Piaggio Vespa WORKSHOP ET4 50 Workshop Manual

WORKSHOP MANUAL

633367

ET4 50

ET4 50

WORKSHOP

MANUAL

The descriptions and illustrations given in this publication are not binding. While the basic specifications
as described and illustrated in this manual 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

versions should be checked at the official Piaggio sales network.

"© Copyright 2007 - 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)

WORKSHOP MANUAL

ET4 50

This workshop manual has been drawn up by Piaggio & C. Spa to be used by the workshops of Piaggio­Gilera dealers. This manual is addressed to Piaggio service mechanics who are supposed to have a
basic knowledge of mechanics principles and of vehicle fixing techniques and procedures. Any important
changes made to the vehicles or to specific fixing operations will be promptly reported by updates to this
manual. Nevertheless, no fixing work can be satisfactory if the necessary equipment and tools are
unavailable. It is therefore advisable to read the sections of this manual relating to specific tools, along
with the specific tool catalogue.

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

ET4 50 Characteristics

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 spares 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 sizes. 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.

CHAR - 7

Characteristics ET4 50

Vehicle identification

VEHICLE IDENTIFICATION

Specification Desc./Quantity

Frame prefix ZAPC2610000001001

Engine prefix C261M

Dimensions and mass

DIMENSIONS AND MASS

Specification Desc./Quantity

Total unloaded kerb weight 105 Kg

Width 710 mm

Length 1780 mm

Wheelbase 1275 mm

Height 1090 mm

CHAR - 8

ET4 50 Characteristics

Engine

ENGINE

Specification Desc./Quantity

Type single-cylinder, four-stroke
Bore 39 mm

Stroke 41,8 mm

Cubic capacity 49.93 cm³

Compression ratio 11,5 ÷ 12 : 1

Timing system single overhead camshaft, driven by a chain to the left side.

Vacuum carburettor KEIHIN CVK Ø 18 mm

CO adjustment 3,2% ± 0,5

Engine idle 1900 ÷ 2000 rpm.

Air filter Sponge impregnated with fuel mixture (50% SELENIA air filter

Starting system electric starter/kickstarter

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

a chain. Mesh prefilter and centrifugal on the crankshaft

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

Max. power (crankshaft) 2,5 KW (3,4 CV) at 6500 rpm.

Cooling system forced coolant circulation system

Valve clearance (cold engine) intake 0.10 mm

WALBRO WP 16A

oil and 50% unleaded petrol).

ing of 95) with carburettor.

discharge 0.15 mm

Transmission

TRANSMISSION

Specification

Transmission With automatic expandable pulley variator, torque server, V

belt, automatic clutch, gear reduction unit.

Desc./Quantity

Capacities

CAPACITIES

Specification

Fuel tank (including ~ 2.3 l reserve) ~ 9l

Rear hub 80 cc

Engine oil ~ 850 cc

Desc./Quantity

Electrical system

ELECTRICAL COMPONENTS

Specification

Type of ignition Capacitive discharge type electronic ignition, with incorporated

Ignition advance variable, with microprocessor (before T.D.C.) 10° at 1800-2000 rpm

Spark plug Champion RG 4 PHP

Battery 12V-9Ah

Fuse 10A

Generator single-phase alternating current

Desc./Quantity

high voltage coil

26° at 5000-6000 rpm

Champion RG 4 HC

CHAR - 9

Characteristics ET4 50

Frame and suspensions

FRAME AND SUSPENSIONS

Specification Desc./Quantity

Type Unitised body made of stamped plate

Front suspension Single arm suspension with swinging arm articulated to the

Front suspension stroke 70 mm

Trail (suspension rebounded/compressed) 71/68 mm

Rear suspension Single hydraulic double-acting shock absorber, helicoidal co-

Rear suspension bump position 80 mm

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

axial spring

axial spring. Chassis engine support with swinging arm.

Brakes

BRAKES

Specification Desc./Quantity

Front brake Disc brake Ø 200 mm with hydraulic linkage (r.h brake lever).
Rear brake Drum brake Ø 110 mm with mechanical linkage.

Wheels and tyres

WHEELS AND TYRES

Specification

Front tyre dimension 100/80-10"

Rear tyre size 120/70-10"
Front tyre pressure: 1,3 bar
Rear tyre pressure: 1,8 ÷ 2 bar

Lightweight alloy wheels (front) 2,15" x 10"

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.

Desc./Quantity

Carburettor

50cc Version

Kehin

CARBURETTOR KEHIN

Specification

Manufacturer and Type KEHIN CVK 18

Type vacuum
Choke diameter Ø 18 mm
Maximum thrust 75

Minimum jet 35

Starter jet 42

Emulsioner Ø 2,1 mm

Tapered pin stamping NACA

Notches from the top the rod has no notches

Desc./Quantity

CHAR - 10

ET4 50 Characteristics

Specification Desc./Quantity

Fuel inlet hole Ø 1,2 mm

Starter piston protrusion 11 mm at 24°C

Tightening Torques

STEERING ASSEMBLY

Name Torque in Nm

Upper steering ring nut 30 ÷ 40
Lower steering ring nut 8 ÷ 10

Handlebar fastening 45 ÷ 50

FRAME ASSEMBLY

Name Torque in Nm

Engine-swinging arm bolt 33 ÷ 41

Floating arm-frame pin 44 ÷ 52

Shock absorber - chassis nut 20 ÷ 25

Shock absorber-engine nut 33 ÷ 41

Rear wheel nut 137 ÷ 152

Speedometer gear plate fixing screw 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

(°)Tighten these two bolts after tightening the shock absorber central upper nut.

N.B.

FOR INFORMATION ON SAFETY TIGHTENINGS, REFER TO CHAPTER «PRE-CONSIGNMENT
CHECKS».

FRONT BRAKE

Name

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

Torque in Nm

ENGINE ASSEMBLY

Name

Spark plug: 10 ÷ 15 Nm

Head cover screws 8 ÷ 10

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

Rocker-arm 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

Torque in Nm

CHAR - 11

Characteristics ET4 50

Name Torque in Nm

Oil decantation labyrinth sheet screws 7 ÷ 8

Oil pump crown screw 8 ÷ 10

Screws fixing oil pump to crankcase 5 - 6

Oil sump screws 8 ÷ 10 Nm

Inlet manifold screw 7 ÷ 9

Manifold/carburettor clamp screw 1,2 ÷ 1,5

Screws fixing cables to starter motor 1.5 ÷ 2.5

Starter motor 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 cover screws 11 ÷ 13

Wheel axle nut 115 ÷ 125

Crankcase half union screw 8 ÷ 10

*When new stud bolts are assembled, tighten them with 3 turns at 90° after the first tightening at 6-7
N·m, therefore 6-7 N·m + 90 ° + 90 ° + 90 °, in a crosswise manner.

Overhaul data

Assembly clearances

Cylinder - piston assy.

Name

Cylindre Ø C (39

±0,014)

Cylindre Ø C (39

±0,014)

Piston Ø P (38,968

±0,014)

CHAR - 12

PISTON AND CYLINDER MATING

Initials Cylinder Piston Play on fitting

A 38,986 ÷ 38,993 38,954 ÷ 38,961 0,025 ÷ 0,039
B 38,993 ÷ 39,000 38,961 ÷ 38,968 0,025 ÷ 0,039
C 39,000 ÷ 39,007 38,968 ÷ 38,975 0,025 ÷ 0,039

ET4 50 Characteristics

Name Initials Cylinder Piston Play on fitting

Piston Ø P (38,968

±0,014)

Cylindre 1st oversize Ø

C (39,2 ±0,014)

Cylindre 1st oversize Ø

C (39,2 ±0,014)

Piston 1st oversize Ø P

(39,168 ±0,014)

Piston 1st oversize Ø P

(39,168 ±0,014)

Cylindre 2nd oversize Ø

C (39,4 ±0,014)

Cylindre 2nd oversize Ø

C (39,4 ±0,014)

Piston 2nd oversize Ø P

(39,368 ±0,014)

Piston 2nd oversize Ø P

(39,368 ±0,014)

Cylindre 3rd oversize Ø

C (39,6 ±0,014)

Cylindre 3rd oversize Ø

C (39,6 ±0,014)

Piston 3rd oversize Ø P

(39,568 ±0,014)

Piston 3rd oversize Ø P

(39,568 ±0,014)

D 39,007 ÷ 39,014 38,975 ÷ 38,982 0,025 ÷ 0,039

A 1 39,186 ÷ 39,193 39,154 ÷ 39,161 0,025 ÷ 0,039

B1 39,193 ÷ 39,200 39,161 ÷ 39,168 0,025 ÷ 0,039
C 1 39,200 ÷ 39,207 39,168 ÷ 39,175 0,025 ÷ 0,039
D 1 39,207 ÷ 39,214 39,175 ÷ 39,182 0,025 ÷ 0,039
A 2 39,386 ÷ 39,393 39,354 ÷ 39,361 0,025 ÷ 0,039
B 2 39,393 ÷ 39,400 39,361 ÷ 39,368 0,025 ÷ 0,039
C 2 39,400 ÷ 39,407 39,368 ÷ 39,375 0,025 ÷ 0,039
D 2 39,407 ÷ 39,414 39,375 ÷ 39,382 0,025 ÷ 0,039
A 3 39,586 ÷ 39,593 39,554 ÷ 39,561 0,025 ÷ 0,039
B 3 39,593 ÷ 39,600 39,561 ÷ 39,568 0,025 ÷ 0,039
C 3 39,600 ÷ 39,607 39,568 ÷ 39,575 0,025 ÷ 0,039
D 3 39,607 ÷ 39,614 39,575 ÷ 39,582 0,025 ÷ 0,039

Piston rings

UPRATING TABLE

Name

1° Compression lining 39 x 1 A 0,08 ÷ 0,20
2° Compression lining 39 x 1 A 0,05 ÷ 0,20

Scraper ring lining 39 x 2 A 0,20 ÷ 0,70

1° Compression lining

1° greater

2° Compression lining

1° greater

Scraper ring lining 1°

greater

1° Compression lining

2° greater

2° Compression lining

2° greater

Scraper ring lining 2°

greater

1° Scraper ring lining 3°

greater

2° Scraper ring lining 3°

greates

Description Dimensions Initials Quantity

39,2 x 1 A 0,08 ÷ 0,20
39,2 x 1 A 0,05 ÷ 0,20
39,2 x 2 A 0,20 ÷ 0,70
39,4 x 1 A 0,08 ÷ 0,20
39,4 x 1 A 0,05 ÷ 0,20
39,4 x 2 A 0,20 ÷ 0,70
39,6 x 1 A 0,08 ÷ 0,20
39,6 x 1 A 0,05 ÷ 0,20

CHAR - 13

Characteristics ET4 50

Name Description Dimensions Initials Quantity

Scraper ring lining 3°

greates

39,6 x 2 A 0,20 ÷ 0,70

Crankcase - crankshaft - connecting rod

END PLAY BETWEEN DRIVING SHAFT AND CONNECTING ROD

Name

Transmission side half

shaft

Flywheel side half shaft 16 +0 -0.005 B

Connecting rod 14.8 +0.05 -0 C

Spacing tool 45,00 / assembly

Description Dimensions Initials Quantity

14 +0 -0.005 A

E

games D = 0,15 ÷ 0,30

Slot packing system

Shimming method for limiting the compression ra­tio

Rc = 11,5 ÷ 12

A = MEASUREMENT «A» (WITH PISTO AT T.D.C.)
B = MEASUREMENT «A» IS TO BE TAKEN WITHOUT ANY GASKET BETWEEN THE CRANKCASE

AND THE CYLINDER
C = FIT THE GASKET SHOWN IN THE TABLE ACCORDING TO SIZE «A»

CHAR - 14

ET4 50 Characteristics

N.B.

MEASUREMENT «A» IS A PISTON RECESS VALUE

The more the piston protrudes out of the plane generated by the top section of the cylinder, the thicker
the gasket to be applied (to recover the compression ratio) and vice-versa.

THICKNESS (IN FIBER)

Specification Desc./Quantity

CYLINDER HEIGHT 57,15 ± 0,05

HEAD GASKET THICKNESS (IN FIBER) 0,95 ± 0,06

MEASUREMENT 0,9 ± 0,05 BASE GASKET THICKNESS 0,4

MEASUREMENT 1 ± 0,05 BASE GASKET THICKNESS 0,5

THICKNESS (IN STEEL)

Specification Desc./Quantity

HEAD GASKET THICKNESS (steel) 0.3 ± 0.05

CYLINDER HEIGHT 57,15 ± 0,05
MEASUREMENT 0,20 ± 0,05 BASE GASKET THICKNESS 0,4
MEASUREMENT 0,30 ± 0,05 BASE GASKET THICKNESS 0,5

Products

Product

AGIP ROTRA 80W-90 Rear hub oil SAE 80W/90 Oil that exceeds the re­AGIP CITY HI TEC 4T Oil to lubricate flexible transmissions

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

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

AGIP GREASE MU3 Grease for odometer transmission gear

AGIP BRAKE 4 Brake fluid FMVSS DOT 4 Synthetic fluid

MONTBLANC MOLYBDENUM

GREASE

AGIP GREASE PV2 Grease for steering bearings, bolt seat-

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

TABLE OF RECOMMENDED PRODUCTS

Description Specifications

quirements of API GL3 specifications

(brakes, throttle control and odometer)

case

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

ings for swinging arms and contact sur­face of driven pulley spring (only pulley

side)

Soap-based lithium grease with NLGI 3;

Grease with molybdenum disulphide

Lithium soap and zinc oxide grease NLGI

spray grease with NLGI 2; ISO-L-XBCIB2

Oil for 4-stroke engines

creased adhesiveness

Synthetic oil

ISO-L-XBCHA3, DIN K3K-20

2; ISO-L-XBCIB2

CHAR - 15

INDEX OF TOPICS

TOOLING TOOL

ET4 50 Tooling

TOOLING

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

005095Y Engine support

008119Y009 Tube to assemble shafts and axles

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

Half rings

020004Y Punch for removing fifth wheels from

headstock

TOOL - 17

Tooling ET4 50

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

TOOL - 18

ET4 50 Tooling

Stores code Description

020288Y Fork to assemble piston on cylinder

020291y Valves assembly/disassembly tool

020306Y Punch for assembling valve seal rings

020329Y MityVac vacuum-operated pump

020330Y Stroboscopic light to check timing

020331Y Digital multimeter

TOOL - 19

Tooling ET4 50

Stores code Description

020332Y Digital rev counter

020333Y Single battery charger

020334Y Multiple battery charger

020335Y Magnetic support for dial gauge

020340Y Flywheel and transmission oil seals fitting

punch

TOOL - 20

020358Y 37x40-mm adaptor

ET4 50 Tooling

Stores code Description

020359Y 42x47-mm adaptor

020360Y Adaptor 52 x 55 mm

020362Y 12 mm guide

020363Y 20 mm guide

020364Y 25-mm guide

020376Y Adaptor handle

TOOL - 21

Tooling ET4 50

Stores code Description

020431Y Valve oil seal extractor

020432Y Tool to fit the start-up sector spring

020439Y 17 mm guide

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

020449Y Piston position check support

020450Y Camshaft fitting/removal tool

TOOL - 22

020451Y Drive pulley stop wrench

ET4 50 Tooling

Stores code Description

020452Y Tube for removing and refitting the driven

020456Y Ø 24 mm adaptor

020565Y Flywheel lock calliper spanner

pulley shaft

494929Y Exhaust fumes analyser

TOOL - 23

INDEX OF TOPICS

MAINTENANCE MAIN

ET4 50 Maintenance

Maintenance chart

AT 1000 KM OR 4 MONTHS

80'

Action

Hub oil - change
Valve clearance - check
Idle speed (*) - adjustment
Throttle lever - adjustment
Steering - adjustment
Brake control levers - greasing
Brake pads - check condition and wear
Brake fluid level - check
Safety locks - check
Electrical system and battery - check
Tyre pressure - check
Vehicle and brake test - road test
Emergency blockings (°) - Check

(*) Refer to rules «Adjusting the idle speed»
(°) Refer to predelivery operations

AT 6000 KM OR 12 MONTHS, 18000 KM OR 36 MONTHS, 30000 KM, AT 42000 KM, AT

54000 KM AND AT 66000 KM

70'

Action

Engine oil - replacement
Hub oil level - check
Oil filter (net filter) - clean
Variable speed rollers - check or replacement
Brake pads - check condition and wear
Brake fluid level - check
Electrical system and battery - check
Tyres condition and wear - Check
Tyre pressure - check
Vehicle and brake test - road test

AT 12000 OR 24 MONTHS AND AT 60000 KM

125'

Action

Engine oil - replacement
Hub oil level - check
Spark plug / electrode gap - check / replacement
Air filter - clean
Oil filter (net filter) - clean
Idle speed (*) - adjustment
Throttle lever - adjustment
Variable speed rollers - check or replacement
Driving belt - replacement
Odometer gear - greasing
Steering - adjustment
Brake control levers - greasing
Brake pads - check condition and wear
Brake fluid level - check
Transmission elements - lubrication
Emergency blockings (°) - Check
Suspensions - check
Electrical system and battery - check
Headlight - adjustment
Tyres condition and wear - Check
Tyre pressure - check
Vehicle and brake test - road test

MAIN - 25

Maintenance ET4 50

* Refer to rules
(°) Refer to predelivery operations

AT 24000 KM OR 48000 KM

160'

Action

Engine oil - replacement
Hub oil level - replacement
Spark plug / electrode gap - check / replacement
Air filter - clean
Oil filter (net filter) - clean
Valve clearance - check
Idle speed (*) - adjustment
Throttle lever - adjustment
Variable speed rollers - check or replacement
Driving belt - replacement
Cylinder ventilation system - check
Odometer gear - greasing
Steering - adjustment
Brake control levers - greasing
Brake pads - check condition and wear
Brake fluid level - check
Transmission elements - lubrication
Emergency blockings (°) - Check
Suspensions - check
Electrical system and battery - check
Headlight - adjustment
Tyres condition and wear - Check
Tyre pressure - check
Vehicle and brake test - road test

* Refer to rules
(°) Refer to predelivery operations

175'

Engine oil - replacement
Hub oil level - check
Spark plug / electrode gap - check / replacement
Air filter - clean
Oil filter (net filter) - clean
Idle speed (*) - adjustment
Throttle lever - adjustment
Variable speed rollers - check or replacement
Driving belt - replacement
Odometer gear - greasing
Steering - adjustment
Brake control levers - greasing
Brake pads - check condition and wear
Brake fluid hoses - replacement
Brake fluid level - check
Transmission elements - lubrication
Emergency blockings (°) - Check
Suspensions - check
Electrical system and battery - check
Headlight - adjustment
Tyres condition and wear - Check
Tyre pressure - check
Vehicle and brake test - road test

* Refer to rules
(°) Refer to predelivery operations

AT 36000 KM

Action

210'

MAIN - 26

AT 72000 KM

ET4 50 Maintenance

Action

Engine oil - replacement
Hub oil level - replacement
Spark plug / electrode gap - check / replacement
Air filter - clean
Oil filter (net filter) - clean
Valve clearance - check
Idle speed (*) - adjustment
Throttle lever - adjustment
Variable speed rollers - check or replacement
Driving belt - replacement
Cylinder ventilation system - check
Odometer gear - greasing
Steering - adjustment
Brake control levers - greasing
Brake pads - check condition and wear
Brake fluid hoses - replacement
Brake fluid level - check
Transmission elements - lubrication
Emergency blockings (°) - Check
Suspensions - check
Electrical system and battery - check
Headlight - adjustment
Tyres condition and wear - Check
Tyre pressure - check
Vehicle and brake test - road test

* Refer to rules
(°) Refer to predelivery operations

10'

Engine oil - level check/ top-up

Brake fluid - change

EVERY 3,000 KM

Action

EVERY 2 YEARS

Action

MAIN - 27

Maintenance ET4 50

Carburettor

- 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. Tank - 9. Starter device - 10. Vacuum valve - 11. Cover - 12. Minimum jet.

Checking the spark advance

The vehicle is provided with a variable spark advance electronic device. Two reference marks for the
timing can be found on the flywheel cover as to find out with more precision the reference mark on the
fan. To check, use a stroboscopic gun Tecnotest 130/P or similar type. Start the engine and let it run
at 1900 revs/min, act on the phase shifter to align the reference mark on the flywheel fan in between
the two reference marks on the casing; at the same time, read the spark advance value on the strobo­scopic gun display. The value should be 10°.
Repeat the above operation with engine running at 5000-6000 revs/min, spark advance should be 26°.

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.

N.B.

WHEN THE INDUCTION CLAMP READS THE SIGNAL CORRECTLY, A READING CAN BE CAR­RIED OUT AT OVER 6000 RPM.

MAIN - 28

ET4 50 Maintenance

RPM LIMITER

Specification Desc./Quantity

1 spark out of 7 8200 Revs/min
1 spark out of 3 8300 Revs/min

Suppression of all sparks 8500 Revs/min

Spark plug

-Disconnect the cap and remove the spark plug.

-Inspect the plug and if the insulator is chipped or
damaged, renew it.

-Measure the spark plug gap with a feeler gauge.
If necessary adjust the gap by bending the outer
electrode.

-Make sure the washer is in good condition.

-Fit the spark plug, screwing it in first by hand and
then tighten it to the prescribed torque with a plug
spanner.

Characteristic

Electrode gap

0.7 ÷ 0.8 mm

Spark plug

Champion RG 4 PHP

MAIN - 29

Maintenance ET4 50

Champion RG 4 HC

Locking torques (N*m)

Spark plug 10 ÷ 15 Nm

Hub oil

Replacement

-Remove the oil filler plug.

-Unscrew the drain plug (A) shown in the figure
and allow the oil to drain out.

-Retighten the drain plug and fill the hub with oil
(about 80 cc).

-Check the level by referring to the min. and max.
notches. Carry out the check after placing the ve­hicle on its stand and removing the cap/dipstick

from the fully tightened position.

Recommended products

AGIP ROTRA 80W-90 rear oil hub

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

Air filter

After removing the lower part of the left-hand side
cover, unscrew the four fixing screws and the two
knobs (which are exposed by overturning the sad­dle and removing the helmet compartment), re­move the filter cover and then pull out the filter
cartridge.
Cleaning:

-Wash the filter with soap and water.

-Dry with a clean cloth without wringing and with
compressed air.

-Soak with a 50% fuel-oil mixture.

-Let the filter cartridge drip and then squeeze it
between the hands without wringing.

CAUTION

MAIN - 30

ET4 50 Maintenance

NEVER RUN THE ENGINE WITHOUT THE AIR FILTER,
THIS WOULD RESULT IN AN EXCESSIVE WEAR OF THE
PISTON AND CYLINDER.

Engine oil

Replacement

-Loosen the oil filler plug.

-Unscrew the gauze strainer drain plug on the fly­wheel side and allow the oil to drain completely.

-Retighten the drain plug and pour in approximate­ly 600-650 cc of oil.

Check

- Put the vehicle on the stand on level ground (cold
engine).

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

- The MAX reference mark corresponds to approx­imately 850 cc of oil in the engine.

- If the oil level is near or below the MIN mark, top
up by adding fresh oil, taking care to never 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

MAIN - 31

Maintenance ET4 50

CO check

- This check can be required when engine opera­tion is irregular or while adjusting the slow running.

- The test must be carried out after carefully wash­ing all carburettor components and making sure
that the air filter is clean and the spark plug is in
good condition.

1) Warm up the engine by riding at a speed of ap­proximately 50 km/h for ~ 5 minutes. This will allow
the automatic starting device to cut out its circuit.

2) Switch off the engine for the minimum time re­quired to perform steps 3) and 4).

3) Fit an extension tube ~ 50 cm in length to the
exhaust gas outlet on the silencer.

4) Take special care in ensuring the seal between
the silencer and the tube. Insert the exhaust gas
analyser probe into the tube.

5) Connect the multimeter thermometer to the
sump using an oil filler plug specially prepared for
the insertion of the probe.

6) Start the engine and, before proceeding to tune
up the idle speed, ensure that the oil temperature
is 70-80° C.

7) Allow the idle speed to stabilize for about a mi­nute.

8) Without opening the throttle and using the
specially designed flow screw, adjust the speed of
the engine to 1,650 ± 50 rpm.

9) Adjust the flow screw until the «CO» percentage
is 3.8 ± 0.7 percent.

10) Slowly rotate the throttle twist grip until the
engine reaches a speed of 4,000 rpm, then close
the throttle again. Check that the idle speed is the
same as specified above. If not, repeat the proce­dure from step 3).

Specific tooling

020332Y Digital rev counter

MAIN - 32

ET4 50 Maintenance

494929Y Exhaust fumes analyser
020331Y Digital multimeter

MAIN - 33

INDEX OF TOPICS

TROUBLESHOOTING TROUBL

ET4 50 Troubleshooting

Engine

Poor performance

POOR PERFORMANCE

Possible Cause Operation

Air filter clogged or dirty Disassemble, wash sponge with water and shampoo and im-

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

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

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

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

Timing failure or timing system parts worn Reset timing phase or replace any worn parts (refer to 4-stroke

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

merse in a mixture of 50% petrol and Selenia Air Filter oil. Let

it drip. Wring out without squeezing it and then refit

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

sary

aged parts and lubricate the driven pulley moveable guide with

Montblanc Molybdenum Grease

50 cc engine manual)

Rear wheel spins at idle

REAR WHEEL

Possible Cause

Idling rpms 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

Operation

Starting difficulties

STARTING PROBLEMS

Possible Cause

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

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

- Engine flooded. Start up keeping the throttle fully open alternating approximate­ly five seconds of turning it with five seconds still. 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

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

Operation

trode gap

itself

if necessary.

TROUBL - 35

Troubleshooting ET4 50

Possible Cause Operation

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

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

Starting rpm too low. Starter motor faulty. Check starting motor.

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

necessary

Engine tends to cut-off at full throttle

ENGINE TENDS TO CUT OUT AT FULL THROTTLE

Possible Cause Operation

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

Water or condensate in the carburettor tank Remove the tank, wash with solvent and dry with compressed

air or empty the tank through the appropriate bleed screw

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

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 tank (the float must be parallel

to the upper cover contact plane, that is the throttle valve mem-

Fuel supply pipes choked or clogged Restore the adequate fuel supply

Tank breather hole obstructed Restore the proper tank aeration

Level in tank too low Restore the correct level in the tank (the float must be parallel

to the upper cover contact plane, that is the throttle valve mem-

pressed air

wheel correct keying

brane cover)

brane cover)

Engine tends to cut-off at idle

ENGINE TENDS TO STOP WHEN IDLING

Possible Cause

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

Level in tank too high Restore the correct level in the tank (the float must be parallel

Automatic choke stays activated Check that the piston slides freely and that fuel is supplied to

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

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

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

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

High fuel consumption

Operation

valve

to the upper cover contact plane, that is the throttle valve mem-

brane cover)

the automatic choke. Renew if necessary

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.

C.O.

check the plug gap

TROUBL - 36

EXCESSIVE FUEL CONSUMPTION

Possible Cause

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 (Se-

Operation

ET4 50 Troubleshooting

Possible Cause Operation

lenia Air Filter Oil), then hand dry without squeezing, allow to

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

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

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 contact surface with the casing is mainly in the
centre with equivalent characteristics on the three masses.

Check that the clutch casing is not scored or worn in an anom-

drip dry and then reassemble.

fixed in their fittings

alous way

Insufficient braking

Possible Cause

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

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

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

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

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

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

Return spring broken Replace spring.

Shoe control bolt not lubricated Lubricate with Z2 grease.

Brakes overheating

Possible Cause

Defective sliding of pistons 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

INEFFICIENT BRAKING

Operation

drum wear conditions.

no flexible movement of the brake lever).

wheel correctly fitted and the concentricity of the rear drum;

check the brake disc screws are locked

trol lever

the pump

BRAKES OVERHEATING

Operation

wheel correctly fitted and the concentricity of the rear drum;

check the brake disc screws are locked

Electrical system

TROUBL - 37

Troubleshooting ET4 50

Battery

BATTERY

Possible Cause Operation

This device requires the most assiduous surveillance and the

most diligent maintenance.

This device requires the most assiduous surveillance and the

most diligent maintenance. If the vehicle is not used for some
time (1 month or more) the battery needs to be recharged pe­riodically. The battery tends to exhaust its power supply in five
to six 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 EQUIPMENT FAILURE

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

Possible Cause

Steering hardening Check the tightening of the top and bottom ring nuts. If irregu-

Excessive steering play

EXCESSIVE STEERING CLEARANCE

Possible Cause

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

Noisy suspension

STEERING HARDENING

Operation

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

tened.

Operation

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.

TROUBL - 38

SUSPENSION NOISY

Possible Cause

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

sorber works properly and the ball bearings are good condition.
In conclusion, check the tightening torque of the wheel hub, the
brake calliper, the shock absorber disk in the attachment to the

Check that the swinging arm connecting the engine to the

chassis and the rear shock absorber work properly

Operation

hub and the steering tube.

ET4 50 Troubleshooting

Suspension oil leakage

OIL LEAKAGE FROM SUSPENSION

Possible Cause Operation

Oil leakage from suspension Replace the damper.

TROUBL - 39

INDEX OF TOPICS

ELECTRICAL SYSTEM ELE SYS

ET4 50 Electrical system

ELECTRICAL EQUIPMENT

Specification

1 Horn
2 Headlight bulb 12V-35/35W
3 Parking light bulb 12V-5W
4 Key switch
5 Front brake stop button
6 Light switch
7 Turn indicator switch
8 Horn button
9 Light switch
10 Starter button
11 Speedometer with fuel gauge and warning lights -

12V-1.2W reserve fuel warning light bulb, 2 x 12V-2W

turn indicator warning light bulbs, 12V-1.2W high beam

warning light bulb, 12V-1.2W instrument lighting bulb,

12V-1.2W lights-on warning light bulb.
12 Rear stop light switch
13 Starter remote control
14 Voltage regulator
15 Battery 12V - 9Ah
16 Rear turn indicator bulbs Two, 12V-10W, spherical
17 Front direction indicator lights N° 2, 12V-10W, spherical
18 Brake light button on rear brake 12V-21/5W
19 Magneto flywheel
20 Pick - up
21 Automatic starter
22 Starter motor
23 Fuel level sending unit
24 Fuse 10 A
25 Headlight assembly
26 Rear light assembly
27 Electronic ignition device

Desc./Quantity

Wiring colour chart:

ELE SYS - 41

Electrical system ET4 50

B=White - Bl=Blue - G=Yellow - M=Brown - N=Black - BV=White-Green - GN=Yellow-Black - Gr=Grey

- Rs=Pink - R=Red - Vi=Purple - V=Green - VN=Green-Black - BN=White-Black - BBl=White-Blue ­GV=Yellow-Green - Ar=Orange - GrBl=Grey-Blue - GrN=Grey-Black - BR=White-Red - RN=Red-Black

- BlN=Blue-Black.

CAUTION

SHOULD ANY INTERVENTIONS TO THE ELECTRIC SYSTEM BE REQUIRED, MAKE SURE THAT
THE LEADS TO THE ELECTRONIC IGNITION DEVICE ARE PROPERLY CONNECTED ACCORD­ING TO POLARITY AND TO THE LEAD COLOURS.

Conceptual diagrams

Ignition

IGNITION SECTION

Specification

1 Electronic ignition device
2 Key switch contacts
3 Voltage regulator
4 Magneto flywheel
5 Pick - up
6 Main fuse 10A
7 Battery 12V - 9Ah

ELE SYS - 42

Desc./Quantity

ET4 50 Electrical system

Headlights and automatic starter section

LIGHTS

Specification

1 Voltage regulator
2 Main fuse 10A
3 Magneto flywheel
4 Key switch contacts
5 Headlight bulb 12V-35/35W
6 High-beam warning light 12V - 1.2W
7 Parking light bulb 12V- 5W
8 2 Instrument lighting bulbs 12V- 1,2W
9 1 Instrument panel lighting bulb 12V- 2W
10 Lights-on warning, 1 light bulb 12V-1,2W
11 Rear light bulb, 1 light bulb 12V-5/21W
12 Electronic ignition device
13 Automatic starter
14 Light switch
15 Light switch
16 Battery 12V - 9Ah

Desc./Quantity

ELE SYS - 43

Electrical system ET4 50

Battery recharge and starting

BATTERY RECHARGE AND STARTING

Specification

1 Magneto flywheel
2 Starter motor
3 Main fuse 10A
4 Battery 12V - 9Ah
5 Key switch contacts
6 Voltage regulator
7 Electronic ignition device
8 Starter remote control
9 Starter button
10 Front and rear brake light button

Desc./Quantity

ELE SYS - 44

ET4 50 Electrical system

Level indicators and enable signals section

SAFETY SWITCHES

Specification

1 Voltage regulator
2 Fuel gauge
3 Fuel level sending unit
4 Low fuel warning light
5 Front and rear brake light button
6 Horn 12V
7 Horn button
8 Brake light filament 12V-21W

Desc./Quantity

ELE SYS - 45

Electrical system ET4 50

Turn signal lights

TURN SIGNAL LIGHTS

Specification

1 Turn indicator switch
2 Voltage regulator
3 4 Turn indicator bulbs 12V-10W
4 Two (2) turn signal warning light bulbs 12V - 2W

Desc./Quantity

ELE SYS - 46

ET4 50 Electrical system

Instruments and warning lights control board

WARNING LIGHTS AND GAUGES PANEL

Specification

1 Left turn indicator warning light 12V - 2W
2 High-beam warning light 12V - 1.2W
3 Fuel Level indicator
4 Instrument panel lighting bulb 12V-1,2W
5 Headlight warning light 12V 1.2W
6 Reserve fuel light 12V-1,2W
7 Right turn indicator warning light 12V - 2W
8 Dashboard light bulbs 12V-2W
9 Available warning light

Desc./Quantity

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.

ELE SYS - 47

Electrical system ET4 50

If faulty or failed operation persists, conduct the
following checks on the generator and on the sta­tor components:
After a visual inspection of the electrical connec­tions, it is possible to perform measurements on
the stator winding and pick-up (see table), using
the specific multimeter.
If, during the checks on the charge coil and the
pick-up, anomalies are found, replace the stator
and other faulty parts.
Disconnect the connector on the flywheel housing
and measure the resistance between each of the
two contacts and the earth.

Specific tooling

020331Y Digital multimeter

PICK-UP CHECK

Specification

1 1) Brown cable and earth ~ 170 Ω

Desc./Quantity

STATOR WINDING CHECK

Specification

1 1) Black cable and earth ~ 1 Ω

Desc./Quantity

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 irreparably dam­aged.

ELE SYS - 48

ET4 50 Electrical system

Voltage regulator check

The malfunctioning of the voltage regulator might cause the following problems depending on the type
of fault:

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

2) The lighting and electrical starter system do not work (regulator interrupted).

3) Battery fails to charge

4) Turn indicators failure
The regulator is provided with earth supplied from the electrical equipment, therefore the regulator body
does not supply earth to the internal circuits. Check the insulation between each terminal of the regulator
and its body, using the specific tester.

1) BURSTING LIGHT BULBS
Replace the voltage regulator as this is definitely
faulty.

2) HEADLIGHTS AND CHOKE NOT-OPERA­TIONAL
In order to leave the AC free from absorptions, so
to carry out voltage checks, please proceed as fol­lows. Remove the handlebar covers. Detach the
connections from the headlight and the 5 PIN con­nector from the dashboard. Remove the taillight
bulb. Remove the automatic choke connector from
the system.
Access the voltage regulator, start the engine and
let it run at idle.
Insert the positive terminal from the tester (setting
the tester on AC mode) on terminal no. 1 (yellow­black wire) and the negative terminal on terminal
no. 2 (black wire); check for voltage (see figure).
If voltage is present, check the wiring from the
headlight to the voltage regulator, and the opera­tion of the light switch.
If no voltage is found, put the negative terminal to
earth; if this provides voltage readings, check the
earth wire (terminal no. 2) on the regulator (black
wire); otherwise, replace the regulator as certainly
faulty.

ELE SYS - 49

Electrical system ET4 50

As a last test it is possible to check the output volt­age from the stator:

-Detach the regulator connector and interpose the
tester in AC mode, between the Gray-Blue wire (4)
and earth (see figure).

-The voltage output at 2,000 rpm must be approx.
25 - 35V
If this test also gives no voltage, replace the reg­ulator as certainly faulty.

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 DOES NOT RECHARGE
The fault in the DC section of the voltage regulator
may cause, depending on the type of failure, the
following faults:

a) Bursting of protection fuse due to exces­sively high voltage (regulator short-circuited)
and resulting in the battery not recharging.
b) Battery not recharging (regulator circuit in­terrupted).
Interventions

a) Bursting of protection fuse (regulator short­circuited).
Check the wiring running from the fuse to the ig­nition key-switch is not damaged, as this may cre­ate a short-circuit with earth (thus excluding
possible regulator failures); if the protection fuse
bursts only after the ignition key-switch is turned
to "ON", and with the regulator connector detach­ed, it is then necessary to check the wirings and
systems downstream the key-switch are not short­circuited with earth.

ELE SYS - 50

ET4 50 Electrical system

Proceed by measuring the resistance between
contacts 3 (White) and 2 (Black) from the voltage
regulator (with the connector detached).
If the reading differs excessively from the figures
shown, replace the regulator as short-circuited.
b) Battery not recharging (regulator circuit inter­rupted).
To check for the presence of faults on the recharg­ing section of the voltage regulator, it is necessary
to initially operate on the battery, using two testers
(one for voltages and one for currents), as shown
in the second figure, and follow the operations giv­en below:
Start the engine (connecting, temporarily, the red
wire to the positive terminal of the battery, so to
avoid damaging the instrument measuring the cur­rent).
Check the voltage at idle is at least 13V (charged
battery) and the recharge current is 1.5 - 2A with
the lighting system and the choke device exclu­ded, as described in the chapter "CHECKING THE
VOLTAGE REGULATOR".
As the engine speed increases, so do the recharge
current and voltage, and at speeds above 4,000
rpm, a recharging current of approx. 4.5A must be
observed; reactivating the lighting system and
choke device, and operating the stop light and
horn, current values of ≥ 5A may be found, with
voltage readings of 14 - 14.5V (regulator threshold
voltage).

If the readings do not match the above figures,
replace the regulator; otherwise check wiring
and connections.

Electric characteristic

Resistance of voltage regulator

~ 8 MΩ

ELE SYS - 51

Electrical system ET4 50

Turn signals system check

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

- Disconnect the regulator connection and insert
the multimeter probes between the white cable (3)
and the black one (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 white cable and
the earth; if there is no voltage even after this op­eration, check the wiring and the contacts of the
key switch and the battery. If voltage in the battery
is detected (black cable), check the regulator earth
wiring.

- If the above tests have positive results, jump the
contacts 5 (blue/black) and 3 (white) on the con­nector, set the key switch to ON and the turn
indicator switch left and right to see when the lights
are steadily on (as they are powered directly from
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

ELE SYS - 52

ET4 50 Electrical system

Sealed battery

INSTRUCTIONS FOR REFRESHING THE
STOCK CHARGE OF AN OPEN CIRCUIT

1) Voltage check

Before installing the battery on the vehicle, check
the open circuit voltage with a normal tester.

- If the voltage exceeds 12.60 V, the battery may
be installed without any renewal recharge.

- If voltage is below 12.60 V, a renewal recharge
is required as explained in 2).

2) Constant voltage battery charge mode

-Constant voltage equal to 14.40÷14.70V

-Initial charge voltage equal to 0.3÷0.5 for nominal
capacity

-Duration of the charge: 10 to 12 h recommended
Minimum 6 h
Maximum 24 h

3) Constant current battery charge mode

-Charge current equal to 1/10 of the nominal ca­pacity of the battery

-Duration of the charge: 5 h

WARNING

-WHEN THE BATTERY IS REALLY FLAT (WELL BELOW

12.6V) IT MIGHT BE THAT 5 HOURS OF RECHARGING ARE
NOT ENOUGH TO ACHIEVE OPTIMAL PERFORMANCE.
IN THESE CONDITIONS IT IS HOWEVER ESSENTIAL NOT
TO EXCEED EIGHT HOURS OF CONTINUOUS RECHARG­ING SO AS NOT TO DAMAGE THE BATTERY ITSELF.

1 Hold the vertical tube
2 Look at the level
3 The float must be freed

Dry-charge battery

The battery is an electrical device which requires careful monitoring and diligent maintenance. The
maintenance rules are:

1) Check the level of the electrolyte

The electrolyte level must be checked frequently and must reach the upper level. Only use distilled
water, to restore this level.
If it is necessary to add water too frequently, check the vehicle's electrical system: the battery works
overcharged and is subject to quick wear.

ELE SYS - 53

Electrical system ET4 50

2)Load status check

After restoring the electrolyte level, check its density using an appropriate densitometer (see the figure).
When the battery is charged, you should detect a density of 30 to 32 Bé corresponding to a specific
weight of 1.26 to 1.28 at a temperature of no lower than 15° C.
A density reading of less than 20° Bé indicates that the battery is completely flat and it must therefore
be recharged.
After charging the battery, check each element electrolyte level and density. If the scooter is not used
for a given time (1 month or more) it will be necessary to periodically recharge the battery.
The battery runs down completely in the course of three months.
If it is necessary to refit the battery in the vehicle, be careful not to reverse the connections, remembering
that the earth wire (black) marked (-) must be connected to the - negative terminal while the other two
red wires marked (+) must be connected to the terminal marked with the + positive sign.
Regular bench charging must be carried out with the specific battery charger, (single) or (multiple),
setting the battery charger selector to the type of battery to be recharged. Connections to the power
supply source must be implemented by connecting the corresponding poles (+ to+ and - to -).

4) Cleaning the battery

The battery should always be kept clean, especially on its top side, and the terminals should be coated
with Vaseline.

WARNING

- Before recharging the battery, remove the plugs of each cell. Keep the battery away from naked flames
or sparks when charging.
Remove the battery from the vehicle removing the negative clamp first.

CAUTION

NEVER USE FUSES WITH A CAPACITY HIGHER THAN THAT RECOMMENDED.
USING A FUSE OF UNSUITABLE RATING MAY SERIOUSLY DAMAGE THE VEHICLE OR EVEN
CAUSE A FIRE.

CAUTION

DRINKING WATER CONTAINS MINERALS THAT CAN BE EXTREMELY HARMFUL TO THE BAT­TERY: USE DISTILLED WATER ONLY.

CAUTION

TO ENSURE MAXIMUM PERFORMANCE THE BATTERY MUST BE CHARGED BEFORE USE.
INADEQUATE CHARGING OF THE BATTERY WITH A LOW ELECTROLYTE LEVEL BEFORE IT
IS FIRST USED SHORTENS THE LIFE OF THE BATTERY.

Specific tooling

020333Y Single battery charger
020334Y Multiple battery charger

1)- Remove the short closed tube and the caps, then pour sulphuric acid into the cells using the type
specified for batteries, with a specific gravity of 1.26, corresponding to 30° Bé, at a minimum temperature
of 15°C until the upper level is reached.

2) - Leave to rest for at least 2 hours; then, restore the level with sulphuric acid.

ELE SYS - 54

ET4 50 Electrical system

3)- Within the following 24 hours, recharge with the specific battery charger (single) or (multiple) at a
density of about 1/10 of the battery nominal capacity and until the acid density is about 1.27, corre­sponding to 31º Bé, and these values are stabilised.

4) - Once the charge is over, level the acid (by adding distilled water). Close and clean carefully.

5)- Once the above operations have been performed, install the battery in the vehicle ensuring the
connections between the wiring and the battery terminals are correct.

WARNING

- ONCE THE BATTERY HAS BEEN INSTALLED IN THE VEHICLE IT IS NECESSARY TO REPLACE
THE SHORT TUBE (WITH CLOSED END) NEAR THE + POSITIVE TERMINAL WITH THE CORRE­SPONDING LONG TUBE (WITH OPEN END), THAT YOU FIND FITTED TO THE VEHICLE, TO
ENSURE THAT THE GASES THAT FORM CAN ESCAPE PROPERLY.

Specific tooling

020333Y Single battery charger
020334Y Multiple battery charger

WARNING

- Battery electrolyte is toxic and it may cause serious burns. It contains sulphuric acid. Avoid contact
with eyes, skin and clothing. In case of contact with eyes or skin, flush abundantly with water for about
15 minutes and seek immediate medical attention.
In the event of accidental ingestion of the fluid, immediately drink large quantities of water or milk. Follow
with milk of magnesia, beaten egg or vegetable oil. Seek immediate medical attention
Batteries produce explosive gases; keep clear of free flames, sparks or cigarettes; ventilate the area
when recharging the battery indoors.
Always protect your eyes when working close to batteries.

Keep out of the reach of children.

ELE SYS - 55

INDEX OF TOPICS

ENGINE FROM VEHICLE ENG VE

ET4 50 Engine from vehicle

Exhaust assy. Removal

- Remove the 2 fixing nuts from the manifold to the
head

- Unscrew the 2 screws fixing the muffler to the
housing; 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

Disassembling engine from frame

-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.

ENG VE - 57

INDEX OF TOPICS

ENGINE ENG

ET4 50 Engine

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 indicated
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.

ENG - 59

Engine ET4 50

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 DRIVE

PULLEY MOUNTED.

Specific tooling

020565Y Flywheel lock calliper spanner

ENG - 60

ET4 50 Engine

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

ENG - 61

Engine ET4 50

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 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 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.

ENG - 62

ET4 50 Engine

Removing the driven half-pulley bearing

- Remove the roller bearing with the special ex­tractor 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 un­usual wear.

- Measure the external diameter of the pulley bush­ing.

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

ENG - 63

Engine ET4 50

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 tone wheel
revolving ring

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 gr. 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 tone wheel revolving ring

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

ENG - 64

ET4 50 Engine

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.

ENG - 65

Engine ET4 50

- 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

ENG - 66

ET4 50 Engine

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

- Measure outside diameter «B» of the pulley slid­ing bushing shown in the figure.

CAUTION
DO NOT LUBRICATE OR CLEAN THE BUSHING.

Characteristic

Driving pulley / Maximum diameter:

ENG - 67

Engine ET4 50

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

ENG - 68

ET4 50 Engine

Refitting the transmission cover

- Check the following for wear: toothed section,
toothed section shaft, cover seat bushing, pinion
shaft and it 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

ENG - 69

Engine ET4 50

Removing the hub cover

- Drain the rear hub oil

- Remove driven pulley

- Remove the rear brake shoes

- Remove the 5 screws fixing the cover to the
crankcase

- Remove the cover with the wheel axle and pull it
out

- Remove the intermediate gear with the appropri­ate shim washers

Removing the wheel axle bearings

- Remove the oil seal and the seeger ring.

- Fix the hub cover properly to avoid damaging the
sealing surface with the housing

- Remove the wheel axle bearing using the specific
tool

Specific tooling

020363Y 20 mm guide
020376Y Adaptor handle
020477Y Adaptor 37 mm

ENG - 70

ET4 50 Engine

Removing the driven pulley shaft bearing

- Remove the seeger ring

- Heat the engine crankcase but do not direct the
hot air towards the bearing

- Extract the driven pulley shaft together with the
bearing with a few mallet blows

- Remove the bearing off the driven pulley shaft
using the specific tool and a press

N.B.
USE THE SPECIFIC TOOL ON THE SIDE WITH THE SMALL-

ER INTERNAL DIAMETER

Specific tooling

020452Y Tube for removing and refitting the
driven pulley shaft

ENG - 71

Engine ET4 50

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 com­ponents.

- 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.

Refitting the wheel axle bearing

- Support the hub cover on a wooden surface

- Heat up the hub cover using the thermal gun.

- Preassemble the bearing on the specific punch
using grease and then insert the bearing in its
seating

- Refit the seeger ring and the oil seal using the 42
x 47 mm adaptor

N.B.
POSITION THE OIL SEAL WITH THE SEALING LIP FACING

THE HUB INTERNAL SIDE

Specific tooling

020150Y Air heater support
020151Y Air heater
020376Y Adaptor handle

ENG - 72

ET4 50 Engine

020363Y 20 mm guide
020359Y 42x47-mm adaptor

Refitting the hub bearings

- Remove the wheel axle on the cover and pay at­tention not to damage the sealing lip of the oil seal

- Apply a thin layer of grease on the two shim
washers of the intermediate gear and fit one on the
cap so that it does not interfere with the wheel axle
gear when placing the transmission shaft

Refitting the ub cover

- Apply product recommended for surfaces on the
hub cap and refit cap on the crankcase

- Fit the 5 screws and tighten them to the specified
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.

Recommended products

Loctite 510 Liquid sealant

ENG - 73

Engine ET4 50

Gasket

Locking torques (N*m)

hub cap screws 24 - 26

Flywheel cover

Cooling hood

- Remove the manifold and the carburettor undo­ing 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 re­verse 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.

ENG - 74

ET4 50 Engine

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.

Refitting the stator

- Refit the stator and flywheel carrying out the re­moval 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

ENG - 75

Engine ET4 50

Removing the starter motor

- Unscrew the screw on the power positive contact
and disconnect the cable

- Unscrew the 2 screws fixing the starter motor to
the crankcase and recover the power wiring.

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

ENG - 76

ET4 50 Engine

Inspecting the flywheel components

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

- Check that the flywheel riveted joints are correctly
tightened.

- 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.

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 ade­quately.

ENG - 77

Engine ET4 50

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

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 motor screws 11 ÷ 13

Cylinder assy. and timing system

ENG - 78

ET4 50 Engine

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

Removal
Removing the driving pulley

ENG - 79

Engine ET4 50

Removing the cam shaft

- Remove the bearing clamping screw indicated in
the figure.

- 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

- Pull out the rocking lever bolt operating on the
flywheel hole and remove the rocking levers at the
same time.

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

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

ENG - 80

ET4 50 Engine

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 element
shown in the figure, remove the cotters, the plates
and the spring between the valves.

- Remove the oil seals with the appropriate tool.

- Remove the lower spring supports.

Specific tooling

020431Y Valve oil seal extractor

ENG - 81

Engine ET4 50

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

ENG - 82

ET4 50 Engine

Inspecting the wrist pin

- Measure the outer diameter of the gudgeon pin.

Characteristic

Standard diameter gudgeon pin

13 -0-0.004mm

Minimum admissible diameter pin

12.990 mm

Inspecting the piston

- Calculate the piston pin coupling clearance.

Fitting clearance

Pin coupling clearance 13 +0.010+0.005mm 0.005 ÷

0.014 mm

- Measure the outside diameter of the piston, perpendicular to the gudgeon pin axis.

- Carry out the measurement at 27 from the piston crown as shown in the figure.

- Carefully clean the sealing rings housings with the aid of an old piston ring.

- Measure the coupling clearance between the sealing rings and the piston grooves using a thickness
gauge, as shown in the figure.

- If the clearances detected exceed the limits specified in the table, the piston and the piston rings should
be replaced.

PISTON

Name

Top piston ring 0.030 ÷ 0.065 mm 0.080 mm

Middle piston ring 0.020 ÷ 0.055 mm 0.070 mm

oil scraper 0.040 ÷ 0.160 mm 0.20 mm

Description Dimensions Initials Quantity

ENG - 83

Engine ET4 50

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

- The cylinder rectifying operation should be car­ried out with a surfacing that respects the original
angle. at 120° crossed.

- The cylinder surface roughness should be of
R.A.= 0.30 ÷ 0.50.

- This is indispensable for a good seating of the
sealing rings, which in turn minimises oil consump­tion and guarantees optimum performance.

- The pistons are oversized due to cylinder rectifi­cation and are subdivided into two categories 1st
and 2nd with 0.2-0.4mm oversize. They are also
classified into 4 categories A-A, B-B, C-C, D-D.

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.

ENG - 84

ET4 50 Engine

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.

SEALING RINGS

Name Description Dimensions Initials Quantity

Top piston ring 0.08 ÷ 0.20 mm 0.35 mm

Middle piston ring 0.05 ÷ 0.20 mm 0.30 mm

oil scraper 0.20 ÷ 0.70 mm 0.80 mm

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

- 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.

ENG - 85

Engine ET4 50

Choosing the gasket

This engine is manufactured with two different head gasket solutions:

- Fibre gasket drw. 969244 0.95 mm thick.

- Steel gasket drw. 969393 0.3 mm thick.
In order to guarantee an adequate compression ratio, the gaskets match cylinders with different heights:

- Fibre gaskets with cylinder 56.45 mm high

- Fibre gaskets with cylinder 57.15 mm high

In order to carry out the revision both gaskets should be present on the spare parts.
All pin-piston-cylinder units supplied with the spare parts present cylinders 57.15 mm high

- Provisionally fit the piston into the cylinder, without any base gasket.

- Fit a dial gauge on the specific tool, then rest both on a stop surface.

- Zero set the dial gauge on the stop surface. Keeping the zero position, assemble the tool on the cylinder
and lock it with 2 nuts as shown in the figure.

- Rotate the crankshaft until TDC (the inverted point of the dial gauge rotation)

- Measure piston protrusion compared with the head plane and determine the gasket thickness to be
used according to the table below. By correctly identifying the cylinder base gasket thickness, an ade­quate compression ratio is maintained.

- Remove the specific tool and the cylinder.

Characteristic

Standard compression ratio

C.R. 11.5 ÷ 12 ÷ 1

CYLINDER BASE GASKET THICKNESS

Specification

Cylinder height 56.45 ± 0.05

Head gasket thickness (fibre) 0.95 ± 0.06

Measure detected 0.9 ± 0.05

Base gasket thickness 0.4

Measure detected 1 ± 0.05

Base gasket thickness 0.5

Desc./Quantity

ENG - 86

CYLINDER BASE GASKET THICKNESS

Specification

Cylinder height 57.15 ± 0.05

Head gasket thickness (steel) 0.3 ± 0.05

Measure detected 0.20 ± 0.05

Base gasket thickness 0.4

Measure detected 0.30 ± 0.05

Base gasket thickness 0.5

Desc./Quantity

ET4 50 Engine

N.B.

MEASUREMENT "A" TO BE TAKEN IS A VALUE OF PISTON RE-ENTRY, IT INDICATES BY HOW
MUCH THE PLANE FORMED BY THE PISTON CROWN FALLS BELOW THE PLANE FORMED BY
THE TOP OF THE CYLINDER. THE FURTHER THE PISTON GETS INSIDE THE CYLINDER, THE
THINNER THE HEAD GASKET TO BE APPLIED SHOULD BE (TO RECOVER THE COMPRESSION
RATIO) AND VICE VERSA.

Characteristic

Shimming system to control the compression ratio

CR: 11.1 ÷ 12.9

PISTON PROTRUSION CHECK

Name

shimming_1 0.05 ÷ 0.25 0.35
shimming_2 0.25 ÷ 0.40 0.25

Measure A Thickness

ENG - 87

Engine ET4 50

Refitting 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.

SEALING RINGS

Name

Top piston

ring

Middle pis-

ton ring

oil scraper 0.20 ÷

DescriptionDimensionsInitials Quantity

0.08 ÷

0.20 mm

0.05 ÷

0.20 mm

0.70 mm

0.35 mm

0.30 mm

0.80 mm

ENG - 88

ET4 50 Engine

- 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.

- Offset the ring gaps by 120° to each other 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.

Refitting the cylinder

- Fit the base gasket of the chosen thickness, pre­viously determined.

- 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.

ENG - 89

Engine ET4 50

The procedure is different from that indicated in the vehicle manuals:
Head nuts tightening (only for stud bolts replacement) 6÷7 N*m +90° + 90° + 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.

Characteristic

Maximum admitted unevenness: Head check

0.05 mm

HEAD CHECK

Specification

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

Desc./Quantity

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.

ENG - 90

ET4 50 Engine

- 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.

Inspecting the valve sealings

- Measure the width of the sealing surface on the
valve seats.

Characteristic

Sealing surface width: Intake

1.5 mm

Sealing surface width: Drainage

1.6 mm

- Insert the valves into the cylinder head.

- Test the 2 valves alternatively.

- 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 valve housings

- Remove any carbon formation from the valve
guides.

- Measure the inside diameter of each valve guide.

- Take the measurement at three different heights
in the rocker arm push direction.

Characteristic

Discharge guide: Standard diameter

5 +0+0.012mm

Discharge guide: Wear limit

5.022 mm

Intake guide: Standard diameter

ENG - 91

Engine ET4 50

5 +0+0.012mm

Intake guide: Wear limit

5.022 mm

- If the width of the impression on the valve seat or the diameter of the valve guide exceed the specified
limits, replace the cylinder head.

- Check width of the impression on the valve seat «V»

Characteristic

Wear limits:

Max. 1.6 mm.

Inspecting the valves

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

- Calculate the clearance between the valve and
the valve guide.

Characteristic

Minimum diameter allowed: Intake

4.970 mm

Minimum admissible diameter drainage

4.960 mm

Fitting clearance

Standard clearance: Intake 0.015 ÷ 0.042 mm
Standard clearance: drainage 0.025 ÷ 0.052 mm

- Check that there are no signs of wear on the
contact surface with the articulated register termi­nal.

- If the sealing surface on the valves is wider than
the specified limit, damaged in one or more points
or curved, replace the valve with a new one.

Characteristic

Valve standard length: Intake

70.1 mm

Valve standard length: drainage

69.2 mm

Fitting clearance

Max. clearance allowed: Intake 0.052 mm Max.
clearance allowed: drainage 0.062 mm

- If the checks above give no failures, you can use the same valves. For best sealing results, it is
advisable to grind the valves. Grind the valves gently with a fine-grained lapping compound. During

ENG - 92

ET4 50 Engine

grinding, keep the cylinder head in a horizontal position. This will prevent the lapping compound resi­dues from penetrating between the valve stem/guide coupling.

CAUTION

TO AVOID SCORING THE CONTACT 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.

Inspecting the springs and half-cones

- Check that the upper spring caps and the cotter
halves show no signs of abnormal wear.

Refitting the valves

- Lubricate the valve guides with graphite grease.

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

- Use the punch to fit the 2 sealing rings one at a
time.

Specific tooling

020306Y Punch for assembling valve seal
rings

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

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

ENG - 93

Engine ET4 50

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

- 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 - Intake:

25.935 mm

Standard height - Discharge:

25.935 mm

Fitting clearance

Maximum admissible axial clearance 0.5 mm

- Check there are no signs of scoring or wear on
the rocking lever bolt.

- Measure the diameter «A».

- Measure the internal diameter of each rocking
lever. level «B».
Check there are no signs of wear on the pad from
contact with the cam and on the jointed adjustment
plate.

- In case of anomalies, replace the damaged com­ponents.

Characteristic

ENG - 94

ET4 50 Engine

Minimum admissible diameter

Ø 10.970 mm

Maximum diameter allowed:

Ø 11.030 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.

- 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

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

- Loosen the rocking lever registers.

- Fit the pin, the intake rocking lever and the 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 the limit screw for the pin and the camshaft
with the washer indicated in the figure and tighten
it to the prescribed torque.

Locking torques (N*m)

Rocking lever axle and camshaft bearing
screw 3 ÷ 4 Nm

ENG - 95

Engine ET4 50

- 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

Refitting the timing chain

- Insert the timing chain pads in their correspond­ing 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 cam­shaft control pulley and make the reference notch
coincide with the point on the head.

- Fit the pulley on the camshaft.

- Fit the belleville washer so that the outer rim
touches the pulley.

ENG - 96

ET4 50 Engine

- 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)

Camshaft pulley screw 12 ÷ 14 Head cover screw 8 ÷ 10 Nm

- Set the tensioner cursor in the rest position.

- Fit the chain tensioner on the cylinder, using a new gasket, and tight the two screws to the prescribed
torque.

- Insert the spring with the central screw and tighten it to the prescribed torque.

- Fit the spark plug.

Characteristic

Recommended spark plug

NGK CR 9EB - CHAMPION RG 4HC

Electric characteristic

Electrode gap

0.7 ÷ 0.8 mm

Locking torques (N*m)

Timing chain tensioner screw 8 ÷ 10 Nm Timing chain tensioner central screw 5 - 6 Ignition spark
plug 10 ÷ 15 Nm

ENG - 97

Engine ET4 50

Refitting the rocker-arms cover

- Carry out the removal procedure but in reverse
order and tighten the four fixing screws to the
specified torque.

N.B.
FIT A NEW O-RING ON THE TAPPET COVER.

Locking torques (N*m)

Timing chain tensioner screws 8 ÷ 10 Nm

Refitting the intake manifold

-Fit the cover sealing gaskets on the head.

-Fit the 2 covers.

- Fit the inlet manifold and do up the 2 screws to
the specified torque.

-Fit the carburettor on the inlet manifold and lock
the clamp.

-Fit the secondary air pipe and fix it with the ap­propriate clamp.

N.B.
FIT THE CARBURETTOR THROUGH THE SUPPLEMENT

ON THE MANIFOLD.

Locking torques (N*m)

Inlet manifold screw 7 ÷ 9 Nm

Crankcase - crankshaft

- First remove the following units:
Driving pulley Driven pulley
Final reduction greasing
Oil pump Flywheel with stator
Cylinder-piston-head unit
Starter motor with cables.

See also

Removing the starter motor
Removing the driven pulley
Removing the stator
Removal
Removing the cylinder - piston assy.
Removing the driving pulley

ENG - 98

ET4 50 Engine

Splitting the crankcase halves

- Remove the ten crankshaft coupling screws.

-Separate the crankcase halves keeping the half
casing driving shaft engaged on the transmission
side.

- Remove the crankshaft.

CAUTION
IF YOU FAIL TO DO THIS, THE CRANKSHAFT MIGHT AC-

CIDENTALLY FALL.

- Remove the oil guard on the flywheel side.

CAUTION

THE CENTRIFUGAL OIL FILTER IS IN THE FLYWHEEL AXLE SHAFT. CONSEQUENTLY, DO NOT
WASH WITH SOLVENTS OR BLOW COMPRESSED AIR SO THAT NO IMPURITIES LEAK OUT. A
CENTRIFUGAL OIL FILTER'S LIFE IS THE SAME AS THE ENGINE'S AND IS MAINTENANCE
FREE.

- Check the axial clearance on the connecting rod.

Fitting clearance

Connecting rod endfloat - standard clearance

0.15 ÷ 0.30 mm Connecting rod endfloat - standard

clearance 0.5 mm

- Check the correct radial clearance of the con­necting rod by holding the driving shaft with your
hands and, with a dial gauge fitted to the rod small
end, measuring the clearance, move the connect­ing rod vertically as shown in the figure.

Fitting clearance

Connecting rod radial - standard clearance

0.006 ÷ 0.018 mm Connecting rod max. - radial

clearance 0.25 mm

ENG - 99

Engine ET4 50

- Check that the half shaft surfaces are not scored
and with the aid of a gauge check the driving shaft
width as indicated in the figure.

Characteristic

Standard measure

45 mm

Removing the crankshaft bearings

- Remove the flywheel bearing fitted on the driving
shaft using the specific tool.

Specific tooling

004499Y Camshaft bearing extractor
004499Y001 Bearing extractor bell
004499Y002 Bearing extractor screw
004499Y006 Bearing extractor ring
004499Y034 Bearing extractor part

Refitting the crankshaft bearings

- Heat a new main bearing in an oil bath at 120°.

- Place the driving shaft on the support base and
insert the bearing with the aid of an adequate piece
of tube if necessary.

N.B.
USE A NEW BEARING WHEN REFITTING
WARNING
THE CENTRIFUGAL OIL FILTER IS IN THE FLYWHEEL

AXLE SHAFT. DO NOT WASH WITH SOLVENTS OR BLOW
COMPRESSED AIR SO THAT NO IMPURITIES LEAK OUT.

Specific tooling

020265Y Bearing fitting base
008119Y009 Tube to assemble shafts and

axles

ENG - 100