ECU YAMAHA WR 250F 2008 Owners Manual

TO THE NEW OWNER
This manual will provide you with a
good basic understanding of fea-
tures, operation, and basic mainte-
nance and inspection items of this
machine. Please read this manual
carefully and completely before oper-
ating your new machine. If you have
any questions regarding the opera-
tion or maintenance of your machine,
please consult your Yamaha dealer.
This manual should be considered a
permanent part of this machine and
should remain with it even if the ma-
chine is subsequently sold.
NOTICE
Some data in this manual may be-
come outdated due to improve-
ments 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.
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.
HOW TO USE THIS MANUAL
FINDING THE REQUIRED PAGE
1. This manual consists of seven chapters; "General Information",
"Specifications", "Regular inspec-
tion and adjustments", "Tuning",
"Engine", "Chassis" and "Electri-
cal". 2. The table of contents is at the be-
ginning of the manual. Look over
the general layout of the book be-
fore 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 de-
scription.
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 me-
chanic with an easy to read, handy
reference that contains comprehen-
sive explanations of all disassembly,
repair, assembly, and inspection op-
erations.
In this revised format, the condition of
a faulty component will precede an
arrow symbol and the course of ac-
tion required will follow the symbol,
e.g., •BearingsPitting/damage →Replace.
10. PROPERLY SECURE THE
MACHINE BEFORE TRANS-
PORTING IT.
When transporting the ma-
chine in another vehicle, al-
ways be sure it is properly
secured and in an upright po-
sition and that the fuel cock is
in the "OFF" position. Other-
wise, fuel may leak out of the
carburetor or fuel tank.

1-5
SPECIAL TOOLS
Steering nut wrench
YU-33975, 90890-01403 This tool is used when tighten the
steering ring nut to specification.
Damper rod holder
YM-01494, 90890-01494 Use this tool to remove and install
the damper rod.
Fork seal driver
YM-A0948, 90890-01502 This tool is used when install the fork
oil seal.
Sheave holder
YS-1880-A, 90890-01701 This tool is used for when loosening
or tightening the flywheel magneto
securing nut.
Pocket tester
YU-3112-C, 90890-03112 Use this tool to inspect the coil resis-
tance, output voltage and amper-
age.
Timing light
YM-33277-A, 90890-03141 This tool is necessary for checking
ignition timing.
Tool name/Part number How to use Illustration

1-6
SPECIAL TOOLS
Valve spring compressor
YM-4019, 90890-04019 This tool is needed to remove and
install the valve assemblies.
Clutch holding tool
YM-91042, 90890-04086 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)
YM-4111, 90890-04111
YM-4116, 90890-04116 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)
YM-4112, 90890-04112
YM-4117, 90890-04117 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)
YM-4113, 90890-04113
YM-4118, 90890-04118 This tool is needed to rebore the
new valve guide.
Rotor puller
YM-04141, 90890-04141 This tool is used to remove the fly-
wheel magneto.
Dynamic spark tester
YM-34487
Ignition checker
90890-06754 This instrument is necessary for
checking the ignition system compo-
nents.
Tool name/Part number
How to useIllustration

1-17
CLEANING AND STORAGE
CLEANING AND STORAGE
CLEANING
Frequent cleaning of your machine
will enhance its appearance, maintain
good overall performance, and ex-
tend the life of many components.
1. Before washing the machine, block off the end of the exhaust
pipe to prevent water from enter-
ing. A plastic bag secured with a
rubber band may be used for this
purpose.
2. If the engine is excessively greasy, apply some degreaser to
it with a paint brush. Do not apply
degreaser to the chain, sprockets,
or wheel axles.
3. Rinse the dirt and degreaser off with a garden hose; use only
enough pressure to do the job.
Excessive hose pressure may
cause water seepage and contami-
nation of wheel bearings, front
forks, brakes and transmission
seals. Many expensive repair bills
have resulted from improper high
pressure detergent applications
such as those available in coin-op-
erated car washers.
4. After the majority of the dirt has been hosed off, wash all surfaces
with warm water and a mild deter-
gent. Use an old toothbrush to
clean hard-to-reach places.
5. Rinse the machine off immediate- ly with clean water, and dry all
surfaces with a soft towel or cloth.
6. Immediately after washing, re- move excess water from the
chain with a paper towel and lubri-
cate the chain to prevent rust.
7. Clean the seat with a vinyl uphol- stery cleaner to keep the cover
pliable and glossy.
8. Automotive wax may be applied to all painted or chromed surfac-
es. Avoid combination cleaner-
waxes, as they may contain abra-
sives.
9. After completing the above, start the engine and allow it to idle for
several minutes. STORAGE
If your machine is to be stored for 60
days or more, some preventive mea-
sures must be taken to avoid deterio-
ration. After cleaning the machine
thoroughly, prepare it for storage as
follows:
1. Drain the fuel tank, fuel lines, and
the carburetor float bowl.
2. Remove the spark plug, pour a ta-
blespoon of SAE 10W-30 motor
oil in the spark plug hole, and re-
install the plug. With the engine
stop switch pushed in, kick the en-
gine over several times to coat the
cylinder walls with oil.
3. Remove the drive chain, clean it thoroughly with solvent, and lubri-
cate it. Reinstall the chain or store
it in a plastic bag tied to the frame.
4. Lubricate all control cables.
5. Block the frame up to raise the
wheels off the ground.
6. Tie a plastic bag over the exhaust pipe outlet to prevent moisture
from entering.
7. If the machine is to be stored in a humid or salt-air environment,
coat all exposed metal surfaces
with a film of light oil. Do not apply
oil to rubber parts or the seat cov-
er.
Make any necessary repairs before
the machine is stored.

2-22
CABLE ROUTING DIAGRAM
A. Insert the end of the fuel tank breather hose into the hole in
the steering stem.
B. Fasten the throttle cable, hot
starter cable and rectifier/regula-
tor lead onto the frame. Locate
the clamp end facing the lower
side of the hot starter cable and
cut off the tie end.
C. Fasten the diode (at the mark-
ing), throttle cable and hot start-
er cable onto the frame. Locate
the clamp end facing toward the
lower right of the frame and with
the tie end facing downward.
D. Fasten the wire harness, throttle
position sensor lead, starter mo-
tor lead and negative battery
lead onto the frame. Pass the
clamp through the hole in the
stay (air cut-off valve). Locate
the clamp end facing toward the
lower side of the frame and cut
off the tie end.
E. Fasten the throttle position sen-
sor lead onto the frame. Locate
the clamp end facing toward the
lower side of the frame and cut
off the tie end.
F. Pass the carburetor breather hoses, carburetor overflow hose
and catch tank breather hose
between the connecting rod and
cross tube (frame).
G. Fasten the neutral switch lead and oil hose together with the
plastic locking ties and cut off
the tie ends.
H. Fasten the neutral switch lead
and AC magneto lead onto the
frame. Locate the clamp end
facing toward the outside of the
frame and tie end facing toward
the rear of the frame.
I. Pass the clutch cable through
the cable guide.
J. Fasten the starter motor lead, AC magneto lead and neutral
switch lead onto the frame. Lo-
cate the clamp end facing to-
ward the rear of the frame and
cut off the tie end.
K. Fasten the clutch cable, starter motor lead, negative battery
lead, AC magneto lead and neu-
tral switch lead onto the frame.
Locate the clamp end facing to-
ward the rear of the frame and
cut off the tie end.
L. Pass the neutral switch lead and
AC magneto lead on the inside
of the wire harness. M. Fasten the clutch cable, AC
magneto lead and neutral switch
lead onto the frame. Locate the
clamp end near the clutch cable
and cut off the tie end.
N. Pass the clutch cable and wire harness through the cable
guide.
O. Locate the couplers in the frame recess.
P. Pass the carburetor breather hoses, carburetor overflow hose
and catch tank breather hose so
that the hoses do not contact the
rear shock absorber.
Q. Secure the coupler by pushing it
into the hole in the headlight
unit.

2-26
CABLE ROUTING DIAGRAM
C. Pass the starter motor lead through the hole in the relay
holder.
D. Fit the cover securely.
E. Connect the wire harness to the starter relay.
F. Fasten the catch tank breather
hose and catch tank hose to the
rear frame. Clamp them close to
where they are joined to the
frame. Fasten the pipe tightly
enough not to crush it. Locate
the clamp end facing toward the
rear of the frame with the tie end
facing downward.
G. Fasten the (three) CDI unit leads
and taillight lead to the rear
frame. Locate the clamp end
facing toward the upper side of
the frame and cut off the tie end.
H. Connect the negative battery lead to the battery negative ter-
minal.
I. Connect the negative battery lead to the wire harness.
J. Fasten the wire harness to the rear frame. Locate the clamp
end facing toward the upper side
of the frame and the tie end to-
ward the inside of the frame.
Clamp the wire harness at the
marking.
K. Pass the wire harness, starter relay lead, starting circuit cut-off
relay lead and negative battery
lead through the hole in the relay
holder.
L. Fasten the (three) CDI unit leads and taillight lead to the rear
frame. Locate the clamp end
facing toward the lower side of
the frame and cut off the tie end.
M. Fasten the taillight lead to the rear frame. Locate the clamp
end facing toward the upper side
of the frame and cut off the tie
end.
N. Do not allow the taillight lead to
slacken.
O. Locate the CDI unit lead be- tween the CDI unit and rear
fender.
P. Locate the CDI unit coupler in the clearance between the up-
per side of the CDI unit and low-
er side of the catch tank stay.
Q. Locate the CDI unit lead be-
tween the CDI unit and rear
frame.

2-27
CABLE ROUTING DIAGRAM
1. Throttle cable
2. Clamp
3. Brake hose
4. Clutch cable
5. Hose guide
6. Main switch coupler
7. Wire harness
8. Headlight coupler
9. Hot starter cable
10. Multi-function display bracket
11. Main switch12. Upper bracket
13. Clutch switch coupler
14. Engine stop switch coupler
15. Multi-function display coupler
16. Start switch coupler
17. Speed sensor coupler
18. Speed sensor lead
A. Fasten the star
t switch lead to
the handlebar with the plastic
bands. B. Fasten the engine stop switch
lead and clutch switch lead to
the handlebar with the plastic
bands.
C. Pass the brake hose through
the hose guides.
D. Secure the coupler by inserting it into the multi-function display
bracket.

2-28
CABLE ROUTING DIAGRAM
E. Pass the throttle cables, clutch cable and hot starter cable be-
tween the upper bracket and
multi-function display bracket.
F. Fasten the multi-function display leads to the bracket. Cut off the
tie end.
G. Secure the coupler by pushing it into the hole in the multi-function
display bracket.
H. Secure the wire harness clip by pushing it into the hole in the
multi-function display bracket on
the inside.
I. Fasten the wire harness to the multi-function display bracket.
Cut off the tie end.
J. Fasten the main switch lead (wire harness side) to the multi-
function display br acket. Locate
the clamp end facing toward the
lower side of the frame and cut
off the tie end.
K. Pass the speed sensor lead through the guide on the outside
of the front fork.

5-24
VALVES AND VALVE SPRINGS
2. Measure:• Compressed spring force "a"
Out of specification →Replace.
b. Installed length
3. Measure: • Spring tilt "a"
Out of specification →Replace.
CHECKING THE VALVE LIFTERS
1. Inspect: • Valve lifterScratches/damage →Replace
both lifters and cylinder head. INSTALLING THE VALVES
1. Apply:
• Molybdenum disulfide oilOnto the valve stem and valve
stem seal.
2. Install: • Valve "1"
• Valve spring seat "2"
• Valve stem seal "3"
• Valve spring "4"
• Valve spring retainer "5"To cylinder head.
• Make sure that each valve is in-stalled in its original place, also re-
ferring to the painted color as
follows.
Intake (middle) "a": Orange
Intake (right/left) "b": Green
Exhaust "c": Purple
• Install the valve springs with the
larger pitch "d" facing upward.
e. Smaller pitch
3. Install:
• Valve cotter
While compressing the valve spring
with a valve spring compressor "1" in-
stall the valve cotters.
4. To secure the va lve cotters onto
the valve stem, lightly tap the
valve tip with a piece of wood.
Hitting the valve tip with excessive
force could damage the valve.
5. Install: • Adjusting pad "1"
• Valve lifter "2"
• Apply the molybdenum disulfide oil
on the valve stem end.
• Apply the engine oil on the valve lift- ers.
• Valve lifter must turn smoothly when rotated with a finger.
• Be careful to reinstall valve lifters and pads in their original place.
Compressed spring
force: Intake:
103–118 N at 29.13
mm (10.50–12.09 kg at
29.13 mm, 23.15–
26.66 lb at 1.15 in)
Exhaust: 126–144 N at 29.30
mm (12.85–14.68 kg at
29.30 mm, 28.32–
32.37 lb at 1.15 in)
Spring tilt limit: Intake:2.5°/1.6 mm (0.063 in)
Exhaust: 2.5°/1.6 mm (0.063 in)
Valve spring compres-
sor:
YM-4019/90890-04019

5-55
ENGINE REMOVAL
HANDLING NOTE
Support the machine securely so
there is no danger of it falling over.
REMOVING THE DRIVE
SPROCKET
1. Remove:• Nut (drive sprocket) "1"
• Lock washer "2"
• Straighten the lock washer tab.
• Loosen the nut while applying the rear brake.
2. Remove:• Drive sprocket "1"
• Drive chain "2"
Remove the drive sprocket together
with the drive chain.
REMOVING THE ENGINE
1. Remove:• Pivot shaft "1"
If the pivot shaft is pulled all the way
out, the swingarm will come loose. If
possible, insert a sh aft of similar di-
ameter into the other side of the swin-
garm to support it.
2. Remove:
• Engine "1"From right side.
Make sure that the couplers, hoses
and cables are disconnected.
INSTALLING THE ENGINE
1. Install:
• Engine "1"Install the engine from right side.
• Pivot shaft "2"
• Engine mounting bolt (lower) "3"
• Lower engine bracket "4"
• Bolt (lower engine bracket) "5"
• Patch "6"
• Engine mounting bolt (front) "7"
• Upper engine bracket "8"
• Bolt (upper engine bracket) "9"
• Engine mounting bolt (upper) "10"
• Lower engine guard "11"
• Bolt (lower engine guard) "12"
• Apply the molybdenum disulfide grease on the pivot shaft.
• Install the patch with the claw "a"
facing outside the chassis.
INSTALLING THE BRAKE PEDAL
1. Install:• Spring "1"
• Brake pedal "2"
• O-ring "3"
• Bolt (brake pedal) "4"
• Clip "5"
Apply the lithium soap base grease
on the bolt, O-rings and brake pedal
bracket.
INSTALLING THE DRIVE
SPROCKET
1. Install:• Drive sprocket "1"
• Drive chain "2"
Install the drive sprocket together
with the drive chain.
Pivot shaft:
85 Nm (8.5 m•kg, 61
ft•lb)
Engine mounting bolt
(lower): 53Nm (5.3 m•kg, 38
ft•lb)
Bolt (lower engine brack-
et): 34 Nm (3.4 m•kg, 24
ft•lb)
Engine mounting bolt
(front): 53 Nm (5.3 m•kg, 38
ft•lb)
Bolt (upper engine brack-
et): 34 Nm (3.4 m•kg, 24
ft•lb)
Engine mounting bolt
(upper): 55 Nm (5.5 m•kg, 40
ft•lb)
Bolt (lower engine
guard): 7 Nm (0.7 m•kg, 5.1
ft•lb)
Bolt (brake pedal): 26 Nm (2.6 m•kg, 19
ft•lb)