

Valve guide Standard diameter: 4 + 0.012 mm
Valve guide Maximum admissible diameter: 4 + 0.022 mm

- After measuring the valve guide diameter and the
valve stem diameter, check clearance between
guide and stem.

INLET

Specification

Desc./Quantity

Standard clearance 0.015 ÷ 0.042 mm

Admissible limit 0.06 mm

OUTLET

Specification

Desc./Quantity

Standard clearance 0.025 ÷ 0.052 mm

Admissible limit 0.07 mm

- If no anomalies are found during the above checks, you can use the same valves. To obtain better
sealing performance, grind the valve seats. Grind the valves gently with a fine-grained lapping com­pound. During the grinding, keep the cylinder head with the valve axes in a horizontal position. This will
prevent the lapping compound residues from penetrating between the valve stem and the guide (see
figure).

CAUTION

TO AVOID SCORING THE FAYING SURFACE, DO NOT KEEP ROTATING THE VALVE WHEN NO
LAPPING COMPOUND IS LEFT. CAREFULLY WASH THE CYLINDER HEAD AND THE VALVES
WITH A SUITABLE PRODUCT FOR THE TYPE OF LAPPING COMPOUND BEING USED.

CAUTION

DO NOT REVERSE THE FITTING POSITIONS OF THE VALVES (RIGHT - LEFT).

Characteristics Vespa S 50 4T 4V (2008)

CHAR - 24

- Inspect the cam shaft for signs of abnormal wear
on the cams.

Characteristic

Standard diameter - Bearing A:

Ø 12 +0.002 +0.010

mm Standard diameter - Bearing B:

Ø 16-0.015 -0.023 mm

Minimum diameter allowed - Bearing A:

Ø 11.98 mm

Minimum diameter allowed - Bearing B:

Ø 15.96 mm

-Using a gauge, measure the cam height.
Check the axial clearance of the camshaft

- If any of the above dimensions are outside the
specified limits, or there are signs of excessive
wear, replace the defective components with new
ones.

N.B.
A BALL BEARING IS FITTED ON BEARING «A»; CONSE-

QUENTLY, BEARING «B» IS THE MOST IMPORTANT AS IT
WORKS DIRECTLY ON THE HEAD ALUMINIUM

Characteristic

Standard height - Inlet

24.397 mm

Standard height - Outlet

23.996 mm

Fitting clearance

Maximum admissible axial clearance: 0.5 mm

- Measure the outside diameter of the rocking lever pins

- Check the rocker pins do not show signs of wear or scoring.

- Measure the internal diameter of each rocking lever.

- Check that the pad in contact with the cam is not worn.

ROCKING LEVERS AND PIN DIAMETER:

Specification

Desc./Quantity

Rocking levers - Inside diameter 11.015 ÷ 11.035 mm

Rocking levers - Pins diameter 10.977 ÷ 10.985 mm

Vespa S 50 4T 4V (2008) Characteristics

CHAR - 25

Slot packing system

Characteristic

Compression ratio

11.5 ÷ 12 : 1

PISTON PROTRUSION CHECK

Name

Measure A Thickness

shimming_1 1.7 ÷ 1.95 0.25
shimming_2 1.95 ÷ 2.2 0.35

Products

RECOMMENDED PRODUCTS TABLE

Product

Description Specifications

AGIP ROTRA 80W-90 Rear hub oil SAE 80W/90 Oil that exceeds the re-

quirements of API GL3 specifications

AGIP CITY HI TEC 4T Oil to lubricate flexible transmissions

(brakes, throttle control and odometer)

Oil for 4-stroke engines

AGIP FILTER OIL Oil for air filter sponge Mineral oil with specific additives for in-

creased adhesiveness

AGIP CITY HI TEC 4T Engine oil SAE 5W-40, API SL, ACEA A3, JASO MA

Synthetic oil

AGIP GREASE MU3 Grease for odometer transmission gear

case

Soap-based lithium grease with NLGI 3;

ISO-L-XBCHA3, DIN K3K-20

AGIP BRAKE 4 Brake fluid FMVSS DOT 4 Synthetic fluid

MONTBLANC MOLYBDENUM

GREASE

Grease for driven pulley shaft adjusting
ring and movable driven pulley housing

Grease with Molybdenum disulphide

AGIP GREASE PV2 Grease for steering bearings, bolt seat-

ings for swinging arms and faying surface

of driven pulley spring (only pulley side)

Soap-based lithium and zinc oxide

grease containing NLGI 2; ISO-L-

XBCIB2

AGIP GP 330 Grease for brake levers, throttle White calcium complex soap-based

spray grease with NLGI 2; ISO-L-XBCIB2

Characteristics Vespa S 50 4T 4V (2008)

CHAR - 26

INDEX OF TOPICS

TOOLING TOOL

TOOLS

Stores code Description

001467Y008 Pliers to extract 17 mm ø bearings

001467Y029 Bell for bearings, O.D. 38 mm

004499Y Bearing extractor. Fitted with: 1 Bell, 2

Sleeve, 3 Screw, 6 Ring, 27 Half rings, 34

Half rings

005095Y Engine support

008119Y009 Tube to assemble shafts and axles

020004Y Punch for removing fifth wheels from

headstock

Tooling Vespa S 50 4T 4V (2008)

TOOL - 28

Stores code Description

020055Y Wrench for steering tube ring nut

020074Y Tool to align crankshaft
020150Y Air heater support

020151Y Air heater

020162Y Flywheel extractor

020171Y Punch for driven pulley roller bearing

020265Y Bearing fitting base

Vespa S 50 4T 4V (2008) Tooling

TOOL - 29

Stores code Description

020288Y Fork to assemble piston on cylinder

020291Y Valve fitting/ removal tool

020306Y Punch for assembling valve seal rings

020329Y MityVac vacuum-operated pump

020330Y Stroboscopic light to check timing

020331Y Digital multimeter

Tooling Vespa S 50 4T 4V (2008)

TOOL - 30

Stores code Description

020332Y Digital rpm indicator

020334Y Multiple battery charger

020335Y Magnetic support for dial gauge

020340Y Flywheel and transmission oil seals fitting

punch

020358Y 37x40-mm Adaptor
020359Y 42x47-mm Adaptor

Vespa S 50 4T 4V (2008) Tooling

TOOL - 31

Stores code Description

020360Y 52x55-mm Adaptor

020362Y 12 mm guide

020363Y 20-mm guide

020364Y 25-mm guide

020376Y Adaptor handle

020431Y Valve oil seal extractor

Tooling Vespa S 50 4T 4V (2008)

TOOL - 32

Stores code Description

020432Y Tool to fit the start-up sector spring

020439Y 17 mm guide

020444Y Pin fitting/removal tool
020448Y Pin lock fitting tool

020449Y Piston position check support

020450Y Camshaft fitting/removal tool

020451Y Driving pulley lock wrench
020452Y Tube for removing and refitting the driven

pulley shaft

Vespa S 50 4T 4V (2008) Tooling

TOOL - 33

Stores code Description

020456Y Ø 24 mm adaptor

020565Y Flywheel lock calliper spanner

020683Y Valve pressing member

Tooling Vespa S 50 4T 4V (2008)

TOOL - 34

INDEX OF TOPICS

MAINTENANCE MAIN

Maintenance chart

SCHEDULED MAINTENANCE TABLE

I: CHECK AND CLEAN, ADJUST, LUBRICATE OR REPLACE IF NECESSARY.
C: CLEAN, R: REPLACE, A: ADJUST, L: LUBRICATE

* Replace every 2 years

Km x 1000 1 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60

Safety locks I I I I I I
Spark plug R R R R R R R R R R
Driving belt I R I R I R I R I R
Throttle control A A A A A A
Tyre condition and
wear

I I I I I

Air filter C C C C C
Oil filter (mesh) C C C C C C C C C C
Solenoid filter C C C C C C C C C C
Valve clearance I I I I I I
Electrical system
and battery

I I I I I I I I I I I

Cylinder ventila­tion system

I I

Brake control lev­ers

L L L L L L

Brake oil level (*) I I I I I I I I I I I
Hub oil level R I R I R I R I R I R
Engine oil R I R I R I R I R I R I R I R I R I R I R
Brake Pads/Shoes I I I I I I I I I I I
Tyre pressure I I I I I I I I I I I
Headlight A A A A A
Vehicle test drive I I I I I I I I I I I
Idle speed A A A A A A
Odometer gear L L L L L
Variable speed
rollers

I R I R I R I R I R

Suspensions I I I I I
Steering A A A A A A
Transmissions L L L L L

Carburettor

The carburettor features a solenoid valve "A" that,
via an ECU, manages an extra flow of air.
It is connected to the carburettor via flexible pipes
as shown in the figure.
The valve is placed under the helmet compartment
as shown in the picture.
Pipe "B" is coupled to a filter placed inside the
body. The solenoid filter should be cleaned ac­cording to the kilometres travelled as instructed in
the scheduled maintenance chart.

Maintenance Vespa S 50 4T 4V (2008)

MAIN - 36

- Disassemble the carburettor in its parts, wash all
of them with solvent, dry all body grooves with
compressed air to ensure adequate cleaning.

- Check carefully that the parts are in good condi­tion.

-The throttle valve should move freely in the
chamber. Replace valve in case of wear due to
excessive clearance.

- If there are wear marks in the chamber causing
inadequate tightness or a free valve slide (even if
it is new), replace the carburettor.

- It is advisable to replace the gaskets at every refit.

WARNING
PETROL IS HIGHLY EXPLOSIVE ALWAYS REPLACE THE

GASKETS TO AVOID PETROL LEAKS

1. Needle valve - 2. Idle speed adjustment screw - 3. Max jet - 4. Accelerating pump - 5. Tapered pin -

6. Jet holder - 7. Float - 8. Chamber - 9. Starter device - 10. Vacuum valve - 11. Cover - 12. Minimum

jet.

Vespa S 50 4T 4V (2008) Maintenance

MAIN - 37

Checking the spark advance

The vehicle is fitted with a variable advance elec­tronic device. There are two timing references on
the flywheel cover in order to ensure a better pre­cision when detecting the reference on the fan.

CAUTION
SHOULD THE FLASH INDICATIONS BE UNSTABLE AND

THE RPM INDICATION DOES NOT CORRESPOND WITH
THE TRUE ENGINE SPEED VARIATION (FOR EXAMPLE,
VALUES SHOWN ARE HALVED), INSTALL A 10 ÷ 15 KΩ
RESISTIVE CABLE CONNECTED IN SERIES TO AN HV CA­BLE. IF THE IRREGULAR READING CONTINUES AFTER
THIS OPERATION, CHECK THE COMPONENTS OF THE
IGNITION SYSTEM.

When the advance check is carried out with a stroboscopic gun, add 10° flywheel keying to the table
below.

Spark plug

Disconnect and remove the spark plug tube.

- Examine it carefully and replace it if the insulator
is chipped or cracked.

- Measure electrode gap with a thickness gauge
and, if necessary, adjust the gap by carefully bend­ing the outer electrode forward or away.

- Make sure the sealing washer is in good condi­tions.

Maintenance Vespa S 50 4T 4V (2008)

MAIN - 38

- Fit the spark plug, screw it manually and lock it
to the prescribed torque with a spark plug spanner.

Electric characteristic

Candela

NGK ER9EH-6N

Distanza elettrodi:

0,6 mm

Locking torques (N*m)

Candela 8 ÷ 10

Hub oil

Check

Rest the vehicle on its centre stand on an even
surface.

- Unscrew the oil dipstick "A", dry it with a clean
cloth and reinsert it, screwing it in thoroughly.

- Pull out the dipstick and check that the oil level is
above the "middle" notch (dipstick with 3 notches).
For dipsticks with 2 notches, the oil level must re­main in the lower half of the dipstick.

-Screw up the oil dipstick again and make sure it
is locked properly into place.

Recommended products

AGIP ROTRA 80W-90 rear hub oil

SAE 80W/90 Oil that exceeds the requirements of
API GL3 specifications

Vespa S 50 4T 4V (2008) Maintenance

MAIN - 39

Replacement

Remove the oil filler cap/dipstick "A".

- Unscrew the oil drainage plug "B" shown in the
figure and drain out all the oil.

- Screw the drainage plug back and fill up the hub
with the required oil (about 100 cm³)

Air filter

Once the lower section of the left side cover has
been removed, take out the air cleaner cap by un­screwing the 4 fixing screws and the 2 knobs (they
can be reached by tipping the saddle and remov­ing the helmet compartment); afterwards, remove
the filtering element.
Cleaning:

- Wash with water and car shampoo;

- Dry with a clean cloth and short blasts of com­pressed air; do not wring;

- Immerse it in a mixture of 50% oil and 50 % petrol.

- Allow the filtering element to drip dry and then
press it in your hands but without squeezing.

CAUTION
NEVER RUN THE ENGINE WITHOUT THE AIR FILTER,

THIS WOULD RESULT IN AN EXCESSIVE WEAR OF THE
PISTON AND CYLINDER.

Engine oil

Maintenance Vespa S 50 4T 4V (2008)

MAIN - 40

Replacement

Loosen the oil filler plug.

- Unscrew the drainage plug from the mesh filter
on the flywheel side, and let the oil drain off.

- Tighten the drainage plug and refill with ~
600-650 cm³ of oil.

Check

Park the vehicle on a level surface and rest it on
its stand (cold engine).

- Check that the oil level is between the MAX and
MIN marks on the dipstick.

- The MAX level reference indicates ~ 850 cm³ in
the engine.

- If the oil level is close to the MIN mark, top-up by
adding oil but do not exceed the MAX level.

Recommended products

AGIP CITY HI TEC 4T Oil to lubricate flexible
transmissions (brakes, throttle control and od­ometer)

Oil for 4-stroke engines

Engine oil filter

- Change oil when the engine is hot.

- Place a container under the oil sump and remove
the oil drainage cap.

- After draining the oil, clean the mesh filter with a
specific solvent and then blow it with compressed
air.

- The filter can be reached after removing cap
"A" (see figure).

Vespa S 50 4T 4V (2008) Maintenance

MAIN - 41

- After this operation, refit the filter and screw the
oil cap at the prescribed torque using a new O­Ring

- Refill the engine with oil through the oil filling hole
located in the oil sump.

- Engine oil capacity: ~ 850 cc.

- Lock the cap manually.

N.B.

Run the engine for a couple of minutes and check the oil level
when the engine is cold. The level should always be below the
MAX mark

N.B.

For the first top-up or when servicing, add 850 cm³ of engine
oil; for any other case, add 650 cm³ and top-up, if required.

Recommended products

AGIP CITY HI TEC 4T Engine oil

SAE 5W-40 Synthetic oil that exceed the require­ments of API SL, ACEA A3, JASO MA specifica­tions

Locking torques (N*m)

Engine oil pre-filter cover 25 ÷ 28 Nm

Checking the ignition timing

- Turn the flywheel clockwise until its 2nd notch
coincides with the Pick-up reference mark as
shown in the figure.
Make sure that the reference point on the camshaft
command crown is aligned with the reference point
on the head as shown in the second figure.
If the reference is opposite the indicator on the
head, turn the crankshaft once more as the piston
must be at the TDC of the bursting phase.

N.B.
TIME THE TIMING SYSTEM UNIT AS DESCRIBED IN CHAP-

TER 6 IF IT IS NOT IN PHASE

Maintenance Vespa S 50 4T 4V (2008)

MAIN - 42

Checking the valve clearance

- Remove the spark plug access cover, undo the
4 fixing screws indicated in the figure and remove
the tappet cover.

- To check valve clearance, centre the reference
marks of the timing system point as described
above.

- Use a thickness gauge to check valve clearance

- If the valve clearance values, inlet and outlet re­spectively, differ from those indicated below, re­place the calibrated pads in order to restore the
correct valve clearance.

Characteristic

Inlet (with cold engine)

0.10 mm

Outlet (with cold engine)

0.15 mm

Headlight adjustment

Proceed as follows:

1. Place the vehicle, in running order and with the
tyres inflated to the prescribed pressure, on a flat
surface 10-m away from a white screen situated in
a shaded area, making sure that the longitudinal
axis of the scooter is perpendicular to the screen;

2. Turn on the headlight and check that the bor­derline of the projected light beam on the screen
is not lower than 9/10 of the distance from the
ground to the centre of vehicle headlamp and high­er than 7/10;

3. If otherwise, adjust the right headlight with screw
«A».

N.B.
THE ABOVE PROCEDURE COMPLIES WITH THE EURO-

PEAN STANDARDS REGARDING MAXIMUM AND MINI­MUM HEIGHT OF LIGHT BEAMS. REFER TO THE STATU­TORY REGULATIONS IN FORCE IN EVERY COUNTRY
WHERE THE VEHICLE IS USED.

Vespa S 50 4T 4V (2008) Maintenance

MAIN - 43

SAS filters inspection and cleaning

Undo the two screws «A» of the side fairing and
remove the fairing. Undo the three screws «B» and
remove the housing cover of the secondary air
system. Detach the housing cover and remove the
filtering element «C» made of sponge. Wash the
sponge with water and neutral soap, then dry with
a clean cloth and short blasts of compressed air.
While cleaning the filter, check the condition of the
reed valve «D», and fit it back in place on the
housing.
Before closing the cover of the SAS housing,
check the good condition of the sealing O-ring; re­place it if damaged or deformed.

N.B.
The reed valve can be inserted in only one direction on the

SAS housing

Maintenance Vespa S 50 4T 4V (2008)

MAIN - 44

INDEX OF TOPICS

TROUBLESHOOTING TROUBL

Engine

Poor performance

POOR PERFORMANCE

Possible Cause Operation

Air filter obstructed or dirty. Dismantle the sponge, wash with water and shampoo, then

soak it in a mixture of 50% petrol and 50% Selenia Air Filter Oil,

then allow to drip dry. Wring out water manually without

squeezing and reassemble.

Carburettor nozzles clogged or dirty Dismantle, wash with solvent and dry with compressed air

Dirty or faulty vacuum-operated cock Check the filter on the cock, remove the petrol and wash the

tank, if necessary. Replace the cock as a last resource.

Clutch slipping Check the clutch system and/or the bell and replace if neces-

sary

Inefficient automatic transmission Check the rollers and the pulley movement, replace the dam-

aged parts and lubricate the driven pulley moveable guide with

Montblanc Molybdenum Grease

Lack of compression: parts, cylinder and valves worn Replace the worn parts

Oil level exceeds maximum Check for causes and fill to reach the correct level

Excess of encrustations in the combustion chamber Descale the cylinder, the piston, the head and the valves

Incorrect timing or worn timing system elements Time the system again or replace the worn parts (see 50 4T

Engines manual)

Muffler obstructed Replace

Fuel filter on vacuum operated cock blocked Clean the cock filter

Wrong valve adjustment Adjust the valve clearance properly

Valve seat distorted Replace the head assembly

Worn cylinder, Worn or broken piston rings Replace the piston cylinder assembly or just the piston rings

Rear wheel spins at idle

REAR WHEEL

Possible Cause

Operation

Idling rpm too high Check the idling speed and, if necessary, adjust the C.O.

Clutch fault Check the spring/friction mass and the clutch bell

Air filter housing not sealed Correctly refit the filter housing and replace it if it is damaged

Purifier-carburettor fitting damaged Replace

Starting difficulties

START-UP PROBLEMS

Possible Cause

Operation

Defective spark plug or with incorrect electrode gap Check and if necessary replace the spark plug and the elec-

trode gap

Battery flat Check the state of the battery. If it shows signs of sulphation

replace it and bring the new battery into service charging it for

eight hours at a current of 1/10 of the capacity of the battery

itself

- Engine flooded. Start the vehicle keeping the throttle fully open alternately mak­ing the engine run for approx. five seconds and stopping for

other five seconds. If however it does not start, remove the

spark plug, the engine over with the throttle open being careful

to keep the cap in contact with the spark plug and the spark
plug grounded but away from its hole. Refit a dry spark plug

and start the vehicle.

Vacuum operated cock failure Check that fuel is adequately supplied through the pipe by ap-

plying a vacuum to the suction pipe

Troubleshooting Vespa S 50 4T 4V (2008)

TROUBL - 46

Possible Cause Operation

Failing automatic starter on the carburettor Check the electrical wiring and mechanical movement, replace

if necessary.

Wrong ignition advance Check flywheel keying on the crankshaft, replace control unit if

necessary

Incorrect valve sealing or valve adjustment Inspect the head and/or restore the correct clearance

Rpm too low at start-up or engine and start-up system dam-

aged

Check the starter motor and the system.

Altered fuel characteristics Drain off the fuel no longer up to standard; then, refill

Carburettor nozzles clogged or dirty Dismantle, wash with solvent and dry with compressed air

Engine tends to cut-off at full throttle

ENGINE STOP FULL THROTTLE

Possible Cause Operation

Maximum jet clogged Remove the carburettor, wash with solvent and dry with com-

pressed air

Water or condensation in the carburettor chamber Remove the chamber, wash with solvent and dry with com-

pressed air or empty the tank through the appropriate bleed

screw

Incorrect ignition advance Use a stroboscopic light to check ignition advance and the fly-

wheel correct keying

Air filter blocked or dirty. Dismantle the sponge, wash with water and shampoo, then

soak it in a mixture of 50% petrol and 50% of specific oil (Se­lenia Air Filter Oil), then hand dry without squeezing, allow to

drip dry and then reassemble.

Incorrect float level Restore the correct level in the chamber (the float must be par-

allel to the upper cover contact plane, that is the throttle valve

membrane cover)

Fuel supply pipes choked or clogged Restore the adequate fuel supply

Tank breather hole obstructed Restore the proper reservoir aeration

Level in chamber too low Restore the correct level in the chamber (the float must be par-

allel to the upper cover contact plane, that is the throttle valve

membrane cover)

Engine tends to cut-off at idle

ENGINE STOP IDLING

Possible Cause

Operation

Air calibrated holes in carburettor blocked Dismantle, wash with solvent and dry with compressed air

Defective floating valve Check the proper sliding of the float and the functioning of the

valve

Level in chamber too high Restore the correct level in the chamber (the float must be par-

allel to the upper cover contact plane, that is the throttle valve

membrane cover)

The starter remains on Check that the small piston slides smoothly and check the au-

tomatic starter power supply; replace it if required

Air filter blocked or dirty. Dismantle the sponge, wash with water and shampoo, then

soak it in a mixture of 50% petrol and 50% of specific oil (Se­lenia Air Filter Oil), then hand dry without squeezing, allow to

drip dry and then reassemble.

Wrong idling adjustment Correctly adjust the engine idling and check the level of the

C.O.

Spark plug defective or faulty Replace the spark plug with one with the specified degree and

check the plug gap

Pressure too low at the end of compression Check the thermal group seals and replace worn components

Incorrect timing Time the system and check the timing system components

Vespa S 50 4T 4V (2008) Troubleshooting

TROUBL - 47

High fuel consumption

EXCESSIVE FUEL CONSUMPTION

Possible Cause Operation

Air filter blocked or dirty. Dismantle the sponge, wash with water and shampoo, then

soak it in a mixture of 50% petrol and 50% of specific oil (Se­lenia Air Filter Oil), then hand dry without squeezing, allow to

drip dry and then reassemble.

The starter remains on Check that the starter runs correctly and it is properly powered

Loose nozzles Check the maximum and minimum nozzles are adequately

fixed in their fittings

Incorrect float level Check and restore the correct fuel level in the chamber

Transmission and brakes

Clutch grabbing or performing inadequately

IRREGULAR CLUTCH PERFORMANCE OR SLIPPAGE

Possible Cause Operation

Faulty clutch Check that there is no grease on the masses. Check that the

clutch mass faying surface with the bell is mainly in the centre
with equivalent characteristics on the three masses. Check that

the clutch casing is not scored or worn in an anomalous way

Insufficient braking

INEFFICIENT BRAKING

Possible Cause

Operation

Worn brake pads or shoes Replace the brake pads or shoes and check for brake disk or

drum wear conditions.

Air bubbles inside the hydraulic braking system Carefully bleed the hydraulic braking system, (there must be

no flexible movement of the brake lever).

Brake disc or drum deformed Use a dial gauge to check the levelness of the disk with the

wheel correctly fitted and the concentricity of the rear drum;

check the brake disc screws are locked

Fluid leakage in hydraulic braking system Elastic fittings, piston seals or brake pump breakdown, replace

Excessive backlash in the rear brake control cable Adjust backlash with the appropriate adjuster on the shoe con-

trol lever

The brake fluid has lost its properties Replace the front brake fluid and top up to the correct level in

the pump

Return spring broken Replace spring.

Shoe control bolt not lubricated Lubricate with Z2 grease.

Brakes overheating

BRAKES OVERHEATING

Possible Cause

Operation

Defective plunger sliding Check calliper and replace any damaged part.

Brake disc or drum deformed Use a dial gauge to check the levelness of the disk with the

wheel correctly fitted and the concentricity of the rear drum;

check the brake disc screws are locked

Troubleshooting Vespa S 50 4T 4V (2008)

TROUBL - 48

Electrical system

Battery

BATTERY

Possible Cause Operation

The battery is the electrical device in the system that requires

the most frequent inspections and thorough maintenance.

The battery is the electrical device in the system that requires
the most frequent inspections and thorough maintenance. If the
vehicle is not used for some time (1 month or more) the battery

needs to be recharged periodically. The battery runs down
completely in the course of 5 ÷ 6 months. If the battery is fitted
on a motorcycle, be careful not to invert the connections, keep­ing in mind that the black earth wire is connected to the negative
terminal while the red wire is connected to the terminal marked

+.

Turn signal lights malfunction

ELECTRICAL SYSTEM MALFUNCTION

Possible Cause Operation

Turn indicators do not turn on Check turn indicators device and/or wiring as described in the

«Electrical system» chapter.

Steering and suspensions

Heavy steering

STEERING HARDENING

Possible Cause

Operation

STEERING HARDENING Check the tightening of the top and bottom ring nuts. If irregu-

larities continue in turning the steering even after making the
above adjustments, check the seats in which the ball bearings
rotate: replace them if they are recessed or if the balls are flat-

tened.

Excessive steering play

EXCESSIVE STEERING CLEARANCE

Possible Cause

Operation

Excessive steering clearance Check the tightening of the top ring nut. If irregularities continue

in turning the steering even after making the above adjust-

ments, check the seats in which the ball bearings rotate: re-

place if they are recessed.

Noisy suspension

NOISY SUSPENSION

Possible Cause

Operation

Noisy suspension If the front suspension is noisy, check: that the front shock ab-

sorber works properly and the ball bearings are good condition.

Vespa S 50 4T 4V (2008) Troubleshooting

TROUBL - 49

Possible Cause Operation

In conclusion, check the tightening torque of the wheel hub, the
brake calliper, the shock absorber disk in the attachment to the

hub and the steering tube.

Check that the swinging arm connecting the engine to the

chassis and the rear shock absorber work properly

Suspension oil leakage

OIL LEAKAGE FROM SUSPENSION

Possible Cause Operation

Oil leakage from suspension Replace the damper.

Troubleshooting Vespa S 50 4T 4V (2008)

TROUBL - 50

INDEX OF TOPICS

ELECTRICAL SYSTEM ELE SYS

Instruments and warning lights control board

INSTRUMENT BOARD - WARNING LIGHTS AND INSTRUMENT PANEL

Specification Desc./Quantity

1 Left turn indicator warning light 12V - 2W
2 High-beam warning light 12V - 1.2W
3 Fuel gauge
4 Instrument panel lighting bulbs 12V - 1.2W
5 Headlight warning light 12V 1.2W
6 Low fuel warning light 12V - 1.2W
7 Right turn indicator warning light 12V - 2W
8 Instrument panel lighting bulbs 12V - 2W
9 Pre-set warning light

Checks and inspections

In case the cause of ignition failure or malfunction
cannot be easily identified at sight, first of all re­place the control unit by another one in operating
conditions.
Remember that the engine must be off to discon­nect and replace the control unit.
If after replacement the vehicle starts properly, the
control unit is failing and must be replaced.

If the failure persists, check the generator and the
stator components as follows:
After visually checking the electrical connections,
use a specific tester to measurement the stator
winding and the pickup (see table).
If any failure is found after checking the loading coil
and the pick-up, replace the stator and the dam-

aged parts.

Electrical system Vespa S 50 4T 4V (2008)

ELE SYS - 52

Disconnect the connector on the flywheel cover
and measure the resistance between either con­tact and the earthing.

Specific tooling

020331Y Digital multimeter

PICK-UP CHECK

Specification Desc./Quantity

1 1) Brown cable and earth ~ 170 Ω

STATOR WINDING CHECK

Specification Desc./Quantity

1 1) Black cable and earth ~ 1 Ω

Ignition circuit

All the control operations of the system that require the disconnection of cables (checks of the connec­tions and the devices making up the ignition circuit) must be done with the engine off: if this is not done,
the controls might be irretrievably damaged.

No spark plug

Once the lack of power to the spark plug has been
detected and the LED indicates it can be ignited,
follow this procedure:

- Check the Pick-Up.

Disconnect the electronic starter connector and
check continuity between terminal No. 3 (Green)
and terminal No. 4 (Black).
The check includes the Pick-Up and its power line.
If a break in the circuit is found, check again the
flywheel and the engine earth connectors. If non­conforming values are measured, replace the
Pick-Up; otherwise, repair the cable harness.

Vespa S 50 4T 4V (2008) Electrical system

ELE SYS - 53

Electric characteristic

Pick - up resistance

approx. 170 Ohm

- HV primary coil check

Disconnect the electronic starter connector and
check continuity between terminal No. 3 (purple)
and terminal No. 1 (black) (see figure).
If non-conforming values are measured, check
again the HV coil primary directly on the positive
and negative terminals.
If the values are correct, repair the cable harness
or reset the connections; otherwise, replace the
HV coil

Electric characteristic

HV coil primary resistance

0.5 ÷ 0.6 Ohm

- HV coil secondary check

Disconnect the spark plug cap from the HV cable and measure the resistance between the HV cable
terminal and the HV coil negative terminal (see figure).
If non-conforming values are measured, replace the HV coil. To carry out a more complete diagnosis,
check the peak voltage with the multimeter adaptor.

Specific tooling

020409Y Multimeter adaptor - Peak voltage detection

Electric characteristic

HV coil secondary resistance

3000 ÷ 3600 Ohm

Electrical system Vespa S 50 4T 4V (2008)

ELE SYS - 54

- Pick-Up

Disconnect the ECU connector and connect the
positive terminal to connector No. 3 (green) and
the negative terminal to connector No. 4 (black).
Use the start-up system to run the engine and
measure the voltage produced by the Pick-Up.
Replace Pick-Up if non-conforming values are
measured.

N.B.
THE MULTIMETER MUST BE SELECTED TO DETECT

CONTINUOUS VOLTAGE.

Electric characteristic

Pick-Up voltage value

Pick-Up voltage value: > 2 Volt

- H.V. coil

With the electronic starter and the HV coil connec­ted to the system, measure the voltage of the coil
primary during the start-up test with the voltage
peak adaptor and by connecting the positive ter­minal to the ground lead and the negative terminal
to the coil positive connector.
If non-conforming values are measured, replace
the control unit.

THE POSITIVE TERMINAL OF THE HV COIL PRIMARY IS
BLACK.

Electric characteristic

High voltage coil voltage value

High voltage coil voltage value: > 100 Volt

Stator check

- Using a tester, check the resistance between the
brown-earth and black-earth terminal.

N.B.
VALUES ARE STATED AT AMBIENT TEMPERATURE. A

CHECK WITH THE STATOR AT OPERATING TEMPERA­TURE LEADS TO VALUES HIGHER THAN THOSE STATED.

Electric characteristic

Stator : Brown-earth

approx. 170 Ω (Pick-Up)

Stator : Black-earth

Vespa S 50 4T 4V (2008) Electrical system

ELE SYS - 55

~ 1 Ω (Stator)

Voltage regulator check

A malfunction in the voltage regulator might cause the following problems depending on the type of
fault:

1) Bulbs burned out (regulator in short circuit).

2) Malfunction of the lighting system and the electric starter (regulator interrupted).

3) Battery not recharging.

4) Turn indicators not working.
The regulator is earthed through the electrical system, so the regulator body does not earth the circuits
inside the regulator.
There must be insulation between each regulator terminal and the regulator body (use the tester to
check electric resistance).

2) LIGHTS AND STARTER NOT WORKING
Gain access to the voltage regulator by removing
the plastic cover on the legshield; start the engine
and keep running it at idle speed.
Connect the tester positive probe to terminal No.
1 (yellow cable) and the negative probe to terminal
No. 2 (black cable); check if there is voltage.
If there is voltage, check that the light remote con­trol and its excitation line, coming from the elec­tronic starter (sky blue PIN 7 - purple PIN 3) work
properly. Check the cable harness from the light
switch to the remote control and whether the
switch works properly .
If no voltage is detected, try connecting the nega­tive probe directly to earth; if voltage is detected
with this operation, check the earth wiring of the
regulator; otherwise, replace the regulator be­cause it is failing.
As a last check, the voltage supplied by the stator
can be measured:

- Disconnect the regulator connector and place a
tester to detect alternating voltage between the
Blue cable (4) and the ground connection (see fig­ure).

Electrical system Vespa S 50 4T 4V (2008)

ELE SYS - 56

- Voltage supplied at 2000 rpm must be about 25
÷ 35V.
If no value is obtained even with this test, replace
the regulator because it is obviously failing.

N.B.
TO MEASURE THE ABOVE VOLTAGE USE AN ANALOGUE

TESTER THAT CAN MEASURE ALTERNATING VOLTAG­ES AND KEEP THE ENGINE AT IDLE TO HAVE AN ALTER­NATING VOLTAGE OF A FREQUENCY AS CLOSE AS
POSSIBLE TO 50HZ SO AS TO DETECT THE EFFICIENT
VOLTAGE VALUE SUPPLIED BY THE REGULATOR
(ABOUT 12V).

Recharge system voltage check

3) BATTERY NOT RECHARGING
A failure in the direct current section of the voltage
regulator may cause the following problems de­pending on the type of fault:

a) Protection fuse blows due to overvoltage
(regulator in short circuit) and consequently
the battery fails to recharge.
b) Battery fails to recharge (regulator interrup­ted).
Measures

a) Protection fuse blows (regulator in short circuit).
Check that the cable harness going from the pro­tection fuse to the key switch is not damaged,
which may cause a short circuit to ground (thus
preventing damaging the regulator).
Afterwards measure the resistance between con­tact 3 (Orange) and contact 2 (Black) of the voltage
regulator (with connector disconnected)
If the value measured is far from that indicated,
replace the regulator because it is in short circuit.
b) Battery fails to recharge (regulator interrupted).
To check if there is any failure in the voltage reg­ulator recharge section, first connect 2 testers to
the battery (one to detect voltage and the other to
detect current) as indicated in the second figure
and follow the procedure below:

Vespa S 50 4T 4V (2008) Electrical system

ELE SYS - 57

Start the engine (temporarily connect the red cable
to the battery positive terminal in order to avoid
damaging the device that measures current).
Check that there is a 13V voltage minimum (bat­tery charged) and a recharge current of 1.5 ÷ 2A
with the lighting system but the starter disabled. To
disable the lighting system, remove the light re­mote control.
As the engine rpm increases, so do the current and
the recharge voltage; with rpm over 4000 there
must be a recharge current of about 4.5A; enabling
both the lighting system and the starter, the stop
light and if the horn is powered, current values ≥
5A and a voltage value of 14 ÷ 14.5V ( regulator
threshold voltage) can be found.

If values other than those above are detected,
replace the regulator; contrariwise, check the
cable harness and the connections.

Electric characteristic

Voltage regulator resistance

~ 8 MΩ

Turn signals system check

4) TURN INDICATORS NOT WORKING
If the turn indicators do not work, do the following:

- Remove the regulator connector and place the
tester probes between the orange cable (3) and
the black cable (2).

- Turn the key switch to ON and check that the
battery is getting voltage. If no voltage is detected,
repeat the test now between the orange cable and
the ground lead. If there is no voltage even after
this operation, check the cable harness and the
contacts of the key switch and the battery. Con­versely, if battery voltage is detected (black cable),
check the regulator ground cable harness.

Electrical system Vespa S 50 4T 4V (2008)

ELE SYS - 58

- If the above tests have positive results, jump con­tacts 5 (blue/black) and 3 (white) on the connector,
set the key switch to ON and turn the turn indicator
switch to the left and right to see when the lights
are steadily on (as they are directly powered by the
battery).
If even after this operation the turn indicators fail
to turn on, check that the wiring is not damaged
and the switch works properly. If these last two
tests have a positive result, replace the regulator
because it is certainly not functioning properly.

Specific tooling

020331Y Digital multimeter

Connectors

ELECTRONIC STARTER

SECTION "A"

1. HV COIL CONTROL

2. KEY SWITCH CONTACTS TO GROUND

3. HV COIL POSITIVE

SECTION "B"

1. KEY POSITIVE

2. STARTER POWER SUPPLY

3. PICK UP SIGNAL

4. GROUND

5. SOLENOID VALVE

6. NTC TEMPERATURE SENSOR

7. LIGHT REMOTE CONTROL

8. DIAGNOSIS SOCKET

Vespa S 50 4T 4V (2008) Electrical system

ELE SYS - 59

VOLTAGE REGULATOR

1. LIGHTING SYSTEM POWER SUPPLY (al­ternating)

2. GROUND

3. BATTERY POSITIVE

4. FROM FLYWHEEL (alternating)

5. TURN INDICATORS

Electrical system Vespa S 50 4T 4V (2008)

ELE SYS - 60

INDEX OF TOPICS

ENGINE FROM VEHICLE ENG VE

Exhaust assy. Removal

- Remove the 2 fixing nuts from the manifold to the

head

- Undo the 2 screws fixing the muffler to the hous-

ing; then remove the whole muffler paying atten­tion to the interference between its supporting
bracket and the cooling cover.

Removal of the engine from the vehicle

Removing the engine from the chassis

-Disconnect the battery.

-Remove the muffler assembly.

- Remove the rear wheel.

- Remove the rear brake mechanical transmission.

-Disconnect the electric terminals.

-Remove the throttle grip transmission.

- Disconnect the tubing (petrol-vacuum operated cock control).

- Disconnect the swinging arm on the engine side

- Disconnect the rear shock absorber lower clamping

WARNING

Be very careful when handling fuel.

CAUTION

When installing the battery, first attach the positive cable and then the negative cable.

WARNING

Wear safety goggles when using hitting tools.

Engine from vehicle Vespa S 50 4T 4V (2008)

ENG VE - 62

INDEX OF TOPICS

ENGINE ENG

Automatic transmission

Transmission cover

- Remove the 12 fixing screws.

- Remove the oil filling cap and then slide out the

cover.
If this operation is carried out directly on the vehi­cle, it is necessary to remove the transmission
cooling coupling and the air filter housing retain­ers.

N.B.
USE A MALLET ON THE APPROPRIATE COUPLINGS TO

REMOVE THE COVER.

Kickstart

-To remove the start up pinion push the starter

lever to facilitate extracting the pinion.

-Remove the kick-start screw and lever.

-Remove the Seeger ring and the washer indica-

ted in the figure.

-Pull out the toothed sector.

WARNING
THE SECTOR KEEPS THE SPRING SET, BE CAREFUL SO

AS NOT TO CAUSE ANY ACCIDENTS

Air duct

- To remove the intake throat on the transmission

cover, just remove the three fixing screws indica­ted in the figure.

Engine Vespa S 50 4T 4V (2008)

ENG - 64

Removing the driven pulley shaft bearing

- Slightly heat the crankshaft from the inside side
to avoid damaging the coated surface and use the
driven pulley shaft or a pin of the same diameter
to remove the bearing.

N.B.
IN CASE OF DIFFICULTY A STANDARD 8MM-INSIDE DI-

AMETER EXTRACTOR CAN BE USED.

Refitting the driven pulley shaft bearing

Refit the bearing with the aid of a bushing with the same diameter as the external plate of the bearing
after slightly heating the crankcase from the inside.

N.B.

WHEN REFITTING, ALWAYS REPLACE THE BEARING WITH A NEW ONE.

CAUTION

WHEN REMOVING/REFITTING THE BEARING, TAKE CARE NOT TO DAMAGE THE COVER
PAINTED SURFACE.

Removing the driven pulley

- Lock the clutch bell housing with the specific tool.

- Remove the nut, the clutch bell housing and the
whole of the driven pulley assembly.

N.B.
THE UNIT CAN ALSO BE REMOVED WITH THE DRIVING

PULLEY MOUNTED.

Specific tooling

020565Y Flywheel lock calliper spanner

Vespa S 50 4T 4V (2008) Engine

ENG - 65

Inspecting the clutch drum

- Check that the clutch bell is not worn or damaged.

- Measure the inner diameter of the clutch bell.

Characteristic

Clutch bell diameter/standard value

Ø 107+0.2 +0 mm

Clutch bell diameter/max. value allowed after
use

Ø 107.5 mm

Eccentricity measured /max.

0.20 mm

Removing the clutch

- Equip the tool with long pins screwed into position

«A» from the outside, insert the entire driven pulley
in the tool and have the central screw make con­tact.

CAUTION
THE TOOL WILL BE DEFORMED IF THE CENTRAL SCREW

IS TIGHTENED UP TOO FAR.

- Using a 34 mm socket wrench remove the clutch

locking nut.

- Loosen the central screw by undoing spring of

the driven pulley unit

- Separate the components.

Specific tooling

020444Y Tool for fitting/ removing the driven
pulley clutch

Engine Vespa S 50 4T 4V (2008)

ENG - 66

Inspecting the clutch

- Check the thickness of the clutch mass friction
material.

- The masses must not show traces of lubricants;
otherwise, check the driven pulley unit seals.

N.B.
UPON RUNNING-IN, THE MASSES MUST EXHIBIT A CEN-

TRAL FAYING SURFACE AND MUST NOT BE DIFFERENT
FROM ONE ANOTHER.
VARIOUS CONDITIONS CAN CAUSE THE CLUTCH TO
TEAR.

CAUTION
DO NOT OPEN THE MASSES USING TOOLS TO PREVENT

A VARIATION IN THE RETURN SPRING LOAD.

Characteristic

Check minimum thickness

1 mm

Pin retaining collar

- Remove the collar with the aid of 2 screwdrivers.

- Remove the three guide pins and the mobile half
pulley.

Vespa S 50 4T 4V (2008) Engine

ENG - 67

Removing the driven half-pulley bearing

- Remove the roller bearing with the special ex-

tractor inserted from the bottom of the fixed half­pulley.

CAUTION
POSITION THE HOLDING EDGE OF THE EXTRACTION PLI-

ERS BETWEEN THE END OF THE BEARING AND THE
BUILT IN SEALING RING.

Specific tooling

001467Y029 Bell for bearings, O.D. 38 mm

- Remove the ball bearing retention snap ring.

- Expel the ball bearing from the side of the clutch

housing by means of the special tool.

N.B.
PROPERLY SUPPORT THE HALF-PULLEY SO AS NOT TO

DEFORM THE SLIDING SURFACE OF THE DRIVING BELT

Specific tooling

020376Y Adaptor handle
020363Y 20-mm guide

Inspecting the driven fixed half-pulley

- Check that there are no signs of wear on the work

surface of the belt. If there are, replace the half­pulley..

- Make sure the bearings do not show signs of un-

usual wear.

- Measure the external diameter of the pulley bush-

ing.

Characteristic

Stationary driven half-pulley/Standard diame­ter

Ø 33.965 to 33.985 mm

Stationary driven half-pulley / Minimum diam­eter admitted after use

Ø 33.96 mm

Engine Vespa S 50 4T 4V (2008)

ENG - 68

Inspecting the driven sliding half-pulley

- Remove the 2 inner sealing rings and the two O­rings.

- Measure the inside diameter of the mobile half­pulley bushing.

Characteristic

Mobile driven half-pulley/ Maximum diameter
allowed

Ø 34.08 mm

- Check the belt contact surfaces.

- Insert the new oil seal and O-rings on the mobile
half-pulley.

- Fitting the half-pulley on the bushing.

Recommended products

AGIP GREASE SM 2 Grease for the C-ring of
the tone wheel

Soap-based lithium grease containing NLGI 2 Mo­lybdenum disulphide; ISO-L-XBCHB2, DIN
KF2K-20

- Make sure the pins and collar are not worn, reassemble the pins and collar.

- Use a greaser with a curved spout to lubricate the driven pulley unit with around 6 g of grease. This
operation must be done through one of the holes inside the bushing until grease comes out of the
opposite hole. This procedure is necessary to prevent the presence of grease beyond the O-ring.

Recommended products

AGIP GREASE SM 2 Grease for the C-ring of the tone wheel

Soap-based lithium grease containing NLGI 2 Molybdenum disulphide; ISO-L-XBCHB2, DIN KF2K-20

Refitting the driven half-pulley bearing

- Fit a new ball bearing with the specific tool.

- Fit the ball bearing retention snap ring.

- Fit the new roller bearing with the wording visible
from the outside.

CAUTION
PROPERLY SUPPORT THE HALF-PULLEY TO PREVENT

DAMAGE TO THE THREADED END WHILE THE BEARINGS
ARE BEING FITTED.

Specific tooling

020376Y Adaptor handle

Vespa S 50 4T 4V (2008) Engine

ENG - 69

020456Y Ø 24 mm adaptor
020362Y 12 mm guide
020171Y Punch for Ø 17 mm roller case

Inspecting the clutch spring

- Check that the contrast spring of the driven pulley

does not show signs of deformation

- Measure the free length of the spring

Characteristic

Standard length

118 mm

Minimum length allowed after use

XXXX

- Check the thickness of the clutch mass friction

material.

-The masses must not show traces of lubricants;

otherwise, check the driven pulley unit.

N.B.
UPON RUNNING-IN, THE MASSES MUST EXHIBIT A CEN-

TRAL CONTACT SURFACE AND MUST NOT BE DIFFER­ENT FROM ONE ANOTHER. VARIOUS CONDITIONS CAN
CAUSE THE CLUTCH TO TEAR.

CAUTION
DO NOT OPEN THE MASSES USING TOOLS SO AS TO

PREVENT A VARIATION IN THE RETURN SPRING LOAD.

Characteristic

Minimum thickness permitted:

1 mm

Refitting the clutch

- Preassemble the driven pulley group with spring,

sheath and clutch.

- Position the spring with the sheath

- Insert the components in the tool and preload the

spring being careful not to damage the plastic
sheath and the end of the threaded bar.

Engine Vespa S 50 4T 4V (2008)

ENG - 70

- Reassemble the nut securing the clutch and tight­en to the prescribed torque.

CAUTION
SO AS NOT TO DAMAGE THE CLUTCH NUT USE A SOCK-

ET WRENCH WITH SMALL CHAMFER.
CAUTION
POSITION THE NON-CHAMFERED SURFACES OF THE

NUT IN CONTACT WITH THE CLUTCH

Locking torques (N*m)

Nut locking clutch unit on pulley 55 ÷ 60 Nm

Refitting the driven pulley

-Refit the driven pulley assembly, the clutch bell
and the nut, using the specific tool.

Specific tooling

020565Y Flywheel lock calliper spanner

Locking torques (N*m)

Driven pulley shaft nut 40 to 44 Nm

Drive-belt

- Make sure the driving belt is not damaged and
does not have cracks in the toothed grooves.

- Check the width of the belt.

Characteristic

Transmission belt/Minimum width

17.5 mm

Vespa S 50 4T 4V (2008) Engine

ENG - 71

Removing the driving pulley

- Lock the driving pulley using the appropriate tool.

- Remove the central nut with the related washer,

then remove the drive and the plastic fan.

- Remove the stationary half-pulley.

- Remove the belt, washer and remove the mobile half-pulley with its bushing, being careful that the
rollers and contrast plate fitted loosely on it do not come off.

Specific tooling

020451Y Starting ring gear lock

Inspecting the rollers case

1) Check that the bushing and the sliding rings of

the mobile pulley do not show signs of scoring or
deformation.

2) Check the roller running tracks on the contact

pulley; there must not be signs of wear and check
the condition of the contact surface of the belt on
the half-pulleys (mobile and stationary).

3) Check that the rollers do not show signs of

marked facetting on the sliding surface and that
the metallic insert does not come out of the plastic
shell borders.

4) Check the integrity of the sliding blocks of the

contact plate.

- Check that the internal bushing shown in the fig-

ure is not abnormally worn and measure inside
diameter «A».

- Measure outside diameter «B» of the pulley slid-

ing bushing shown in the figure.

CAUTION
DO NOT LUBRICATE OR CLEAN THE BUSHING.

Characteristic

Driving pulley / Maximum diameter:

Engine Vespa S 50 4T 4V (2008)

ENG - 72

20.12 mm

Driving pulley/ Standard diameter:

20.021 mm

Driving pulley bushing/ Diameter maximum:

XXX mm

Driving pulley bushing/ Standard diameter:

20 -0.020/-0.041mm

Refitting the driving pulley

- Manually move the movable driven half-pulley
away by pulling it towards the clutch unit and insert
the belt observing the direction of rotation of the
first fitting.

N.B.
IT IS GOOD PRACTICE ALWAYS TO FIT THE BELT SO

THAT THE WORDS CAN BE READ IN CASE IT DOES NOT
SHOW A FITTING SIDE.

- Refit the components of the assembly (roller con­tainer assembly with bushing, limiting washer, sta­tionary half-pulley, cooling fan belt with drive,
washer and nut).

- With the specific tool, tighten the lock nut to 20
Nm and then perform a final 90° locking in order to
prevent the rotation of the driving pulley.

N.B.
REPLACE THE NUT WITH A NEW ONE AT EVERY REFIT
CAUTION
UPON FITTING THE DRIVING PULLEY UNIT IT IS OF UT-

MOST IMPORTANCE THAT THE BELT IS FREE INSIDE IN
ORDER TO AVOID WRONG TIGHTENING AND CONSE­QUENTLY DAMAGING THE CRANKSHAFT KNURLING.

Specific tooling

020451Y Starting ring gear lock

Locking torques (N*m)

Crankshaft pulley nut 18 to 20 + 90° Nm

Vespa S 50 4T 4V (2008) Engine

ENG - 73

Refitting the transmission cover

- Check the following for wear: toothed section,

toothed section shaft, cover seat bushing, pinion
shaft and its seating in the crankcase and the re­turn spring.

- Remove the damaged components.

- Grease the spring.

- Remove the toothed sector and load the spring

with an appropriate tool.

- Refit the washer, the Seeger and the Kick-start

lever.

Recommended products

AGIP GREASE MU3 Grease for odometer
transmission gear case

Soap-based lithium grease with NLGI 3; ISO-L­XBCHA3, DIN K3K-20

- Insert the pinion in its seating by pushing the starter lever.

- Fit the intake throat and tighten the 3 screws.

-Make sure the oil sump presents centring dowels

and sealing gaskets.

- Replace the cover tightening the 12 screws to the

prescribed torque.

-Refit the oil filling cap.

Locking torques (N*m)

Transmission cover screws 11 ÷ 13 Nm

End gear

Engine Vespa S 50 4T 4V (2008)

ENG - 74

Removing the hub cover

• Remove the transmission cover

• Remove the clutch assembly

• Discharge the rear hub oil.

• Remove the 5 screws indicated in the figure.

• Remove the hub cover with driven pulley shaft.

See also

Refitting the clutch

Removing the wheel axle

- Remove the intermediate gear and the complete
gear wheel axle.

- When removing the intermediate gear pay atten­tion to the various shim adjustments.

Removing the wheel axle bearings

- Remove the oil seal and the Seeger ring.

- Remove the bearing by pushing from the outside
towards the inside of the gear compartment, using
the appropriate punch.

Specific tooling

020363Y 20-mm guide
020376Y Adaptor handle
020358Y 37x40-mm Adaptor

Vespa S 50 4T 4V (2008) Engine

ENG - 75

Removing the driven pulley shaft bearing

- Remove the Seeger ring inside the cover.

- Remove the oil seal from the outside.

- Remove the centring dowels and position the

cover on a plane.

- Position the special tool on the internal track of

the bearing and remove said bearing with the aid
of a press.

Specific tooling

020452Y Tube for removing and refitting the
driven pulley shaft

- Position the special tube on the internal raceway

of the bearing and from the shaft toothed side as
indicated in the figure. Expel the driven pulley shaft
with the aid of a press.

Specific tooling

020452Y Tube for removing and refitting the
driven pulley shaft

Inspecting the hub shaft

- Check the three shafts for wear or distortion of

the toothed surfaces, the bearing housings, and
the oil seal housings.

- In case of anomalies, replace the damaged com-

ponents.

- Check capacity ( A ) of the transmission gear

(wear, deformations, etc.)

- Check the pulley shaft seating: Superficial wear

( B ) may indicate irregularities in the crankcase
seatings or in the pulley shaft capacities

Inspecting the hub cover

- Check that the fitting surface is not dented or distorted.

- If faults are found, replace the hub cover.

Engine Vespa S 50 4T 4V (2008)

ENG - 76

Refitting the driven pulley shaft bearing

- Support the inner track of the bearing from the
outside of the hub cover with the specific tool posi­tioned under the press and insert the driven pulley
axle.

- Refit the oil seal flush with the cover.

Specific tooling

020452Y Tube for removing and refitting the
driven pulley shaft

• Heat the hub cover and insert the bearing with
the specific punch.

• Fit the snap ring with the concave or radial part
on the bearing side.

N.B.
FIT THE BALL BEARING WITH THE SHIELD FACING THE

OIL SEAL.

Specific tooling

020151Y Air heater
020376Y Adaptor handle
020439Y 17 mm guide
020358Y 37x40-mm Adaptor

Refitting the wheel axle bearing

- Heat the half crankcase on the transmission side
using a thermal gun.

- After lubricating its outer strip, insert the bearing
with the special adapter with the aid of a hammer.

- Refit the Seeger ring and the oil seal using the 42
x 47 mm adapter and the handle.

Specific tooling

020151Y Air heater
020376Y Adaptor handle
020363Y 20-mm guide
020359Y 42x47-mm Adaptor

Vespa S 50 4T 4V (2008) Engine

ENG - 77

Refitting the ub cover

- Refit the whole wheel axle.

- Refit the intermediate gear paying attention to the

two shim washers.

- Apply LOCTITE 510 for surfaces to the hub cov-

ers and refit the same with driven pulley shaft.

- Refit the 5 screws and tighten them to the speci-

fied torque.

N.B.
CLEAN THE CONTACT SURFACES OF THE HUB COVER

AND THE HALF CRANKCASE OF RESIDUE FROM PREVI­OUS GASKETS BEFORE APPLYING A NEW ONE.

Locking torques (N*m)

Locking torque: 11 to 13 Nm

Flywheel cover

Cooling hood

- Remove the manifold and the carburettor undo-

ing the 2 fixing screws on the head

- Remove the fastening clamp of the secondary air

pipe and disconnect it

- Remove the 4 front coupling screws (1 of them is

a knob) and the side fixing screw at the crankcase
base.

- Remove the 4 side screws

- Extract the 3 covers - Remove the cover sealing

gaskets on the head

- For refitting, repeat the removal steps but in re-

verse order

CAUTION
TAKE CARE TO CORRECTLY POSITION THE FLYWHEEL

CONNECTOR.
N.B.
WHEN REFITTING THE COVER, TAKE CARE NOT TO DAM-

AGE THE STATOR WIRING.

Engine Vespa S 50 4T 4V (2008)

ENG - 78

Cooling fan

- Remove the cooling fan by undoing the 3 screws
fixing it to the rotor

- When refitting the fan, pay attention that the
screw holes in the fan and the rotor coincide, then
tighten screws at the specified torque.

Removing the stator

- Remove the 2 Pick-Up screws and the 2 stator
fixing screws indicated in the figure.

- Remove the stator and its wiring.

Vespa S 50 4T 4V (2008) Engine

ENG - 79

Refitting the stator

- Refit the stator and flywheel carrying out the re-

moval procedure in reverse, tightening the retain­ers to the specified torque.

N.B.
THE PICK-UP CABLE MUST BE POSITIONED ADHERING

TO THE FUSION TONGUE ON THE CRANKSHAFT IN SUCH
A WAY AS TO AVOID BEING CRUSHED BY THE FAN COV­ER ASSEMBLY.

Locking torques (N*m)

Pick-up screws 3 ÷ 4 Stator screws 3 ÷ 4

Flywheel and starting

Removing the starter motor

- Undo the screw on the power positive contact

and disconnect the cable

- Undo the 2 screws fixing the starter motor to the

crankcase and recover the power wiring.

Engine Vespa S 50 4T 4V (2008)

ENG - 80

Removing the flywheel magneto

- Lock the rotation of the flywheel using the calliper
spanner.

- Remove the nut.

CAUTION
THE USE OF A CALLIPER SPANNER OTHER THAN THE

ONE SUPPLIED COULD DAMAGE THE STATOR COILS

- Extract the flywheel with the extractor.

Specific tooling

020565Y Flywheel lock calliper spanner
020162Y Flywheel extractor

Inspecting the flywheel components

- Check that the flywheel internal magnets are in
good conditions.

- Check that the flywheel splines exhibit no loos­ening.

- Check there are no deformations that may cause
rubbing on the stator and the Pick-Up.

- Check that the stator winding, its ferromagnetic
support and the pick-up are in good conditions.

Vespa S 50 4T 4V (2008) Engine

ENG - 81

Starter gear rim

- Check the toothing is level and in good conditions

Intermediate gear

- Check that the keying toothing on the crown and

the starter motor are in good conditions.

- Check that the Bendix opens and returns ade-

quately.

Refitting the flywheel magneto

- Refit the stator and the pick-up being careful to

pass the wiring through the appropriate crankcase
couplings.

- Refit the flywheel to the crankshaft being careful

to respect the keying, then lock rotation with the
specific tool and tighten the nut to the prescribed
torque.

N.B.
A VARIATION OF THE AIR GAP DISTANCE CAN LEAD TO

A VARIATION IN THE IGNITION ADVANCE SUCH AS TO
CAUSE PINGING, KNOCKING ETC.

Specific tooling

020565Y Flywheel lock calliper spanner

Locking torques (N*m)

Flywheel nut 52 ÷ 58

Engine Vespa S 50 4T 4V (2008)

ENG - 82

Refitting the starter motor

- Install the starter motor in its seating in the crank­case.

- Tighten the screw on the head side but do not
lock it, screw the second screw inserting the earth
cable (black), then tighten the 2 screws at the pre­scribed torque.

- Tighten the locking screw of the positive cable
(red) on the side contact.

N.B.
REFIT THE REMAINING PARTS AS DESCRIBED IN THE

CYLINDER HEAD, TIMING, LUBRICATION, FLYWHEEL
AND TRANSMISSION CHAPTERS.

Locking torques (N*m)

Starter screws 11 ÷ 13

Cylinder assy. and timing system

Removing the rocker-arms cover

- Remove the cooling covers

- Remove the 4 retainers of the tappet cover

- Remove the cover and the O-ring

- Remove the 3 screws and then remove the Blow­by cover

- Clean the nozzle labyrinth and the membrane
(replace it, if necessary), then remove the cover
unit.

Vespa S 50 4T 4V (2008) Engine

ENG - 83

Removing the timing system drive

- Temporarily loosen the tensioner central screw

and remove it together with the spring.

- Unscrew the 2 retainers indicated in the figure

and remove the chain tightener support being
careful to recover the sealing gasket.

N.B.
SHOULD THE GASKET NOT BE IN GOOD CONDITIONS,

REPLACE IT AFTER CAREFULLY CLEANING THE FAYING
SURFACE IN ORDER TO AVOID ENGINE OIL LEAKS

- Remove the driving pulley

- Remove the oil pump chain

- Remove the tappet cover

- Remove the central screw and the belleville

washer indicated in the figure and lock the cam­shaft crown with the specific tool.

N.B.
TO FACILITATE REMOVING THE HEAD COMPONENTS,

SET THE CRANKSHAFT TO THE TIMING POINT (TDC OF
THE COMPRESSION END).

Specific tooling

020565Y Flywheel lock calliper spanner

- Remove the camshaft control pulley and the washer below.

- Remove the pinion of the crankshaft timing control

- To remove the chain lower guiding pad, remove the head by pulling it upwards

N.B.

IT IS ADVISABLE TO MARK THE CHAIN IN ORDER TO ENSURE THAT THE DIRECTION OF RO­TATION IS MAINTAINED.

See also

Removing the rocker-arms cover
Removal
Removing the driving pulley

Engine Vespa S 50 4T 4V (2008)

ENG - 84

Removing the cam shaft

- Remove the limit screw of the rocking lever pins
shown in the figure.

- Remove the Seeger ring retaining the camshaft
bearing.

- Remove pins and rocking levers.

- Remove the calibrated pads

N.B.
MARK THE ASSEMBLY POSITION OF THE ROCKING LEV-

ERS IN ORDER TO AVOID MISPLACING THE INTAKE AND
DISCHARGE ENDS.

- Remove the entire camshaft with bearing using
the specific tool shown in the figure.

- Take out the camshaft bearing with the aid of the
specific tool, being careful to mount a screw on the
camshaft in order to protect its thread.

N.B.
IF A BEARING SEPARATES FROM THE CAMSHAFT, IT IS

ESSENTIAL TO FIT A NEW BEAR.

Specific tooling

020450Y Camshaft fitting/removal tool
004499Y Camshaft bearing extractor
004499Y001 Bearing extractor bell
004499Y002 Bearing extractor screw
004499Y006 Bearing extractor ring
004499Y027 Bearing extractor part

Vespa S 50 4T 4V (2008) Engine

ENG - 85

Removing the cylinder head

- Remove the cooling covers, the timing control,

the camshaft and the rocking levers.

- Remove the spark plug.

- Remove the 2 side fixings shown in the figure.

- Loosen the 4 head-cylinder fastening nuts in two

or three stages and in criss-cross fashion.

- Remove the head, the two centring dowels and

the gasket.

N.B.
IF NEEDED, THE HEAD MAY BE REMOVED WITH THE

CAMSHAFT, PINS AND ROCKING LEVERS WITHOUT RE­MOVING THE DRIVING PULLEY UNIT. REMEMBER TO
HOLD THE TIMING CHAIN WITH A PIECE OF METAL CA­BLE AND TO ADJUST THE CHAIN TIGHTENER UPON RE­FITTING.

Removing the valves

- Using the specific tool fitted with the part shown

in the figure, remove cotters, caps and valve
springs.

- Remove the oil seals with the appropriate tool.

Specific tooling

020431Y Valve oil seal extractor
020382Y Valve cotters equipped with part 012

removal tool

Engine Vespa S 50 4T 4V (2008)

ENG - 86

Removing the cylinder - piston assy.

- Remove the cylinder paying attention to the 2
cylinder centring dowels in the housing.

- Remove the cylinder base gasket.
To avoid damaging the piston, keep it fixed while
removing the cylinder.

- Remove the two stop rings, the wrist pin and the
piston.

- Remove the 3 piston rings.

N.B.
BE CAREFUL NOT TO DAMAGE THE PISTON RINGS DUR-

ING REMOVAL.

Inspecting the small end

- Measure the internal diameter of the small end
using an internal micrometer.

N.B.
IF THE DIAMETER OF THE ROD SMALL END EXCEEDS

THE MAXIMUM DIAMETER ALLOWED, SHOWS SIGNS OF
WEAR OR OVERHEATING REPLACE THE CRANKSHAFT
AS DESCRIBED IN THE "CRANKCASE AND CRANK­SHAFT" CHAPTER".

Characteristic

Max. diameter admitted: check the small end

13.030 mm

Standard diameter: check the small end

13 +0.025+0.015mm

Vespa S 50 4T 4V (2008) Engine

ENG - 87

Inspecting the wrist pin

- Measure the outer diameter of the gudgeon pin.

Characteristic

Standard diameter: gudgeon pin

13 -0-0.004mm

Minimum admissible diameter gudgeon pin

12.990 mm

Inspecting the piston

- Measure the diameter of the bearings on the pis-

ton.

Characteristic

Pin seat diameter

13 +0.005 +0.010 mm

- Carefully clean the seal housings.

- Measure the coupling clearance between the

sealing rings and the grooves using suitable sen­sors, as shown in the diagram.

- If the clearance is greater than that indicated in

the table, replace the piston.

N.B.
MEASURE THE CLEARANCE BY INSERTING THE BLADE

OF THE FEELER THICKNESS GAUGE FROM THE SECOND
SEAL SIDE.

Fitting clearance

Top piston ring - standard coupling clearance

0.03 ÷ 0.065 mm Top piston ring - maximum clear-

ance allowed after use 0.07 mm Middle piston
ring - standard coupling clearance 0.02 ÷ 0.055

mm Middle piston ring - maximum clearance al-

lowed after use 0.06 mm oil scraper ring - stand­ard coupling clearance 0.04 ÷ 0.16 mm oil scraper
ring - maximum clearance allowed after use

0.17 mm

Engine Vespa S 50 4T 4V (2008)

ENG - 88

Inspecting the cylinder

- Using a bore meter, measure the inner cylinder
diameter at three different points according to the
directions shown in the figure.

- Check that the coupling surface with the head is
not worn or misshapen.

- Pistons and cylinders are classified into catego­ries based on their diameter. The coupling is car­ried out in pairs (A-A, B-B, C-C, D-D).

Characteristic

Maximum allowable run-out:

0.05 mm

Inspecting the piston rings

- Alternately insert the three sealing rings into the cylinder, in the area where it retains its original di­ameter. Using the piston, insert the rings perpendicularly to the cylinder axis.

- Measure the opening, see figure, of the sealing rings using a thickness gauge.

- If any measurements are greater than specified, replace the piston rings.

N.B.

BEFORE REPLACING ONLY THE PISTON RINGS, ENSURE THAT THE CLEARANCE BETWEEN
THE PISTON RINGS AND THE PISTON RING GROOVES, AND BETWEEN THE PISTON AND THE
CYLINDER, IS AS SPECIFIED. IN ANY CASE, NEW PISTON RINGS USED IN COMBINATION WITH
A USED CYLINDER MAY HAVE DIFFERENT BEDDING CONDITIONS THAN THE STANDARD.

Vespa S 50 4T 4V (2008) Engine

ENG - 89

SEAL RINGS

Name Description Dimensions Initials Quantity

1st Compression ring 39 x 1 A 0.08 ÷ 0.20

2nd Compression ring 39 x 1 A 0.05 ÷ 0.20

Oil scraper ring 39 x 2 A 0.20 ÷ 0.70

1st Compression ring

1st Oversize

39.2 x 1 A 0.08 ÷ 0.20

2nd Compression ring

1st Oversize

39.2 x 1 A 0.05 ÷ 0.20

Oil scraper ring 1st

Oversize

39.2 x 2 A 0.20 ÷ 0.70

1st Compression ring

2nd Oversize

39.4 x 1 A 0.08 ÷ 0.20

2nd Compression ring

2nd Oversize

39.4 x 1 A 0.05 ÷ 0.20

Oil scraper ring 2nd

Oversize

39.4 x 2 A 0.20 ÷ 0.70

1st Compression ring

3rd Oversize

39.6 x 1 A 0.08 ÷ 0.20

2nd Compression ring

3rd Oversize

39.6 x 1 A 0.05 ÷ 0.20

Oil scraper ring 3rd

Oversize

39.6 x 2 A 0.20 ÷ 0.70

Removing the piston

- Install piston and wrist pin onto the connecting

rod, aligning the piston arrow the arrow facing to­wards the exhaust.

- Fit the pin stop ring onto the appropriate tool.

Specific tooling

020448Y Pin lock fitting tool

Engine Vespa S 50 4T 4V (2008)

ENG - 90

- With the opening in the position indicated on the
tool, set the lock ring into position in the tool with
the punch.

- Rest the tool on the piston paying attention that
the 90°chamfered side faces upwards as indicated
in the figure.

- Fit the gudgeon pin stop using the plug.

CAUTION
USING A HAMMER TO POSITION THE RINGS CAN DAM-

AGE THE LOCKING HOUSING.

Refitting the piston rings

- Fit the oil scraper ring starting from the spring,
taking care that the spring ends do not superim­pose. Fit the two piston rings so that their gaps and
that of the oil scraper ring are never aligned.

- Fit the 2nd sealing ring with the identifying letter
«T» facing towards the piston crown.

- Fit the 1st sealing ring with the reference letter
«T» facing towards the piston crown.

- Misalign the lining openings at 120° as shown in
the figure.

- Lubricate the components with engine oil.

N.B.
IN ORDER TO OBTAIN A GOOD BEDDING, THE 2 SEALING

PISTON RINGS ARE MADE OF CONE SHAPED CONTACT
SECTION TO THE CYLINDER. AS A RESULT IT IS IMPOR­TANT TO RESPECT THE FITTING INSTRUCTION TO AS­SEMBLY THE RINGS WITH THE "T" MARK FACING
UPWARDS.

Vespa S 50 4T 4V (2008) Engine

ENG - 91

Refitting the cylinder

- Insert the cylinder base gasket.

- Fit the cylinder as shown in the figure.

- The piston can be kept out of the housing plane

using the appropriate tool.

N.B.
BEFORE FITTING THE CYLINDER, CAREFULLY BLOW

OUT THE LUBRICATION DUCT AND OIL THE CYLINDER
BARREL.

Specific tooling

020288Y Fork to assemble piston on cylinder

If the four cylinder stud bolts should be replaced in this kind of engine, it is necessary to tighten the
head nuts strictly following the procedure below.
The procedure is different from that indicated in the vehicle manuals:
Head tightening nut (only to replace stud bolts) 6÷7 N*m + 135° + 90°
The 45° rotation reduction of the key is necessary to avoid stud bolt stretching.

Inspecting the cylinder head

- Using a trued bar check that the cylinder head

surface is not worn or distorted.

- Check that the camshaft and rocking lever pin

bearings show no signs of wear.

- Check that the cylinder head cover surface, the

intake manifold and the exhaust manifold are not
worn.

- It is advisable to replace the head if any failure is

found.

Characteristic

Maximum allowable run-out:

0.1 mm

Engine Vespa S 50 4T 4V (2008)

ENG - 92

Measure the camshaft bearing seats and rocking
lever support pins with a bore meter

HEAD CHECK

Specification Desc./Quantity

Standard diameter (mm) A Ø 32.015 ÷ 32.025 mm
Standard diameter (mm) B Ø 16.0 ÷ 16.018
Standard diameter (mm) C Ø 11.0 ÷ 11.018

Inspecting the timing system components

- Check that the guide shoe and the tensioner shoe
are not worn out.

- Ensure that the camshaft drive pulley, the chain
assembly and the sprocket wheel are not worn.

- If sings of wear are found, replace the parts. if the
chain, pinion or pulley are worn, replace the whole
assembly.

- Remove the central screw and the tensioner
spring. Check that the one-way mechanism is not
worn.

- Check the condition of the tensioner spring.

- If examples of wear are found, replace the whole
assembly.

Vespa S 50 4T 4V (2008) Engine

ENG - 93

Inspecting the valve sealings

- Clean the valve seats of any carbon residues.

- Using the Prussian blue, check the width of the

impression on the valve seat "V".

Characteristic

Standard value:

1 - 1.3 mm

Admissible limit:

1.6 mm

- If the impression width on the valve seat is larger than the prescribed limits, true the seats with a 45°
mill and then grind.

- In case of excessive wear or damages, replace the head.

- Insert the valves into the cylinder head.

- Alternatively check the intake and exhaust

valves.

- The test is carried out by filling the manifold with

petrol and checking that the head does not ooze
through the valves when these are just pressed
with the fingers.

Inspecting the valves

STANDARD VALVE LENGTH

Specification

Desc./Quantity

Inlet: standard length 74.9 mm

Outlet: standard length 74.35 mm

Engine Vespa S 50 4T 4V (2008)

ENG - 94

- Measure the diameter of the valve stems in the
three positions indicated in the diagram.

STANDARD DIAMETER

Specification Desc./Quantity

Inlet 3.970 ÷ 3.985 mm

drainage 3.960 ÷ 3.975 mm

MINIMUM DIAMETER PERMITTED

Specification Desc./Quantity

Inlet 3.958 mm

drainage 3.945 mm

- Calculate the clearance between valve and valve guide.

- Check the concentricity of the valve head by ar­ranging a dial gauge at right angle relative to the
valve head and rotate it on a "V" shaped abutment.

Characteristic

Admissible limit:

0.03 mm

- Check the deviation of the valve stem by resting
it on a «V» shaped abutment and measuring the
extent of the deformation with a dial gauge.

Characteristic

Limit values admitted:

0.1 mm

Vespa S 50 4T 4V (2008) Engine

ENG - 95

Inspecting the valve stem guide clearance

Measure the valve guides

VALVE GUIDE DIAMETER

Specification Desc./Quantity

Valve guide Standard diameter: 4 + 0.012 mm
Valve guide Maximum admissible diameter: 4 + 0.022 mm

- After measuring the valve guide diameter and the

valve stem diameter, check clearance between
guide and stem.

INLET

Specification

Desc./Quantity

Standard clearance 0.015 ÷ 0.042 mm

Admissible limit 0.06 mm

OUTLET

Specification

Desc./Quantity

Standard clearance 0.025 ÷ 0.052 mm

Admissible limit 0.07 mm

Engine Vespa S 50 4T 4V (2008)

ENG - 96

Refitting the valves

- Lubricate the valve guides with graphite grease.

- Place the lower caps of the valve spring on the
head.

- Use the punch to fit the 4 sealing rings one at a
time.

- Fit the valves, the springs and the upper caps.

- Using the appropriate tool, compress the springs
and insert the cotters in their seats.

Inspecting the cam shaft

- Inspect the cam shaft for signs of abnormal wear
on the cams.

Characteristic

Standard diameter - Bearing A:

Ø 12 +0.002 +0.010

mm Standard diameter - Bearing B:

Ø 16-0.015 -0.023 mm

Minimum diameter allowed - Bearing A:

Ø 11.98 mm

Minimum diameter allowed - Bearing B:

Ø 15.96 mm

-Using a gauge, measure the cam height.
Check the axial clearance of the camshaft

Vespa S 50 4T 4V (2008) Engine

ENG - 97

- If any of the above dimensions are outside the

specified limits, or there are signs of excessive
wear, replace the defective components with new
ones.

N.B.
A BALL BEARING IS FITTED ON BEARING «A»; CONSE-

QUENTLY, BEARING «B» IS THE MOST IMPORTANT AS IT
WORKS DIRECTLY ON THE HEAD ALUMINIUM

Characteristic

Standard height - Inlet

24.397 mm

Standard height - Outlet

23.996 mm

Fitting clearance

Maximum admissible axial clearance: 0.5 mm

- Measure the outside diameter of the rocking lever pins

- Check the rocker pins do not show signs of wear or scoring.

- Measure the internal diameter of each rocking lever.

- Check that the pad in contact with the cam is not worn.

ROCKING LEVERS AND PIN DIAMETER:

Specification

Desc./Quantity

Rocking levers - Inside diameter 11.015 ÷ 11.035 mm

Rocking levers - Pins diameter 10.977 ÷ 10.985 mm

Refitting the head and timing system components

- Fix the head on a workbench.

- Screw the tool to fit the camshaft fully down on the bearing's inner track.

- Fit the camshaft fully into its seating together with the bearing with the aid of a mallet.

- Remove the tool.

- Fit the head gasket after cleaning the faying surface carefully.

Engine Vespa S 50 4T 4V (2008)

ENG - 98

- Insert the head in the cylinder stud bolts and tighten the 4 fixing nuts to the prescribed torque.

Specific tooling

020450Y Camshaft fitting/removal tool

- Fit pins, inlet rocking lever and discharge rocking
lever.

- Lubricate the 2 rocking levers through the holes.

N.B.
IF A BEARING SEPARATES FROM THE CAMSHAFT, IT IS

ESSENTIAL TO FIT A NEW BEARING.

- Screw up the limit screw of the rocking lever pins
and tighten it to the prescribed torque.

- Reposition the Seeger ring retaining the cam­shaft

Locking torques (N*m)

Rocking lever shafts screw 3 ÷ 4

- Finish the head tightening following the proce­dure below: screw the four head nuts to an initial
torque at two crossed passes. Afterwards tighten
the nuts with 2 turns of 90° each to be done at two
crossed passes.

-Finish the tightening of the head to the crankcase
with the 2 side screws.

N.B.
SHOULD THE CRANKCASE OR THE CYLINDER STUD

BOLTS BE REPLACED, IT IS NECESSARY TO CARRY OUT
AN INITIAL TIGHTENING PLUS OTHER 3 TURNS OF 90°
EACH AT 3 CROSSED PASSES

Locking torques (N*m)

Head-cylinder stud bolt nuts: 6 ÷ 7 +135° +90° Nm

first fitting, upon refitting tighten again at 6 ÷ 7 90° +90°
Nm Head cover screws 8 ÷ 10 Nm

Vespa S 50 4T 4V (2008) Engine

ENG - 99

Refitting the timing chain

- Insert the timing chain pads in their correspond-

ing seatings, the screw and the spacer as indica­ted in the figure.

- Tighten to the prescribed torque and check the

tensioner pad moves adequately.

- Insert the timing pinion in driving shaft with the

chamfered side facing the insertion (towards the
main bearing).

- Loop the timing chain around the sprocket on the

crankshaft.

Locking torques (N*m)

Chain tensioner pad screw 5 ÷ 7 Nm

- Refit the spacer on the cam shaft.

- Rotate the engine so that the piston is at top dead

centre, using the reference marks on the flywheel
and the crankcase.

- With this operation, insert the chain on the cam-

shaft control pulley and make the reference notch
coincide with the point on the head.

- Fit the pulley onto the camshaft.

- Fit the belleville washer so that the outer rim

touches the pulley.

- Bring the screw closer but without reaching its

final locking point.

- Push the tensioner pad lightly so as to check the

correct timing.

- Use the specific tool to lock the camshaft crown

gear and tighten the screw.

- Adjust valve clearance.

- Replace the O-Ring on the tappet cover.

- Fit the tappet cover and lock it with the 4 fixing

screws indicated in the figure.

Specific tooling

020565Y Flywheel lock calliper spanner

Locking torques (N*m)

Engine Vespa S 50 4T 4V (2008)

ENG - 100