fuel YAMAHA YZ85 2003 Owner's Manual

4 - 1
ENG
EC400000
ENGINE
SEAT, FUEL TANK AND SIDE COVERS
5PA40010
Extent of removal:
1 Seat removal
2 Fuel tank removal
3 Side covers removal
4 Number plate removal
Extent of removal Order Part name Q’ty Remarks
Preparation for removalSEAT, FUEL TANK AND SIDE
COVERS REMOVAL
Turn the fuel cock to “OFF”.
Disconnect the fuel hose.
1Seat 1
2 Air scoop 1
3 Bolt (fuel tank) 2
4 Fuel tank 1
5 Left side cover 1
6 Right side cover 1
7 Number plate 1
13
4
2
3
SEAT, FUEL TANK AND SIDE COVERS

4 - 2
ENGEXHAUST PIPE AND SILENCER
EC4S0000
EXHAUST PIPE AND SILENCER
5PA40020
Extent of removal:
1 Silencer removal
2 Exhaust pipe removal
Extent of removal Order Part name Q’ty Remarks
EXHAUST PIPE AND
SILENCER REMOVAL
Preparation for removal Right side cover Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
1 Bolt (silencer) 1
2 Silencer 1
3 Exhaust pipe spring 2
4 Bolt (exhaust pipe) 2
5Exhaust pipe
1
1
2

4 - 3
ENGRADIATOR
EC450001
RADIATOR
5PA40030
Extent of removal:
1 Radiator removal
Extent of removal Order Part name Q’ty Remarks
RADIATOR REMOVAL
Preparation for removal Drain the coolant. Refer to “COOLANT REPLACEMENT”
section in the CHAPTER 3.
Air scoop Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
1 Radiator guard 1
2 Radiator hose clamp 4 Only loosening.
3 Radiator hose 1 1
4 Radiator hose 2 1
5Radiator 1
6 Radiator breather hose 1
1

4 - 8
ENGCARBURETOR AND REED VALVE
HANDLING NOTE
CAUTION:
Do not disassemble the venturi block
1
because it will cause a drop in carburetor
performance.
5PA40110
EC463000
REMOVAL POINTS
EC463110
Throttle valve
1. Remove:

Throttle valve 1

Ring 2

Spring (throttle valve) 3

Mixing chamber top 4

Throttle cable 5
NOTE:
While compressing the spring (throttle valve),
disconnect the throttle cable.
5PA40120
INSPECTION
Pilot air screw
1. Remove:

Pilot air screw 1
NOTE:
To optimize the fuel flow at a small throttle
opening, each machine’s pilot air screw has
been individually set at the factory. Before
removing the pilot air screw, turn it in fully and
count the number of turns. Record this number
as the factory-set number of turns out.
Carburetor
1. Inspect:

Carburetor body
Contamination → Clean.
NOTE:

Use a petroleum based solvent for cleaning.
Blow out all passages with compressed air.

Never use a wire.
5PA40130
5PA40130

4 - 15
ENGCYLINDER HEAD, CYLINDER AND PISTON
EC470000
CYLINDER HEAD, CYLINDER AND PISTON
EC478000
CYLINDER HEAD AND CYLINDER
5PA40390
Extent of removal:
1 Cylinder head removal
2 Cylinder removal
Extent of removal Order Part name Q’ty Remarks
CYLINDER HEAD AND CYLIN-
DER REMOVAL
Preparation for removal Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Exhaust pipe and silencer Refer to “EXHAUST PIPE AND
SILENCER” section.
Radiator hose 1 Disconnect at cylinder head side.
Radiator hose 2 Disconnect at radiator side.
1 Spark plug 1
2 Nut (cylinder head) 4 Loosen each nut 1/4 turn, and remove
them after all nuts are loosened.
3 Cylinder head 1
4 Nut (cylinder) 4
5 Cylinder 1
1
2

4 - 45
ENG
EC4L0000
CDI MAGNETO
5PA41380
Extent of removal:
1 CDI magneto removal
Extent of removal Order Part name Q’ty Remarks
CDI MAGNETO REMOVAL
Preparation for removal Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Disconnect the CDI magneto lead.
1 Left crankcase cover 1
2 Nut (rotor) 1 Use special tool.
Refer to “REMOVAL POINTS”.
3 Rotor 1
4 Stator 1
5Woodruff key
1
1
CDI MAGNETO

4 - 49
ENG
EC4M0000
ENGINE REMOVAL
5PA41490
Extent of removal Order Part name Q’ty Remarks
ENGINE REMOVAL
Preparation for removal Hold the machine by placing the
suitable stand under the frame.
WARNING
Support the machine securely so there is no
danger of it falling over.
Drain the coolant. Refer to “COOLANT REPLACEMENT”
section in the CHAPTER 3.
Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Carburetor Refer to “CARBURETOR AND REED
VALVE” section.
Exhaust pipe and silencer Refer to “EXHAUST PIPE AND
SILENCER” section.
Clutch cable Disconnect at engine side.
Radiator hose 1 Disconnect at cylinder head side.
Radiator hose 2 Disconnect at water pump side.
Spark plug cap
Disconnect the CDI magneto
lead.
ENGINE REMOVAL

5 - 45
CHAS
7. Install:

Engine stop switch 1

Clutch lever holder 2

Bolts (clutch lever holder) 3

Clamp 4
NOTE:
The engine stop switch and clutch lever holder
should be installed according to the dimen-
sions shown.
5PA51420
T R..4 Nm (0.4 m · kg, 2.9 ft · lb)
5PA51430
8. Install:

Clutch cable 1
NOTE:
Apply the lithium soap base grease on the
clutch cable end.
5PA51440
9. Adjust:

Clutch lever free play
Refer to “CLUTCH ADJUSTMENT” section
in the CHAPTER 3.
10. Clamp the clamp portion a of the number
plate to the handlebar.
11. Insert the end of the fuel tank breather
hose 1 into the hole of the steering stem.
5PA51450
HANDLEBAR

5 - 58
CHASREAR SHOCK ABSORBER
EC580000
REAR SHOCK ABSORBER
5PA51870
Extent of removal:
1 Rear shock absorber removal
2 Rear shock absorber disassembly
Extent of removal Order Part name Q’ty Remarks
Preparation for removalREAR SHOCK ABSORBER
REMOVAL
Hold the machine by placing the
suitable stand under the engine.
WARNING
Support the machine securely so there is no
danger of it falling over.
Seat Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section in the CHAPTER 4.
Silencer Refer to “EXHAUST PIPE AND
SILENCER” section in the CHAPTER 4.
1 Clamp (air cleaner joint) 1 Only loosening.
2Rear frame 1
3 Bolt (rear shock absorber-relay
arm)1 Hold the swingarm.
4 Bolt (rear shock absorber-frame) 1
5 Rear shock absorber 1
6 Locknut 1 Only loosening.
7 Adjuster 1 Only loosening.
8 Spring guide 1
9 Spring (rear shock absorber) 1
1
2

6 - 2
–+ELECIGNITION SYSTEM
EC620000
IGNITION SYSTEM
INSPECTION STEPS
Use the following steps for checking the possibility of the malfunctioning engine being attributable to
ignition system failure and for checking the spark plug which will not spark.
*marked: Only when the ignition checker is used.
NOTE:

Remove the following parts before inspection.
1) Seat
2) Fuel tank

Use the following special tools in this inspection.
Dynamic spark tester:
YM-34487
Ignition checker:
90890-06754Pocket tester:
YU-3112-C/90890-03112
Spark gap test*Clean or replace
spark plug.
Check entire ignition
system for connection.Repair or replace.
Check engine stop switch. Replace.
Check ignition coil. Primary coil Replace.
Secondary coil Replace.
Check spark plug cap. Replace.
Check CDI magneto. Pickup coil Replace.
Charging coil Replace.
Replace CDI unit.
No spark
OK
OK
OK
OK
OK
Spark
No good
No good
No good
No good
No good
No good
No good