Congratulations on your purchase of a
Yamaha YZ 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.
NOTE:
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some data in this manual may become outdated.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 properly 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.
NOTE:
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
HOW TO USE
THIS MANUAL
EC081000
PARTICULARLY IMPORTANT
INFORMATION
The Safety Alert Symbol means ATTENTION!
BECOME ALERT! YOUR SAFETY IS
INVOLVED!
WARNING
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
“Tuning”.
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 unnecessary removal job.
6. For jobs requiring more information, the step-by-step format supplements 6 are given in addition to the exploded diagram and job instruction chart.
1
2
3
4
5
6
7
8
9
0
A
B
C
D
E
F
G
H
I
)
12
GEN
INFO
34
SPEC
INSP
ADJ
56
CHAS
78
ENG
–+
ELEC
TUN
90
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
Specifications
Regular inspection and adjustments
Engine
Chassis
Electrical
Tuning
Illustrated symbols 8 to D are used to identify
the specifications appearing in the text.
With engine mounted
Special tool
Filling fluid
Lubricant
Tightening
Specified value, Service limit
Resistance (Ω), Voltage (V), Electric current (A)
AB
T
.
R
.
CD
EF
E
GH
B
IJ
M
M
Illustrated symbols E to H in the exploded
diagrams indicate grade of lubricant and location of lubrication point.
1 Clutch lever
2 Hot starter lever
3 Front brake lever
4 Throttle grip
5 Radiator cap
6 Fuel tank cap
7 Engine stop switch
8 Kickstarter crank
9 Fuel tank
0 Radiator
A Coolant drain bolt
B Rear brake pedal
C Valve joint
D Fuel cock
E Cold starter knob
F Drive chain
G Air filter
H Shift pedal
I Dipstick
J Front fork
GEN
DESCRIPTION
NOTE:
● The machine you have purchased may differ
slightly from those shown in the following.
● Designs and specifications are subject to
change without notice.
INFO
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
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)
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.
1 - 3
5. Keep away from fire.
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 O-rings 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.
4 Shaft
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
NOTE:
The two connectors “click” together.
7. Check for continuity with a tester.
NOTE:
● If there in no continuity, clean the terminals.
● Be sure to perform the steps 1 to 7 listed
above when checking the wireharness.
● 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.
NOTE:
● 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.
YM-1189, 90890-01189Flywheel puller
YU-1135-A90890-01135
YM-118990890-01189
INFO
This tool is used to remove the flywheel magneto.
YU-1235, 90890-01235Rotor holding tool
This tool is used when loosening or tightening the flywheel magneto securing nut.
These tools are used to check each part for runout or
bent.
Crankshaft installing tool
Crankshaft installing pot
Crankshaft installing bolt
Spacer (crankshaft installer)
Adapter (M12)
These tools are used to install the crankshaft.
This tool is used to remove the piston pin.
Radiator cap tester
Radiator cap tester adapter
YU-123590890-01235
YU-3097
YU-1256
YU-90050
YU-90063
YU-91044
YU-130490890-01304
YU-24460-01
YU-33984
90890-01252
90890-01274
90890-01275
90890-01278
90890-04081
90890-01325
90890-01352
These tools are used for checking the cooling system.
1 - 7
SPECIAL TOOLS
Part numberTool name/How to useIllustration
YU-33975, 90890-01403Steering nut wrench
This tool is used when tighten the steering ring nut to
specification.
YM-1423, 90890-01423Damper rod holder
Use this tool to remove and install the damper rod.
YM-01442, 90890-01442Fork seal driver
This tool is used when install the fork oil seal.
YU-3112-C, 90890-03112Pocket tester
YU-3397590890-01403
YM-142390890-01423
YM-0144290890-01442
YU-3112-C90890-03112
GEN
INFO
Use this tool to inspect the coil resistance, output
voltage and amperage.
YU-8036-B
90890-03113
YM-33277-A, 90890-03141 Timing light
YM-4019, 90890-04019Valve spring compressor
YM-91042, 90890-04086Clutch holding tool
YM-4111, 90890-04111
YM-4116, 90890-04116
Inductive tachometer
Engine tachometer
This tool is needed for observing engine rpm.
This tool is necessary for checking ignition timing.
This tool is needed to remove and install the valve
assemblies.
This tool is used to hold the clutch when removing or
installing the clutch boss securing nut.
Valve guide remover
Intake 4.0 mm (0.16 in)
Exhaust 4.5 mm (0.18 in)
YU-8036-B90890-03113
YM-33277-A90890-03141
YM-401990890-04019
YM-9104290890-04086
YM-4111
YM-4116
90890-04111
90890-04116
This tool is needed to remove and install the valve
guide.
1 - 8
SPECIAL TOOLS
Part numberTool name/How to useIllustration
YM-4112, 90890-04112
YM-4117, 90890-04117
YM-4113, 90890-04113
YM-4118, 90890-04118
YM-34487
90890-06754
ACC-QUICK-GS-KT
90890-85505
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.
Dynamic spark tester
Ignition checker
This instrument is necessary for checking the ignition
system components.
Quick gasket
YAMAHA Bond No. 1215
YM-4112
YM-4117
YM-4113
YM-4118
YM-3448790890-06754
ACC-QUICK-GS-KT90890-85505
GEN
INFO
90890-04112
90890-04117
90890-04113
90890-04118
This sealant (Bond) is used for crankcase mating
surface, etc.
1 - 9
CONTROL FUNCTIONS
EC150000
CONTROL FUNCTIONS
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.
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.
GEN
INFO
1
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.
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.
1 - 10
CONTROL FUNCTIONS
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.
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.
GEN
INFO
EC158001
FUEL COCK
The fuel cock supplies fuel from the tank to
carburetor while filtering the fuel. The fuel cock
has the two 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.
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 - 11
CONTROL FUNCTIONS
EC15R001
DETACHABLE SIDESTAND
This sidestand 1 is used to support only the
machine when standing or transporting it.
WARNING
● Never apply additional force to the side-
stand.
● Remove this sidestand before starting
out.
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 - 12
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
NOTE:
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 - 13
STARTING AND BREAK-IN
STARTING AND BREAK-IN
WARNING
Never start or run the engine in a closed
area. The exhaust fumes are poisonous;
they can cause loss of consciousness and
death in a very short time. Always operate
the machine in a well-ventilated area.
CAUTION:
● The carburetor on this machine has a
built-in accelerator pump. Therefore,
when starting the engine, do not operate
the throttle or the spark plug will foul.
● Unlike a two-stroke engine, this engine
cannot be kick started when the throttle is
open because the kick starter may kick
back. Also, if the throttle is open the air/
fuel mixture may be too lean for the
engine to start.
● Before starting the machine, perform the
checks in the pre-operation check list.
GEN
INFO
STARTING A COLD ENGINE
1. Inspect the coolant level.
2. Turn the fuel cock to “ON”.
3. Shift the transmission into neutral.
4. Fully open the cold starter knob 1.
5. Kick the kickstarter crank.
WARNING
Do not open the throttle while kicking the
kickstarter crank. Otherwise, the kickstarter may kick back.
1 - 14
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