Page 4 of 506
EC020000
INTRODUCTION
Congratulations on your purchase of a
Yamaha YZ series. This model is the culmina-
tion of Yamaha’s vast experience in the pro-
duction of pacesetting racing machines. It
represents the highest grade of craftsmanship
and reliability that have made Yamaha a
leader.
This manual explains operation, inspection,
basic maintenance and tuning of your
machine. If you have any questions about this
manual or your machine, please contact your
Yamaha dealer.
NOTE:
As improvements are made on this model,
some data in this manual may become out-
dated. If you have any questions, please con-
sult your Yamaha dealer.
WARNING
PLEASE READ THIS MANUAL CAREFULLY
AND COMPLETELY BEFORE OPERATING
THIS MACHINE. DO NOT ATTEMPT TO
OPERATE THIS MACHINE UNTIL YOU
HAVE ATTAINED A SATISFACTORY
KNOWLEDGE OF ITS CONTROLS AND
OPERATING FEATURES AND UNTIL YOU
HAVE BEEN TRAINED IN SAFE AND
PROPER RIDING TECHNIQUES. REGULAR
INSPECTIONS AND CAREFUL MAINTE-
NANCE, ALONG WITH GOOD RIDING
SKILLS, WILL ENSURE THAT YOU SAFETY
ENJOY THE CAPABILITIES AND THE RELI-
ABILITY OF THIS MACHINE.
Page 10 of 506
EC050000
TO THE NEW OWNER
This manual will provide you with a good basic
understanding of features, operation, and
basic maintenance and inspection items of this
machine. Please read this manual carefully
and completely before operating your new
machine. If you have any questions regarding
the operation or maintenance of your machine,
please consult your Yamaha dealer.
NOTE:
This manual should be considered a perma-
nent part of this machine and should remain
with it even if the machine is subsequently
sold.
EC060000
NOTICE
Some data in this manual may become out-
dated due to improvements made to this
model in the future. If there is any question
you have regarding this manual or your
machine, please consult your Yamaha
dealer.
Page 20 of 506
EC0A0000
CONTENTS
CHAPTER 1
GENERAL INFORMATION
DESCRIPTION
........................................... 1-1
MACHINE IDENTIFICATION
..................... 1-2
IMPORTANT INFORMATION
.................... 1-3
CHECKING OF CONNECTION
................. 1-6
SPECIAL TOOLS
...................................... 1-7
CONTROL FUNCTIONS
............................ 1-9
FUEL AND ENGINE MIXING OIL
............ 1-12
STARTING AND BREAK-IN
.................... 1-13
TORQUE-CHECK POINTS
...................... 1-16
CLEANING AND STORAGE
................... 1-17
CHAPTER 2
SPECIFICATIONS
GENERAL SPECIFICATIONS
................... 2-1
MAINTENANCE SPECIFICATIONS
.......... 2-4
ENGINE
................................................... 2-4
CHASSIS
................................................. 2-8
YZ85
..................................................... 2-8
YZ85LW
.............................................. 2-10
ELECTRICAL
........................................ 2-14
GENERAL TORQUE
SPECIFICATIONS
................................... 2-15
DEFINITION OF UNITS
........................... 2-15
CABLE ROUTING DIAGRAM
................. 2-16
Page 22 of 506
CHAPTER 3
REGULAR INSPECTION AND
ADJUSTMENTS
MAINTENANCE INTERVALS................... 3-1
PRE-OPERATION INSPECTION
AND MAINTENANCE................................ 3-4
ENGINE...................................................... 3-5
CHASSIS................................................. 3-16
ELECTRICAL........................................... 3-36
CHAPTER 4
ENGINE
SEAT, FUEL TANK
AND SIDE COVERS.................................. 4-1
EXHAUST PIPE AND SILENCER............. 4-2
RADIATOR................................................ 4-3
CARBURETOR AND REED VALVE......... 4-6
CYLINDER HEAD, CYLINDER
AND PISTON........................................... 4-15
CLUTCH AND PRIMARY
DRIVEN GEAR........................................ 4-26
KICK SHAFT, SHIFT SHAFT
AND PRIMARY DRIVE GEAR................. 4-33
WATER PUMP......................................... 4-41
CDI MAGNETO........................................ 4-45
ENGINE REMOVAL................................. 4-49
CRANKCASE AND CRANKSHAFT........ 4-53
TRANSMISSION, SHIFT CAM
AND SHIFT FORK................................... 4-59
Page 58 of 506
GEN
INFO
1 - 16
TORQUE-CHECK POINTS
TORQUE-CHECK POINTS
Frame construction
Combined seat and fuel tank
Engine mounting
Steering Steering stem to
handlebar
Suspension Front Steering stem to front
fork
Rear For link type
Rear Installation of rear
shock absorber
Rear Installation of swin-
garm
Wheel Installation of wheel Front
Rear
Brake Front
Rear
Fuel systemFrame to rear frame
Fuel tank to frame
Frame to engine
Steering stem to upper bracket
Upper bracket to handlebar
Front fork to upper bracket
Front fork to lower bracket
Assembly of links
Link to frame
Link to rear shock absorber
Link to swingarm
Rear shock absorber to frame
Tightening of pivot shaft
Tightening of wheel axle
Tightening of wheel axle
Wheel to rear wheel sprocket
Brake caliper to front fork
Brake disc to wheel
Tightening of union bolt
Brake master cylinder to handlebar
Tightening of bleed screw
Brake caliper to bracket
Brake disc to wheel
Tightening of union bolt
Brake master cylinder to frame
Tightening of bleed screw
Fuel tank to fuel cock
NOTE:
Concerning the tightening torque, refer to
“MAINTENANCE SPECIFICATIONS” section
in the CHAPTER 2.
Page 69 of 506
SPEC
2 - 4
MAINTENANCE SPECIFICATIONS
MAINTENANCE SPECIFICATIONS
ENGINE
Item Standard Limit
Cylinder head:
Combustion chamber capacity 7.14 cm
3
(0.25 Imp oz, 0.24 US oz)----
Warp limit ---- 0.03 mm
(0.0012 in)
Cylinder:
Bore size 47.500 ~ 47.514 mm
(1.8701 ~ 1.8706 in)47.6 mm
(1.8740 in)
Taper limit ---- 0.05 mm
(0.0020 in)
Out of round limit ---- 0.01 mm
(0.0004 in)
Piston:
Piston to cylinder clearance 0.040 ~ 0.045 mm
(0.0016 ~ 0.0018 in)0.1 mm
(0.004 in)
Piston size “D”47.457 ~ 47.472 mm
(1.8684 ~ 1.8690 in)----
Measuring point “H”20 mm (0.79 in) ----
Piston off-set 1.0 mm (0.039 in)/EX-side ----
Piston pin bore inside diameter 14.004 ~ 14.015 mm
(0.5513 ~ 0.5518 in)14.040 mm
(0.5528 in)
Piston pin outside diameter 13.996 ~ 14.000 mm
(0.5510 ~ 0.5512 in)13.975 mm
(0.5502 in)
Piston ring:
Type Plain ----
Dimensions (B × T) 0.8 × 2.0 mm (0.031 × 0.079 in) ----
End gap (installed) 0.30 ~ 0.45 mm
(0.012 ~ 0.018 in)0.80 mm
(0.031 in)
Side clearance (installed) 0.030 ~ 0.065 mm
(0.001 ~ 0.003 in)0.1 mm
(0.004 in)
B
T
Page 70 of 506
SPEC
2 - 5
MAINTENANCE SPECIFICATIONS
Crankshaft:
Crank width “A”44.90 ~ 44.95 mm
(1.768 ~ 1.770 in)----
Runout limit “C”0.03 mm (0.0012 in) 0.08 mm
(0.003 in)
Big end side clearance “D”0.20 ~ 0.70 mm
(0.008 ~ 0.028 in)----
Small end free play “F”0.5 ~ 1.2 mm
(0.020 ~ 0.047 in)2.0 mm
(0.08 in)
Clutch:
Friction plate thickness 2.9 ~ 3.1 mm
(0.114 ~ 0.122 in)2.7 mm
(0.106 in)
Quantity 7 ----
Clutch plate thickness 1.8 ~ 2.2 mm (0.071 ~ 0.087 in) ----
Quantity 6 ----
Warp limit ---- 0.1 mm
(0.004 in)
Clutch spring free length 34.0 mm (1.34 in) 32.0 mm
(1.26 in)
Quantity 5 ----
Clutch housing thrust clearance 0.10 ~ 0.35 mm
(0.0039 ~ 0.0138 in)----
Clutch housing radial clearance 0.022 ~ 0.051 mm
(0.0009 ~ 0.0020 in)----
Clutch release method Inner push, cam push ----
Shifter:
Shifter type Cam drum and guide bar ----
Guide bar bending limit ---- 0.05 mm
(0.002 in)
Kickstarter:
Type Kick and mesh type ----
Carburetor:
Type/manufacturer PWK28/ KEIHIN ----
I. D. mark 5PA1 00 ----
Main jet (M.J) #138 ----
Jet needle-clip position (J.N) NBKF-2 ----
Main nozzle (N.J)ø3.4 ----
Cutaway (C.A) 3.0 ----
Pilot jet (P.J) #45 ----
Pilot air screw (example) (P.A.S) 2 ----
Starter jet (G.S) #62 ----
Float height (F.H) 18 ~ 20 mm (0.71 ~ 0.79 in) ----Item Standard Limit
Page 71 of 506
SPEC
2 - 6
MAINTENANCE SPECIFICATIONS
Reed valve:
Thickness “T”0.42 mm (0.017 in) ----
Valve stopper height 7.4 ~ 7.8 mm (0.291 ~ 0.307 in) ----
Valve bending limit ---- 0.2 mm
(0.008 in)
Cooling:
Radiator core size
Width 117.8 mm (4.64 in) ----
Height 240 mm (9.45 in) ----
Thickness 32 mm (1.26 in) ----
Radiator cap opening pressure 95 ~ 125 kPa (0.95 ~ 1.25 kg/cm
2,
13.5 ~ 17.8 psi)----
Radiator capacity 0.32 L (0.28 Imp qt, 0.34 US qt) ----
Water pump
Type Single-suction centrifugal pump ----Item Standard Limit
