2009 YAMAHA WR 450F engine

4-5
CHASSIS
CHASSIS
SELECTION OF THE SECONDARY
REDUCTION RATIO (SPROCKET)
ondary gear reduction ratio>
• It is generally said that the second-
ary gear ratio should be reduced for
a longer straight portion of a speed
course and should be increased for
a course with many corners. Actual-
ly, however, as the speed depends
on the ground condition of the day
of the ride, be sure to run through
the circuit to set the machine suit-
able for the entire course.
• In actuality, it is very difficult to
achieve settings suitable for the en-
tire course and some settings may
be sacrificed. Thus, the settings
should be matched to the portion of
the course that has the greatest ef-
fect on the ride result. In such a
case, run through the entire course
while making notes of lap times to
find the best balance; then, deter-
mine the secondary reduction ratio.
• If a course has a long straight por-
tion where a machine can run at
maximum speed, the machine is
generally set such that it can devel-
op its maximum revolutions toward
the end of the straight line, with care
taken to avoid the engine over-rev-
ving.
Riding technique varies from rider to
rider and the performance of a ma-
chine also vary from machine to ma-
chine. Therefore, do not imitate other
rider's settings from the beginning but
choose your own setting according to
the level of your riding technique.
DRIVE AND REAR WHEEL
SPROCKETS SETTING PARTSTIRE PRESSURE
Tire pressure should be adjust to suit
the road surface condition of the cir-
cuit.
• Under a rainy, muddy, sandy, or
slippery condition, the tire pressure
should be lower for a larger area of
contact with the road surface.
• Under a stony or hard road condi-
tion, the tire pressure should be
higher to prevent a flat tire.
FRONT FORK SETTING
The front fork setting should be made
depending on the rider's feeling of an
actual run and the circuit conditions.
The front fork setting includes the fol-
lowing three factors:
1. Setting of air spring characteris-
tics
• Change the fork oil level.
2. Setting of spring preload
• Change the spring.
• Install the adjustment washer.
3. Setting of damping force
• Change the compression damp-
ing.
• Change the rebound damping.
The spring acts on the load and
the damping force acts on the
cushion travel speed.
CHANGE IN LEVEL AND
CHARACTERISTICS OF FORK OIL
Damping characteristic near the final
stroke can be changed by changing
the fork oil amount.
Adjust the oil level in 5 mm (0.2 in)
increments or decrements. Too
low oil level causes the front fork
to produce a noise at full rebound
or the rider to feel some pressure
on his hands or body. Alternative-
ly, too high oil level will develop
unexpectedly early oil lock with
the consequent shorter front fork
travel and deteriorated perfor-
mance and characteristics. There-
fore, adjust the front fork within
the specified range.
Secondary reduction ratio =
Number of rear wheel sprocket
teeth/Number of drive sprocket
teeth
Standard secondary
reduction ratio50/13
(3.846)
* 47/14
(3.357)
* For EUROPE
Part
nameSize Part number
Drive
sprocket
"1"
*(STD) *13T 9383E-13233
(STD) 13T 5TJ-17460-00
* 14T 9383E-14215
** (STD) ** 14T 5NG-17460-00
* For AUS and NZ
** For EUROPE
Part
nameSize Part number
Rear
wheel
sprocket
"2"
** (STD) ** 47T 1C3-25447-00
48T 5GS-25448-50
* 48T 1C3-25448-00
* 49T 1C3-25449-00
(STD) 50T 5TJ-25450-80
* (STD) * 50T 1C3-25450-00
* 51T 1C3-25451-00
52T 5TJ-25452-80
* 52T 1C3-25452-00
* For AUS and NZ
** For EUROPE
Standard tire pressure:
100 kPa (1.0 kgf/cm2,
15 psi)
Extent of adjustment:
60–80 kPa (0.6–0.8 kgf/
cm
2, 9.0–12 psi)
Extent of adjustment:
100–120 kPa (1.0–1.2
kgf/cm
2, 15–18 psi)

4-7
CHASSIS
CHOOSING SET LENGTH
1. Place a stand or block under the
engine to put the rear wheel
above the floor, and measure the
length "a" between the rear wheel
axle center and the rear fender
holding bolt.
2. Remove the stand or block from
the engine and with a rider astride
the seat, measure the sunken
length "b" between the rear wheel
axle center and the rear fender
holding bolt.
3. Loosen the locknut "1" and make
adjustment by turning the spring
adjuster "2" to achieve the stan-
dard figure from the subtraction of
the length "b" from the length "a".
• If the machine is new and after it is
broken in, the same set length of
the spring may change because of
the initial fatigue, etc. of the spring.
Therefore, be sure to make reeval-
uation.
• If the standard figure cannot be
achieved by adjusting the spring
adjuster and changing the spring
set length, replace the spring with
an optional one and make re-ad-
justment.
SETTING OF SPRING AFTER
REPLACEMENT
After replacement, be sure to adjust
the spring to the set length [sunken
length 90–100 mm (3.5–3.9 in)] and
set it.
1. Use of soft spring
• Set the soft spring for less re-
bound damping to compensate
for its less spring load. Run with
the rebound damping adjuster
one or two clicks on the softer
side and readjust it to suit your
preference.
2. Use of stiff spring
• Set the soft spring for more re-
bound damping to compensate
for its greater spring load. Run
with the rebound damping adjust-
er one or two clicks on the stiffer
side and readjust it to suit your
preference.
Adjusting the rebound damping will
be followed more or less by a change
in the compression damping. For cor-
rection, turn the low compression
damping adjuster on the softer side.
When using a rear shock absorber
other than currently installed, use
the one whose overall length "a"
does not exceed the standard as it
may result in faulty performance.
Never use one whose overall
length is greater than standard.
REAR SHOCK ABSORBER
SETTING PARTS
• Rear shock spring "1"
• The I.D. mark "a" is marked at the
end of the spring.
• Spring specification varies accord-
ing to the color and quantity of I.D.
marks.
• Extent of adjustment (spring pre-
load)
For the spring preload adjustment, re-
fer to "ADJUSTING THE REAR
SHOCK ABSORBER SPRING PRE-
LOAD" in the CHAPTER 3.
Standard figure:
90–100 mm (3.5–3.9 in)
Length "a" of standard
shock:
488.5 mm (19.23 in)
TYPESPRI
NG
RAT
ESPRING
PART
NUM-
BER
(-22212-)I.D.
MARK/
Q'TY
SOFT 4.3 5UN-00 Brown/1
4.5 5UN-10 Green/1
4.7 5UN-20 Red/1
4.9 5UN-30 Black/1
5.1 5UN-40 Blue/1
5.3 5UN-50 Yellow/1
STD 5.5 5UN-60 Pink/1
STIFF5.7 5UN-70 White/1
Maximum Minimum
Position in
which the
spring is turned
in 13 mm (0.51
in) from its free
length.Position in
which the
spring is turned
in 1.5 mm (0.06
in) from its free
length.

5-1
RADIATOR
ENGINE
This section is intended for those who have basic knowledge and skill concerning the servicing of Yamaha motorcycles
(e.g., Yamaha dealers, service engineers, etc.) Those who have little knowledge and skill concerning servicing are request-
ed not to undertake inspection, adjustment, disassembly, or reassembly only by reference to this manual. It may lead to
servicing trouble and mechanical damage.
RADIATOR
REMOVING THE RADIATOR
Order Part name Q'ty Remarks
Drain the coolant.Refer to "CHANGING THE COOLANT" sec-
tion in the CHAPTER 3.
Seat, fuel tank and left side coverRefer to "REMOVING THE SEAT, FUEL
TANK AND SIDE COVERS" section in the
CHAPTER 3.
Exhaust pipeRefer to "REMOVING THE EXHAUST PIPE
AND SILENCER" section in the CHAPTER 3.
1 Radiator guard 2
2 Radiator hose clamp 8
3 Right radiator 1
4 Radiator hose 2 1
5 Radiator hose 3 1
5

5-3
RADIATOR
HANDLING NOTE
Do not remove the radiator cap
when the engine and radiator are
hot. Scalding hot fluid and steam
may be blown out under pressure,
which could cause serious injury.
When the engine has cooled, open
the radiator cap by the following
procedure:
Place a thick rag, like a towel, over
the radiator cap, slowly rotate the
cap counterclockwise to the de-
tent. This procedure allows any re-
sidual pressure to escape. When
the hissing sound has stopped,
press down on the cap while turn-
ing counterclockwise and remove
it.
CHECKING THE RADIATOR
1. Inspect:
• Radiator core "1"
Obstruction→Blow out with com-
pressed air through rear of the ra-
diator.
Bent fin→Repair/replace.
INSTALLING THE RADIATOR
1. Install:
• Pipe 1 "1"
• Radiator hose 1 "2"
• Pipe 2 "3"
• Radiator hose 3 "4"
• Radiator hose 4 "5"2. Install:
• Radiator hose 2 "1"
• Left radiator "2"
3. Install:
• Catch tank hose "1"
• Right radiator "2"
Refer to "CABLE ROUTING DIA-
GRAM" section in the CHAPTER
2.
4. Install:
• Radiator guard "1"
First fit the inner hook portion "a" and
then the outer one "b" onto the radia-
tor.
5. Install:
• Catch tank "1"
• Bolt (catch tank) "2"
• Bolt (catch tank) "3"
• Catch tank hose "4"
• Catch tank breather hose "5"
Refer to "CABLE ROUTING DIA-
GRAM" section in the CHAPTER
2.
Pipe 1:
10 Nm (1.0 m•kg, 7.2
ft•lb)
Radiator hose 1:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Pipe 2:
10 Nm (1.0 m•kg, 7.2
ft•lb)
Radiator hose 3:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Radiator hose 4:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Radiator hose 2:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Left radiator:
10 Nm (1.0 m•kg, 7.2
ft•lb)
Right radiator:
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (catch tank):
7 Nm (0.7 m•kg, 5.1
ft•lb)
Bolt (catch tank):
16 Nm (1.6 m•kg, 11
ft•lb)

5-8
CARBURETOR
HANDLING NOTE
Do not loosen the screw (throttle
position sensor) "1" except when
changing the throttle position sen-
sor due to failure because it will
cause a drop in engine perfor-
mance.
REMOVING THE PILOT SCREW
(For EUROPE)
1. Remove:
• Pilot screw "1"
To optimize the fuel flow at a small
throttle opening, each machine's pilot
screw has been individually set at the
factory. Before removing the pilot
screw, turn it in fully and count the
number of turns. Record this number
as the factory-set number of turns
out.
CHECKING THE CARBURETOR
1. Inspect:
• Carburetor body
Contamination→Clean.
• Use a petroleum based solvent for
cleaning. Blow out all passages and
jets with compressed air.
• Never use a wire.
2. Inspect:
•Main jet "1"
• Pilot jet "2"
• Needle jet "3"
• Starter jet "4"
•Pilot air jet "5"
• Leak jet "6"
Damage→Replace.
Contamination→Clean.
• Use a petroleum based solvent for
cleaning. Blow out all passages and
jets with compressed air.
• Never use a wire.
CHECKING THE NEEDLE VALVE
1. Inspect:
• Needle valve "1"
• Valve seat "2"
Grooved wear "a" →Replace.
Dust "b" →Clean.
• Filter "c"
Clogged→Clean.
CHECKING THE THROTTLE
VALVE
1. Check:
• Free movement
Stick→Repair or replace.
Insert the throttle valve "1" into the
carburetor body, and check for free
movement.
CHECKING THE JET NEEDLE
1. Inspect:
• Jet needle "1"
Bends/wear→Replace.
• Clip groove
Free play exists/wear→Replace.
MEASURING AND ADJUSTING
THE FLOAT HEIGHT
1. Measure:
• Float height "a"
Out of specification→Adjust.
Measurement and adjustment
steps:
a. Hold the carburetor in an upside
down position.
• Slowly tilt the carburetor in the op-
posite direction, then take the mea-
surement when the needle valve
aligns with the float arm.
• If the carburetor is level, the weight
of the float will push in the needle
valve, resulting in an incorrect mea-
surement.
b. Measure the distance between
the mating surface of the float
chamber and top of the float using
a vernier calipers.
The float arm should be resting on the
needle valve, but not compressing
the needle valve.
c. If the float height is not within
specification, inspect the valve
seat and needle valve.
d. If either is worn, replace them
both.
Float height:
8.0 mm (0.31 in)

5-15
CAMSHAFTS
CAMSHAFTS
REMOVING THE CYLINDER HEAD COVER
Order Part name Q'ty Remarks
Seat and fuel tank Refer to "REMOVING THE SEAT, FUEL
TANK AND SIDE COVERS" section in the
CHAPTER 3.
Air cut-off valve assembly Refer to "AIR INDUCTION SYSTEM" section.
Engine upper bracket (right) Refer to "ENGINE REMOVAL" section.
Engine upper bracket (left)
1 Spark plug 1
2 Cylinder head breather hose 1
3 Bolt (cylinder head cover) 2
4 Cylinder head cover 1
5 Cylinder head cover gasket 1

5-19
CAMSHAFTS
INSTALLING THE CAMSHAFT
1. Install:
• Exhaust camshaft "1"
• Intake camshaft "2"
Installation steps:
a. Turn the crankshaft counterclock-
wise with a wrench.
• Apply the molybdenum disulfide oil
on the camshafts.
• Apply the engine oil on the decom-
pression system.
b. Align the T.D.C. mark "a" on the
rotor with the align mark "b" on the
crankcase cover when piston is at
T.D.C. on compression stroke.
c. Fit the timing chain "3" onto both
camshaft sprockets and install the
camshafts on the cylinder head.
The camshafts should be installed
onto the cylinder head so that the
punch mark "c" on the exhaust cam-
shaft and the punch mark "d" on the
intake camshaft must align with the
cylinder head surface, as shown in
the illustration.
Do not turn the crankshaft during
the camshaft installation. Damage
or improper valve timing will re-
sult.
d. Install the clips, camshaft caps "4"
and bolts (camshaft cap) "5".
• Before installing the clips, cover the
cylinder head with a clean rag to
prevent the clips from into the cylin-
der head cavity.
• Apply the molybdenum disulfide oil
on the thread of the bolts (camshaft
cap).
• Tighten the bolts to the specified
torque in two or three steps in the
proper tightening sequence as
shown.
The bolts (camshaft cap) must be
tightened evenly, or damage to the
cylinder head, camshaft caps, and
camshaft will result.
2. Install:
• Timing chain tensioner
Installation steps:
a. While pressing the tensioner rod
lightly with fingers, use a thin
screwdriver and wind the tension-
er rod up fully clockwise.
b. With the rod fully wound and the
chain tensioner UP mark "a" fac-
ing upward, install the gasket "1",
the timing chain tensioner "2", and
the gasket "3", and tighten the bolt
"4" to the specified torque.c. Release the screwdriver, check
the tensioner rod to come out and
tighten the gasket "5" and the cap
bolt "6" to the specified torque.
3. Turn:
• Crankshaft
Counterclockwise several turns.
4. Check:
• Rotor T.D.C. mark
Align with the crankcase align
mark.
• Camshaft match marks
Align with the cylinder head sur-
face.
Out of alignment→Adjust.
Bolt (camshaft cap):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (timing chain ten-
sioner):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Tensioner cap bolt:
7 Nm (0.7 m•kg, 5.1
ft•lb)

5-26
VALVES AND VALVE SPRINGS
CHECKING THE VALVE SPRINGS
1. Measure:
• Valve spring free length "a"
Out of specification→Replace.
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 lifter
Scratches/damage→Replace
both lifters and cylinder head.
INSTALLING THE VALVES
1. Apply:
• Molybdenum disulfide oil
Onto the valve stem and valve
stem seal.
2. Install:
• Valves "1"
• Valve spring seats "2"
• Valve stem seals "3"
• Valve springs "4"
• Valve spring retainers "5"
• Make sure that each valve is in-
stalled in its original place, also re-
ferring to the painted color as
follows.
Intake (middle) "a": blue
Intake (right/left) "b": gray
Exhaust "c": brown
• Install the valve springs with the
larger pitch "d" facing upward.
e. Smaller pitch3. Install:
• Valve cotters
While compressing the valve spring
with a valve spring compressor "1" in-
stall the valve cotters.
4. To secure the valve 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.
Free length (valve
spring):
Intake:
39.46 mm (1.55 in)
: 38.46 mm
(1.51 in)
Exhaust:
37.61 mm (1.48 in)
: 36.61 mm
(1.44 in)
Compressed spring
force:
Intake:
130.2–149.8 N at 27.87
mm (13.28–15.28 kg at
27.87 mm, 29.27–
33.68 lb at 1.10 in)
Exhaust:
123.1–141.7 N at 28.38
mm (12.55–14.45 kg at
28.38 mm, 27.67–
31.85 lb at 1.12 in)
Spring tilt limit:
Intake:
2.5°/1.7 mm (0.067 in)
Exhaust:
2.5°/1.6 mm (0.063 in)
Valve spring compres-
sor:
YM-4019/90890-04019