Gilera 633721 Instruction manual

WORKSHOP MANUAL
633721 - 633728
Nexus 500 euro 3

WORKSHOP
MANUAL
Nexus 500 euro 3
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 shown in this publication are available in all countries. The availability of single versions
should be checked at the official Piaggio sales network.
"©Copyright2005-PIAGGIO&C.S.p.A.Pontedera.Allrightsreserved.Reproductionofthispublication
in whole or in part is prohibited."
PIAGGIO & C. S.p.A. - Q.C.S./After sales V.le Rinaldo Piaggio, 23 - 56025 PONTEDERA (Pi)
www.piaggio.com

WORKSHOP MANUAL
Nexus 500 euro 3
This workshop manual has been drawn up by Piaggio & C. Spa to be used by the workshops of Piaggio-
Gilera dealers. This manual is addressed to Piaggio service mechanics who are supposed to have a
basic knowledge of mechanics principles and of scooter mounting techniques and procedures. Any
important changes made to the scooters or to specific mounting operations will be promptly reported by
updates to this manual. Nevertheless, no mounting 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 special
tools, along with the special 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 Sectionsmarked with this symbol indicatethe correct use of thevehicle
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
ELECTRICAL SYSTEM ELE SYS
ENGINE FROM VEHICLE ENG VE
ENGINE ENG
INJECTION INJEC
SUSPENSIONS SUSP
BRAKING SYSTEM BRAK SYS
COOLING SYSTEM COOL SYS
CHASSIS CHAS
PRE-DELIVERY PRE DE
TIME TIME

INDEX OF TOPICS
CHARACTERISTICS CHAR

This section describes the general specifications of the vehicle.
Rules
This section describes general safety rules for any maintenance operations performed on the vehicle.
Safety rules
•Should it be necessary to keep the engine running while servicing, make sure that the area
or room is well ventilated, and use special exhaust fans, if required. 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. Sul-
phuricacidis highly corrosive; in the event of contact with your eyesorskin, 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 in some conditions it can be explosive. Do not smoke in the
working area, and avoid open flames or sparks.
•Clean the brake pads in a well ventilated environment, directing the compressed air jet so
as to not inhale the dust produced by the wear of the friction material. Even though the latter
contains no asbestos, dust inhalation 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 special tools designed for this scooter.
•Always use new gaskets, sealing rings and split pins upon reassembly.
•After removal, clean the components using non-flammable or low fire-point solvent. Lubri-
cate all the work surfaces except the tapered couplings before refitting.
•After reassembly, check that all components have been installed properly and that they are
in good working order.
•Forremoval, overhaul and reassemblyoperations use only tools provided with metric meas-
ures. Metric bolts, nuts and screws are not interchangeable with coupling members with
English measurement. Using unsuitable coupling members and tools may damage the
scooter.
•Should any interventions to the scooter electrical system be required, check that the elec-
trical connections - especially earth and battery connections - have been implemented
properly.
Nexus 500 euro 3 Characteristics
CHAR - 7

Vehicle identification
Characteristic
Engine prefix:
M351M
Chassis prefix:
ZAPM35200
Dimensions and mass
WEIGHT
Specification Desc./Quantity
Dry weight 199 kg
Width 765 mm
Length 2090 mm
Wheel base 1515 mm
Saddle height 780 mm
Height 1045 mm
Characteristics Nexus 500 euro 3
CHAR - 8

Engine
ENGINE
Specification Desc./Quantity
Engine Single-cylinder, four-stroke
Bore 92 mm
Stroke 69 mm
Cubic capacity 460 cm³
Compression ratio 10.5: 1
Timing system Single overhead camshaft with integrated tone wheel, control
from flywheel side chain, 4 valves and automatic start-up valve
lifting device.
Valve clearance: intake 0.15 mm (when cold)
Valve clearance: discharge 0.15 mm (when cold)
Valve clearance adjustment By threaded adjuster on the rockers
Engine idle speed 1500 ± 50 rpm
Air filter sponge, impregnated with mixture (50% petrol and 50% oil)
CO % value (measured at the intake manifold) 1 - 1.5%
Starting system Electric starter system with freewheel.
Lubrication By trochoidal pump (inside the crankcase), pressure adjust-
ment by-pass and oil filter.
Lubrication pressure 4 bar
Minimum allowed (at 100° C) 0.8 bar
Fuel supply Electronic injection system with electric fuel pump, Ø 38 mm
throttle body and single injector.
Max. power (shaft) 29 kW (39 CV) at 7250 rpm
Max. torque (shaft) 40 N·m (4 kgm) at 5500 rpm
Cooling system Fluid circulation through a motor-driven pump, 3-way thermo-
stat and electric fan.
Transmission
TRANSMISSIONS
Specification Desc./Quantity
Transmission With automatic expandable pulley variator with torque server,
V belt, automatic clutch, gear reduction unit and transmission
housing with forced air circulation cooling.
Capacities
CAPACITY
Specification Desc./Quantity
Engine oil (empty) 1.7 lt.
Engine oil (at oil and filter change) 1.5 lt.
Fuel tank (including reserve approx. 2 litres) approx. 14.5 litres
Rear hub approx. 250 cc.
Cooling system approx. 1.8 litres
Front fork approx. 242 ± 3 cc (in each fork leg)
Electrical system
ELECTRICAL SYSTEM
Specification Desc./Quantity
Electronic ignition inductive, high efficiency integrated with the injection system,
with variable timing and separate HV coil.
Spark plug NGK CR7EKB
Spark plug CHAMPION RG6YC
Nexus 500 euro 3 Characteristics
CHAR - 9

Specification Desc./Quantity
Battery Dry-cell lead-acid battery, 12V-14Ah
Generator Three-phase alternating current
Frame and suspensions
CHASSIS AND SUSPENSIONS
Specification Desc./Quantity
Chassis Welded steel pipes with pressed sheet metal stiffening
Front suspension Hydraulic telescopic fork with diameter 41 mm stems
Front fork max. stroke 104 mm
Rear suspension Type "Power drive": Shock absorber (with double-
acting helicoidal spring and adjustment of the
spring preload in 7 positions) mounted in horizon-
tal position, connected to a connecting rod pivoted
to a strut with variable length.
By varying the length of the strut it is possible to
modify the geometry and balance of the rear axle
(15 positions).
The motor has a fixed connection to the frame by
means of a shaft (direct link).
Brakes
BRAKES
Specification Desc./Quantity
Front brakes Twin discs of stainless steel, dia. 260 mm, with floating calliper
and twin 28 mm diameter plungers (Brembo) at front right and
twin 26 mm diameter plungers (Brembo) at front left.
Rear brakes Disc of stainless steel, dia. 240 mm, with fixed calliper and two
opposed 34 mm diameter plungers
Wheels and tyres
WHEELS AND TYRES
Specification Desc./Quantity
Rims in light alloy: Front 3.50 x 15"
Rims in light alloy: Rear 4.50 x 14"
Rear tyres Bridgestone 160/60-R14" Tubeless 65H
Front tyres Bridgestone 120/70-R15" Tubeless 56H
Tyre pressure (cold) front 2.1 bar
Tyre pressure (cold) rear 2.3 bar (2.5 bar with passenger)
N.B.
CHECK AND ADJUST TYRE PRESSURE WITH TYRES AT AMBIENT TEMPERATURE. ADJUST
PRESSURE ACCORDING TO THE WEIGHT OF RIDER AND ACCESSORIES.
CAUTION
IT IS MANDATORY TO ADOPT EXCLUSIVELY "S" CLASS TYRES, WHICH GUARANTEE COR-
RECT VEHICLE PERFORMANCE AT THE DIFFERENT SCOOTER SPEEDS. USING ANY OTHER
TYRE MAY RESULT IN VEHICLE INSTABILITY. IT IS ADVISABLE TO USE TYRE TYPES REC-
OMMENDED BY PIAGGIO.
Characteristics Nexus 500 euro 3
CHAR - 10

Tightening Torques
FRAME
Name Torque in Nm
Electric pump locking ring nut 20
BRAKE SYSTEM
Name Torque in Nm
Brake calliper coupling 20 - 24
Front brake disc mounting 5 ÷ 6 •
Rear brake disc mounting 11 ÷ 13
Front brake calliper mounting on fork 20 ÷ 25
Rear calliper support on crankcase retainer 20 ÷ 25
Pipe / brake calliper coupling 20 ÷ 25
Circuit bleed calliper fitting 12 - 16
Plastic protection retaining screw 5 - 6
Coupling for oil on the integral braking system pump 16 ÷ 20
Couplingontheintegralbrakingsystemdevice(fromthepump) 20 ÷ 25
Front brake calliper - integral braking system device coupling 20 ÷ 25
Rear brake calliper - integral braking system device coupling 20 ÷ 25
• Locking with Loctite threadlock medium 243
FRONT SUSPENSION
Name Torque in Nm
Front wheel axle 45 ÷ 50
Holding torque of lower ring nut 20 ÷ 25
Fork stem mounting to the plate 20 ÷ 25
Steering lower ring nut 10 - 13 **
Upper steering ring nut 36 - 39
Stem upper cap 35 - 55
Fixing screw handlebar to steering tube 45 ÷ 50
Pumping element fixing screw 25 - 35
Safety screw on fork leg 6 ÷ 7
Wheel fastening screws 33 - 37
* tighten and loosen completely. ** tighten and loosen by 90°.
REAR SUSPENSION
Name Torque in Nm
Engine - chassis fixing pin 100 - 120
Central stand retainers 25 ÷ 30
Muffler heat guard retainers 6 - 8
Side stand clamp 15 ÷ 20
Rear wheel axle 104 ÷ 126
Connection of rear shock absorber to support connecting rod 38 - 46
Rear shock absorber retainer to the chassis 38 - 46
Upper strut connection 56 - 70
Clamping of connection rod supporting strut and shock ab-
sorber to frame 73 - 80
Clamping of rear strut support to hub cover 20 - 25
Lower strut clamping 30 - 35
Rear strut support clamping to crankcase 11 - 13
Assembly plate mounting on strut support 11 - 13
• Locking with Loctite threadlock medium 243
ENGINE ASSEMBLY
Name Torque in Nm
Starter motor screws 11 ÷ 13
THERMAL GROUP AND TIMING SYSTEM
Name Torque in Nm
Spark plug 12 ÷ 14
Nexus 500 euro 3 Characteristics
CHAR - 11

Name Torque in Nm
Head fixing stud bolts ***
Head fixing nuts 10 - 12
Exhaust / intake head fixing nuts 10 - 12
Head lubrication control jet 5 - 7
coolant temperature sensor: 10 - 12
Lambda probe on exhaust manifold 10 - 12
injector fixing screw 3 ÷ 4
Counterweight screw 7 ÷ 8.5
Tensioner sliding block fixing screw 10 - 14
Rpm timing sensor fixing screw 3 - 4
Valve lifter mass stop bell fixing screws 30 - 35
Inlet manifold screws 11 ÷ 13
Tappet cover fixing screws 7 - 9
Throttle body fixing screws 11 ÷ 13
Head fixing screws 10 - 12
Camshaft retaining bracket screws: 4 ÷ 6
Tightener screw: 5 - 6
Tightener fastening screws: 11 ÷ 13
*** Apply a preliminary torque of 7 Nm in a crossed sequence. - Tighten by 90° in a crossed sequence. - tighten again by 90° in
a criss-crossed sequence.
CRANKCASE AND CRANKSHAFT
Name Torque in Nm
Countershaft fixing nut 25 ÷ 29
Engine oil filter 12 - 16
Engine oil drainage plug 24 ÷ 30
Engine-crankcase coupling screws 11 ÷ 13
Oil pump screws 5 - 6
Gear mounting on crankshaft screws 10 -12
Bulkhead screws for oil pump housing cover 8 - 10
FINAL REDUCTION
Name Torque in Nm
Rear hub cover screws 24 ÷ 27
TRANSMISSION COVER
Name Torque in Nm
Driven pulley nut 92 - 100
Driving pulley nut 160 - 175
Anti-vibration roller screw 16.7 ÷ 19.6
M8 retainers for transmission cover 23 ÷ 26
M6 retainer 11 ÷ 13
Anti-vibration roller retainer 17 - 19
Clutch ring nut 65 - 75
Air conveyor screws 11 ÷ 12
Water pump cover screws 3 ÷ 4
External transmission cover screws 7 ÷ 9
Flywheel cover screws 11 - 13
FLYWHEEL COVER
Name Torque in Nm
Chain guide sliding block retain plate fastening screws 3 ÷ 4
Flywheel fixing nut 115 - 125
Stator retainers 8 - 10
Blow-by recovery duct fixing screws 3 - 4
Screw fixing freewheel to flywheel 13 ÷ 15
Stator cable harness guide bracket screws 3 - 4
Supporting screws with bulkhead 0.3 - 0.4
Minimum oil pressure sensor 12 ÷ 14
Water pump impeller 4 ÷ 5
Characteristics Nexus 500 euro 3
CHAR - 12

LUBRICATION
Name Torque in Nm
Oil pump cover screws 0.7 ÷ 0.9
Screws fixing oil pump to crankcase 5 - 6
See also
Refitting
Refitting
Fuel tank
Overhaul
Overhaul data
This section provides the main information for scooter servicing.
Assembly clearances
Cylinder - piston assy.
(Values in mm)
HEIGHT AT WHICH THE DIAMETER SHOULD BE MEASURED
Specification Desc./Quantity
A: 10 mm
B: 43 mm
CATEGORIES OF COUPLING
Name Initials Cylinder Piston Play on fitting
Cylinder Piston A 91.990 - 91.997 91.954 - 91.961 0.029 - 0.043
Cylinder Piston B 91.997 - 92.004 91.961 - 91.968 0.029 - 0.043
Cylinder Piston C 92.004 - 92.011 91.968 - 91.975 0.029 - 0.043
Cylinder Piston D 92.011 - 92.018 91.975 - 91.982 0.029 - 0.043
N.B.
THE PISTON MUST BE INSTALLED WITH THE ARROW FACING TOWARDS THE EXHAUST SIDE,
THE PISTON RINGS MUST BE INSTALLED WITH THE WORD «TOP» OR THE STAMPED MARK
FACING UPWARDS.
Nexus 500 euro 3 Characteristics
CHAR - 13

Piston rings
* Fit rings «2» and «3» with the word «TOP» facing upwards.
** Position the openings in the rings as shown here.
*** Value «A» of sealing ring inside the cylinder
**** Ring opening
SEALING RINGS
Name Initials Cylinder Piston Play on fitting
1st Compression ring A 0.15 ÷ 0.35 0.5 </>
Middle piston ring A 0.25 ÷ 0.50 0.65 </>
Oil scraper ring A 0.25 ÷ 0.50 0.65 </>
Crankcase - crankshaft - connecting rod
Crankcase / countershaft coupling
Besides considering it should match the crankshaft, the crankcase is chosen according to the centre
to centre distance between the seat of the crankshaft and that of the contra-rotating shaft.
Both the centre to centre distance and the pair of gears driving the contra-rotating shaft are divided into
two types (A and B) to be matched (Awith Aand Bwith B).
This selection is useful to keep the difference between the working distance of the gears and their
distance without clearance at a given value in order to avoid abnormal noise.
TYPE A
Specification Desc./Quantity
Centre to centre distance of the gears without clearance 76.937 ÷ 76.867
Centre to centre distance on the crankcase 77.022 ÷ 76.992
TYPE B
Specification Desc./Quantity
Centre to centre distance of the gears without clearance 76.907 ÷ 76.837
Centre to centre distance on the crankcase 76.992 ÷ 76.962
The gears with centre to centre distance without clearance between 76.867 and 76.907 are considered
universal and can be fitted to either crankcase type.
Either the pair of gears or the crankcase is identified with the letter referring to the type (on the crank-
case, this mark is found at the cylinder mouth, flywheel side).
Characteristics Nexus 500 euro 3
CHAR - 14

Diameter of crankshaft bearings.
Measure the capacity on both axes x-y.
CRANKSHAFT
Specification Desc./Quantity
Cat. 1 Standard diameter: 40.010 ÷ 40.016
Cat. 2 Standard diameter: 40.016 ÷ 40.022
Crankshaft alignment
Specific tooling
020335Y Magnetic support for dial gauge
MAX. ADMISSIBLE DISPLACEMENT
Specification Desc./Quantity
A = 0.15 mm
B = 0.010 mm
C = 0.010 mm
D = 0.10 mm
Nexus 500 euro 3 Characteristics
CHAR - 15

AXIAL CLEARANCE BETWEEN CRANKSHAFT AND CONNECTING ROD
Name Description Dimensions Initials Quantity
Transmission-side
shoulder 0.8 ± 0.025 A D= 0.20 - 0.40
Transmission-side half-
shaft 19.6 + 0.050 B D= 0.20 - 0.40
Connecting rod 22 0.10-0.15 C D= 0.20 - 0.40
Flywheel-side shoulder 13 ± 0.025 F D= 0.20 - 0.40
Flywheel-side half-shaft 19.6 +0.050 E D= 0.20 - 0.40
Complete drive shaft 63.5+0.1-0.05 G D= 0.20 - 0.40
Characteristic
Drive shaft / crankcase axial clearance:
0.1 - 0.5 mm (when cold)
Slot packing system
Shimming system for limiting the compression ra-
tio Rc = 10.5 : 1
DISTANCE «A» IS A PROTRUSION OR RE-
CESS VALUE OF THE PISTON CROWN WITH
RESPECT TO THE CYLINDER PLANE.
DISTANCE «A» HELPS DETERMINE THE
THICKNESS OF GASKET «B» THAT HAS TO
BE FITTED TO THE CYLINDER HEAD IN OR-
DER TO RESTORE COMPRESSION RATIO.
BASE GASKET «B» MUST BE THICKER THE
MORE THE PLANE FORMED BY THE PISTON
TOP PROTRUDES FROM THE PLANE
FORMED BY THE CYLINDER HEAD. ON THE
OTHER HAND, THE MORE THE PISTON TOP IS
RECESSED INTO THE CYLINDER TOP PLANE,
THE SMALLER THE GASKET THICKNESS.
BASE GASKET THICKNESS
Name Measure A Thickness
«A» MEASURE TAKEN - 0.185 - - 0.10 0.4 ± 0.05
«A» MEASURE TAKEN - 0.10 - + 0.10 0.6 ± 0.05
«A» MEASURE TAKEN + 0.10 ÷ + 0.185 0.8 ± 0.05
N.B.
VALUES INDICATED WITH «-» REFER TO PISTON CROWN RECESSES WITH RESPECT TO THE
CYLINDER PLANE.
Characteristics Nexus 500 euro 3
CHAR - 16

N.B.
DISTANCE «A» MUST BE MEASURED WITHOUT ANY GASKET FITTED AT «B»
Products
PRODUCTS
Product Description Specifications
AGIP ROTRA 80W-90 Rear hub oil SAE 80W/90 Oil that exceeds the re-
quirements of API GL3 specifications
AGIP FILTER OIL Oil for air filter sponge Mineral oil with specific additives for in-
creased adhesiveness
AGIP CITY HI TEC 4T Engine oil SAE5W-40,APISL,ACEAA3,JASOMA
Synthetic oil
AGIP BRAKE 4 Brake fluid FMVSS DOT 4 Synthetic fluid
AGIP PERMANENT SPEZIAL coolant Monoethylene glycol-based antifreeze
fluid, CUNA NC 956-16
AUTOSOL METAL POLISH Muffler cleaning paste specialproduct for cleaningandpolishing
stainless steel muffler
AGIP GP 330 Grease for brake levers, throttle White calcium complex soap-based
spraygrease with NLGI2;ISO-L-XBCIB2
AGIP CITY TEC 2T Mixer oil synthetic oil for 2-stroke engines: JASO
FC, ISO-L-EGD
Nexus 500 euro 3 Characteristics
CHAR - 17

INDEX OF TOPICS
TOOLING TOOL

GOOD SPECIAL TOOLS
Stores code Description
001330Y Tool for fitting steering seats
001467Y002 Driver for OD 73 mm bearing
001467Y006 Pliers to extract 20 mm bearings
001467Y007 Driver for OD 54-mm bearings
001467Y008 Pliers to extract 17 mm ø bearings
001467Y014 Pliers to extract ø 15-mm bearings
Nexus 500 euro 3 Tooling
TOOL - 19

Stores code Description
001467Y031 Bell
001467Y034 Pliers to extract ø 15-mm bearings
001467Y035 Belle for OD 47-mm bearings
002465Y Pliers for circlips
006029Y Punch for fitting fifth wheel seat on steer-
ing tube
020004Y Punch for removing fifth wheels from
headstock
Tooling Nexus 500 euro 3
TOOL - 20