Congratulations on your purchase of a
Yamaha WR series. This model is the culmination of Yamaha’s vast experience in the production 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.
OTE:
As improvements are made on this model,
some data in this manual may become outdated. If you have any questions, please consult 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 MAINTENANCE, ALONG WITH GOOD RIDING
SKILLS, WILL ENSURE THAT YOU SAFETY
ENJOY THE CAPABILITIES AND THE RELIABILITY OF THIS MACHINE.
IMPORTANT NOTICE
THIS MACHINE IS DESIGNED STRICTLY
FOR COMPETITION USE, ONLY ON A
CLOSED COURSE. It is illegal for this
machine to be operated on any public street,
road, or highway. Off-road use on public lands
may also be illegal. Please check local regulations before riding.
SAFETY INFORMATION
1. THIS MACHINE IS TO BE OPERATED
BY AN EXPERIENCED RIDER ONLY.
Do not attempt to operate this
machine at maximum power until you
are totally familiar with its characteristics.
2. THIS MACHINE IS DESIGNED TO BE
RIDDEN BY THE OPERATOR ONLY.
Do not carry passengers on this
machine.
3. ALWAYS WEAR PROTECTIVE
APPAREL.
When operating this machine, always
wear an approved helmet with goggles or a face shield. Also wear heavy
boots, gloves, and protective clothing. Always wear proper fitting clothing that will not be caught in any of
the moving parts or controls of the
machine.
4. ALWAYS MAINTAIN YOUR MACHINE
IN PROPER WORKING ORDER.
For safety and reliability, the machine
must be proerly maintained. Always
perform the pre-operation checks
indicated in this manual. Correcting a
mechanical problem before you ride
may prevent an accident.
5. GASOLINE IS HIGHLY FLAMMABLE.
Always turn off the engine while refueling. Take care to not spill any gasoline on the engine or exhaust system.
Never refuel in the vicinity of an open
flame, or while smoking.
6. GASOLINE CAN CAUSE INJURY.
If you should swallow some gasoline,
inhale excess gasoline vapors, or
allow any gasoline to get into your
eyes, contact a doctor immediately. If
any gasoline spills onto your skin or
clothing, immediately wash skin
areas with soap and water, and
change your clothes.
7. ONLY OPERATE THE MACHINE IN AN
AREA WITH ADEQUATE VENTILATION.
Never start the engine or let it run for
any length of time in an enclosed
area.
Exhaust fumes are poisonous. These
fumes contain carbon monoxide,
which by itself is odorless and colorless. Carbon monoxide is a dangerous gas which can cause
unconsciousness or can be lethal.
8. PARK THE MACHINE CAREFULLY;
TURN OFF THE ENGINE.
Always turn off the engine if you are
going to leave the machine. Do not
park the machine on a slope or soft
ground as it may fall over.
9. THE ENGINE, EXHAUST PIPE, MUFFLER, AND OIL TANK WILL BE VERY
HOT AFTER THE ENGINE HAS BEEN
RUN.
Be careful not to touch them or to
allow any clothing item to contact
them during inspection or repair.
10. PROPERLY SECURE THE MACHINE
BEFORE TRANSPORTING IT.
When transporting the machine in
another vehicle, always be sure it is
properly secured and in an upright
position and that the fuel cock is in
the “OFF” position. Otherwise, fuel
may leak out of the carburetor or fuel
tank.
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.
OTE:
This manual should be considered a permanent 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 outdated 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.
EC070001
F.I.M. MACHINE WEIGHTS:
Weights of machines without fuel
The minimum weights for motocross
machines are:
for the class 125 cc....................... minimum
88 kg (194 lb)
for the class 250 cc....................... minimum
98 kg (216 lb)
for the class 500 cc....................... minimum
102 kg (225 lb)
In modifying your machine (e.g., for weight
reduction), take note of the above limits of
weight.
EC080000
WARNING
HOW TO USE
THIS MANUAL
EC081000
PARTICULARLY IMPORTANT
INFORMATION
The Safety Alert Symbol means ATTENTION!
BECOME ALERT! YOUR SAFETY IS
INVOLVED!
Failure to follow WARNING instructions could
result in severe injury or death to the machine
operator, a bystander, or a person inspecting
or repairing the machine.
CAUTION:
A CAUTION indicates special precautions that
must be taken to avoid damage to the
machine.
NOTE:
A NOTE provides key information to make procedures easier or clearer.
EC082000
FINDING THE REQUIRED PAGE
1. This manual consists of seven chapters;
“General information”, “Specifications”,
“Regular inspection and adjustments”,
“Engine”, “Chassis”, “Electrical” and “Tun-
ing”.
2. The table of contents is at the beginning of
the manual. Look over the general layout of
the book before finding then required chapter and item.
Bend the book at its edge, as shown, to
find the required fore edge symbol mark
and go to a page for required item and
description.
EC083000
MANUAL FORMAT
All of the procedures in this manual are organized in a sequential, step-by-step format. The information has been complied to provide the mechanic with an easy to read, handy reference that contains
comprehensive explanations of all disassembly, repair, assembly, and inspection operations.
In this revised format, the condition of a faulty component will precede an arrow symbol and the
course of action required will follow the symbol, e.g.,
• Bearings
Pitting/damage → Replace.
EC084002
HOW TO READ DESCRIPTIONS
To help identify parts and clarify procedure steps, there are exploded diagrams at the start of each
removal and disassembly section.
1. An easy-to-see exploded diagram 1 is provided for removal and disassembly jobs.
2. Numbers 2 are given in the order of the jobs in the exploded diagram. A number that is
enclosed by a circle indicates a disassembly step.
3. An explanation of jobs and notes is presented in an easy-to-read way by the use of symbol
marks 3. The meanings of the symbol marks are given on the next page.
4. A job instruction chart 4 accompanies the exploded diagram, providing the order of jobs, names
of parts, notes in jobs, etc.
5. Extent of removal 5 is provided in the job instruction chart to save the trouble of an unneces-
sary removal job.
6. For jobs requiring more information, the step-by-step format supplements 6 are given in addi-
tion to the exploded diagram and job instruction chart.
12
GEN
INFO
34
SPEC
INSP
ADJ
56
CHAS
ENG
–+
ELEC
ILLUSTRATED SYMBOLS
(Refer to the illustration)
Illustrated symbols 1 to 7 are designed as
thumb tabs to indicate the chapter’s number
and content.
General information
1
Specifications
2
Regular inspection and adjustments
3
Engine
4
Chassis
5
Electrical
6
Tuning
7
78
TUN
90
AB
T
.
R
.
CD
EF
Illustrated symbols 8 to D are used to identify
the specifications appearing in the text.
With engine mounted
8
Special tool
9
Filling fluid
0
Lubricant
A
Tightening
B
Specified value, Service limit
C
Resistance (Ω), Voltage (V), Electric current (A)
D
Illustrated symbols E to H in the exploded
diagrams indicate grade of lubricant and location of lubrication point.
E
GH
B
IJ
M
M
New
Apply engine oil
E
Apply molybdenum disulfide oil
F
Apply lightweight lithium-soap base grease
G
Apply molybdenum disulfide grease
H
Illustrated symbols I to J in the exploded
diagrams indicate where to apply a locking
agent and where to install new parts.
®
Apply locking agent (LOCTITE
I
Use new one
J
)
MEMO
EC090000
INDEX
GENERAL INFORMATION
SPECIFICATIONS
REGULAR INSPECTION AND ADJUSTMENTS
ENGINE
CHASSIS
GEN
INFO
SPEC
INSP
ADJ
ENG
CHAS
1
2
3
4
5
ELECTRICAL
TUNING
–+
ELEC
6
TUN
7
EC0A0000
CONTENTS
CHAPTER 1
GENERAL INFORMATION
DESCRIPTION
MACHINE IDENTIFICATION
IMPORTANT INFORMATION
CHECKING OF CONNECTION
SPECIAL TOOLS
CONTROL FUNCTIONS
FUEL
STARTING AND BREAK-IN
TORQUE-CHECK POINTS
CLEANING AND STORAGE
SEAT, FUEL TANK AND
SIDE COVERS
EXHAUST PIPE AND SILENCER
RADIATOR
CARBURETOR
CAMSHAFTS
CYLINDER HEAD
VALVES AND VALVE SPRINGS
CYLINDER AND PISTON
CLUTCH
OIL FILTER ELEMENT, WATER PUMP
AND RIGHT CRANKCASE COVER
BALANCER
OIL PUMP
KICK SHAFT AND SHIFT SHAFT
AC MAGNETO AND
STARTER CLUTCH
ENGINE REMOVAL
CRANKCASE AND CRANKSHAFT
TRANSMISSION, SHIFT CAM AND
SHIFT FORK
ELECTRICAL COMPONENTS AND
WIRING DIAGRAM
MAP-CONTROLLED CDI UNIT
IGNITION SYSTEM
ELECTRIC STARTING SYSTEM
CHARGING SYSTEM
THROTTLE POSITION SENSOR
SYSTEM
LIGHTING SYSTEM
1 Clutch lever
2 Hot starter lever
3 Engine stop switch
4 Trip meter
5 Main switch
6 Light switch
7 Start switch
8 Front brake lever
9 Throttle grip
0 Radiator cap
A Fuel tank cap
B Taillight
C Kickstarter crank
D Fuel tank
E Headlight
F Radiator
G Coolant drain bolt
H Rear brake pedal
I Valve joint
J Fuel cock
K Cold starter knob
L Air cleaner
M Drive chain
N Shift pedal
O Oil dipstick
P Front fork
GEN
DESCRIPTION
OTE:
• The machine you have purchased may differ
slightly from those shown in the following.
• Designs and specifications are subject to
change without notice.
3
2
1
A
INFO
4
5
6
0
7
8
9
1
B
CD
GH
E
F
P
O
IJ
K
L
MN
1 - 1
1
MACHINE IDENTIFICATION
EC120001
MACHINE IDENTIFICATION
There are two significant reasons for knowing
the serial number of your machine:
1. When ordering parts, you can give the
number to your Yamaha dealer for positive
identification of the model you own.
2. If your machine is stolen, the authorities will
need the number to search for and identify
your machine.
EC121001
VEHICLE IDENTIFICATION NUMBER
The vehicle identification number 1 is
stamped on the right of the steering head pipe.
GEN
INFO
1
1
EC123001
ENGINE SERIAL NUMBER
The engine serial number 1 is stamped into
the elevated part of the right-side of the
engine.
EC124000
MODEL LABEL
The model label 1 is affixed to the frame
under the rider’s seat. This information will be
needed to order spare parts.
1 - 2
IMPORTANT INFORMATION
EC130000
IMPORTANT INFORMATION
EC131010
PREPARATION FOR REMOVAL AND
DISASSEMBLY
1. Remove all dirt, mud, dust, and foreign
material before removal and disassembly.
When washing the machine with high pressured water, cover the parts follows.
• Silencer exhaust port
• Side cover air intake port
• Water pump housing hole at the bottom
• Drain hole on the cylinder head
(right side)
• All electrical components
GEN
INFO
2. Use proper tools and cleaning equipment.
Refer to “SPECIAL TOOLS” section.
3. When disassembling the machine, keep
mated parts together. They include gears,
cylinders, pistons, and other mated parts
that have been “mated” through normal
wear. Mated parts must be reused as an
assembly or replaced.
4. During the machine disassembly, clean all
parts and place them in trays in the order of
disassembly. This will speed up assembly
time and help assure that all parts are correctly reinstalled.
5. Keep away from fire.
1 - 3
IMPORTANT INFORMATION
EC132000
ALL REPLACEMENT PARTS
1. We recommend to use Yamaha genuine
parts for all replacements. Use oil and/or
grease recommended by Yamaha for
assembly and adjustment.
EC133000
GASKETS, OIL SEALS AND O-RINGS
1. All gaskets, oil seals, and O-rings should
be replaced when an engine is overhauled.
All gasket surfaces, oil seal lips, and Orings must be cleaned.
2. Properly oil all mating parts and bearings
during reassembly. Apply grease to the oil
seal lips.
GEN
INFO
EC134000
LOCK WASHERS/PLATES AND COTTER
PINS
1. All lock washers/plates 1 and cotter pins
must be replaced when they are removed.
Lock tab(s) should be bent along the bolt or
nut flat(s) after the bolt or nut has been
properly tightened.
EC135001
BEARINGS AND OIL SEALS
1. Install the bearing(s) 1 and oil seal(s) 2
with their manufacturer’s marks or numbers
facing outward. (In other words, the
stamped letters must be on the side
exposed to view.) When installing oil
seal(s), apply a light coating of lightweight
lithium base grease to the seal lip(s). Oil
the bearings liberally when installing.
CAUTION:
Do not use compressed air to spin the
bearings dry. This causes damage to the
bearing surfaces.
1 - 4
IMPORTANT INFORMATION
EC136000
CIRCLIPS
1. All circlips should be inspected carefully
before reassembly. Always replace piston
pin clips after one use. Replace distorted
circlips. When installing a circlip 1, make
sure that the sharp-edged corner 2 is positioned opposite to the thrust 3 it receives.
See the sectional view.
Shaft
4
GEN
INFO
1 - 5
CHECKING OF CONNECTION
EC1C0001
CHECKING OF CONNECTION
Dealing with stains, rust, moisture, etc. on the
connector.
1. Disconnect:
• Connector
2. Dry each terminal with an air blower.
3. Connect and disconnect the connector two
or three times.
4. Pull the lead to check that it will not come
off.
5. If the terminal comes off, bend up the pin
1 and reinsert the terminal into the connector.
GEN
INFO
6. Connect:
• Connector
OTE:
The two connectors “click” together.
7. Check for continuity with a tester.
OTE:
• If there in no continuity, clean the terminals.
• Be sure to perform the steps 1 to 7 listed
above when checking the wire harness.
• For a field remedy, use a contact revitalizer
available on the market.
• Use the tester on the connector as shown.
1 - 6
GEN
SPECIAL TOOLS
SPECIAL TOOLS
The proper special tools are necessary for complete and accurate tune-up and assembly. Using the
correct special tool will help prevent damage caused by the use of improper tools or improvised
techniques. The shape and part number used for the special tool differ by country, so two types are
provided. Refer to the list provided to avoid errors when placing an order.
OTE:
• For U.S.A. and Canada, use part number starting with “YM-”, “YU-” or “ACC-”.
• For others, use part number starting with “90890-”.
Part numberTool name/How to useIllustration
YU-1135-A, 90890-01135Crankcase separating tool
These tool is used to remove the crankshaft from
either case.
YU-3097, 90890-01252
YU-1256
Dial gauge and stand
Stand
INFO
These tools are used to check each part for runout or
bent.
These tools are used for checking the cooling sys-
tem.
This tool is used when tighten the steering ring nut to
specification.
Use this tool to remove and install the damper rod.
1 - 7
SPECIAL TOOLS
Part numberTool name/How to useIllustration
YM-01442, 90890-01442Fork seal driver
This tool is used when install the fork oil seal.
YU-3112-C, 90890-03112Pocket tester
Use this tool to inspect the coil resistance, output
voltage and amperage.
YU-8036-B
90890-03113
YM-33277-A, 90890-03141 Timing light
Inductive tachometer
Engine tachometer
This tool is needed for observing engine rpm.
GEN
INFO
This tool is necessary for checking ignition timing.
YM-4019, 90890-04019Valve spring compressor
This tool is needed to remove and install the valve
assemblies.
YM-91042, 90890-04086Clutch holding tool
This tool is used to hold the clutch when removing or
installing the clutch boss securing nut.
YM-4111, 90890-04111
YM-4116, 90890-04116
YM-4112, 90890-04112
YM-4117, 90890-04117
YM-4113, 90890-04113
YM-4118, 90890-04118
Valve guide remover
Intake 4.0 mm (0.16 in)
Exhaust 4.5 mm (0.18 in)
This tool is needed to remove and install the valve
guide.
Valve guide installer
Intake 4.0 mm (0.16 in)
Exhaust 4.5 mm (0.18 in)
This tool is needed to install the valve guide.
Valve guide reamer
Intake 4.0 mm (0.16 in)
Exhaust 4.5 mm (0.18 in)
This tool is needed to rebore the new valve guide.
1 - 8
SPECIAL TOOLS
Part numberTool name/How to useIllustration
YM-04141, 90890-04141Rotor puller
This tool is used to remove the flywheel magneto.
YM-34487
90890-06754
ACC-QUICK-GS-KT
90890-85505
Dynamic spark tester
Ignition checker
This instrument is necessary for checking the ignition
system components.
Quick gasket
YAMAHA Bond No. 1215
This sealant (Bond) is used for crankcase mating sur-
face, etc.
GEN
INFO
1 - 9
CONTROL FUNCTIONS
EC150000
CONTROL FUNCTIONS
MAIN SWITCH
Functions of the respective switch positions
are as follows:
ON:
The engine can be started only at this position.
OFF:
All electrical circuits are switched off.
Main switch indicator light
The main switch 1 is equipped with an indicator light 2 to avoid forgetting to turn it off. This
light functions as follows.
• It lights up with the main switch “ON”.
• It goes out when the engine increases its
speed after being started.
• It lights up again when the engine is stopped.
GEN
INFO
OTE:
If the indicator light will not light up with the
main switch “ON”, it shows a lack of the battery
voltage. Recharge the battery. If the engine is
kick started, turn off the light switch.
ENGINE STOP SWITCH
The engine stop switch 1 is located on the left
handlebar. Continue pushing the engine stop
switch till the engine comes to a stop.
START SWITCH
The start switch 1 is located on the right handlebar. Push this switch to crank the engine
with the starter.
1 - 10
CONTROL FUNCTIONS
EC152000
CLUTCH LEVER
The clutch lever 1 is located on the left handlebar; it disengages or engages the clutch.
Pull the clutch lever to the handlebar to disengage the clutch, and release the lever to
engage the clutch. The lever should be pulled
rapidly and released slowly for smooth starts.
EC153000
SHIFT PEDAL
The gear ratios of the constant-mesh 5 speed
transmission are ideally spaced. The gears
can be shifted by using the shift pedal 1 on
the left side of the engine.
GEN
INFO
1
KICKSTARTER CRANK
Rotate the kickstarter crank 1 away from the
engine. Push the starter down lightly with your
foot until the gears engage, then kick smoothly
and forcefully to start the engine. This model
has a primary kickstarter crank so the engine
can be started in any gear if the clutch is disengaged. In normal practices, however, shift to
neutral before starting.
EC155001
THROTTLE GRIP
The throttle grip 1 is located on the right handlebar; it accelerates or decelerates the
engine. For acceleration, turn the grip toward
you; for deceleration, turn it away from you.
EC156000
FRONT BRAKE LEVER
The front brake lever 1 is located on the right
handlebar. Pull it toward the handlebar to activate the front brake.
1 - 11
CONTROL FUNCTIONS
EC157000
REAR BRAKE PEDAL
The rear brake pedal 1 is located on the right
side of the machine. Press down on the brake
pedal to activate the rear brake.
FUEL COCK
The fuel cock supplies fuel from the tank to
carburetor and also filters the fuel. The fuel
cock has three positions:
OFF:With the lever in this position, fuel will not
flow. Always return the lever to this position when the engine is not running.
ON: With the lever in this position fuel flows to
the carburetor. Normal riding is done with
the lever in this position.
RES:With the lever in this position fuel flows to
the carburetor from the reserve section of
the fuel tank after the main supply of the
fuel has been depleted. Normal riding is
possible with the lever is in this position,
but it is recommended to add fuel as
soon as possible.
GEN
INFO
COLD STARTER KNOB
When cold, the engine requires a richer air-fuel
mixture for starting. A separate starter circuit,
which is controlled by the cold starter knob 1,
supplies this mixture. Pull the cold starter knob
out to open the circuit for starting. When the
engine has warmed up, push it in to close the
circuit.
HOT STARTER LEVER
The hot starter lever 1 is used when starting a
warm engine.
Use the hot starter lever when starting the
engine again immediately after it was stopped
(the engine is still warm). Pulling the hot starter
lever injects secondary air to thin the air-fuel
mixture temporarily, allowing the engine to be
started more easily.
1 - 12
CONTROL FUNCTIONS
LIGHT SWITCH
The light switch 1 is located on the handlebar.
EC15F000
VALVE JOINT
This valve joint 1 prevents fuel from flowing
out and is installed to the fuel tank breather
hose.
CAUTION:
In this installation, make sure the arrow
faces the fuel tank and also downward.
GEN
INFO
1
SPARK PLUG WRENCH
This spark plug wrench 1 is used to remove
and install the spark plug.
1
NIPPLE WRENCH
This nipple wrench 1 is used to tighten the
spoke.
1 - 13
GEN
FUEL
FUEL
Always use the recommended fuel as stated
below. Also, be sure to use new gasoline the
day of a race.
Recommended fuel:
Except for ZA:
Premium unleaded gasoline
only with a research octane
number of 95 or higher.
For ZA:
Premium gasoline
CAUTION:
Use only unleaded gasoline. The use of
leaded gasoline will cause severe damage
to the engine internal parts such as valves,
piston rings, and exhaust system, etc.
INFO
OTE:
If knocking or pinging occurs, use a different
brand of gasoline or higher octane grade.
WARNING
• For refueling, be sure to stop the engine
and use enough care not to spill any fuel.
Also be sure to avoid refueling close to a
fire.
• Refuel after the engine, exhaust pipe, etc.
have cooled off.
1 - 14
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