2011 YAMAHA YZ450F run flat

3-8
ENGINE
ADJUSTING THE THROTTLE
CABLE FREE PLAY
1. Check:• Throttle grip free play "a"
Out of specification →Adjust.
2. Adjust: • Throttle grip free play
Throttle grip free play adjustment
steps:
a. Slide the adjuster cover.
b. Loosen the locknut "1".
c. Turn the adjuster "2" until the specified free play is obtained.
d. Tighten the locknut.
Before adjusting the throttle cable
free play, the engine idle speed
should be adjusted.
After adjusting th e throttle cable
free play, start the engine and turn
the handlebar to right and left and
make sure that the engine idling
does not run faster.
LUBRICATING THE THROTTLE
1. Remove: • Cover (throttle cable cap) "1"
• Cover (grip cap) "2"
• Throttle grip cap "3" 2. Apply:
• Lithium soap base greaseOn the throttle cable end "a".
3. Install: • Throttle grip cap
• Screw (throttle grip cap)
• Cover (grip cap)
• Cover (throttle cable cap)
CHECKING THE THROTTLE
VALVE PULLY COVER DRAIN
HOSE
Drain the water that stays in the throt-
tle valve pulley cove r after a machine
wash or a rainy weather ride.
1. Drain the water by picking up the flat portion of the lower end "a" of
the drain hose.
CLEANING THE AIR FILTER
ELEMENT
1. Remove: •Seat
2. Remove the fuel tank bolt (front) "1" and lift the fuel tank.
Hold the fuel tank in position by the
use of the fuel tank holding cable "2".
3. Remove:• Mounting bolt for air filter case
cover 4. Loosen and release the binder "1"
and lift the air filter case lid.
Hold the air filter case lid by the use of
the binder.
5. Remove:• Air filter guide
• Air filter element "1"
Do not remove the thin sheet (air
filter element 2) "2" under the air
filter element unless it is dirty. It is
there to prevent foreign matter
from dropping in to the throttle
body. If the thin sheet must be re-
moved for cleaning, lift it carefully
to avoid loosening the dirt, and
then temporarily block the throttle
body opening with a clean, lint-free
cloth.
6. Clean: • Air filter element
Clean them with solvent.
After cleaning, remo ve the remaining
solvent by squeezing the element.
• Do not twist the element when squeezing the element.
• Leaving too much of solvent in
the element may result in poor
starting.
7. Inspect:• Air filter elementDamage → Replace.
Throttle grip free play
"a":
3–5 mm (0.12–0.20 in)
Screw (throttle grip cap): 4 Nm (0.4 m•kg, 2.9
ft•lb)

3-21
CHASSIS
CHECKING THE TIRE PRESSURE
1. Measure:
• Tire pressure
Out of specification→Adjust.
• Check the tire while it is cold.
• Loose bead stoppers allow the tire
to slip off its position on the rim
when the tire pressure is low.
• A tilted tire valve stem indicates that
the tire slips off its position on the
rim.
• If the tire valve stem is found tilted,
the tire is considered to be slipping
off its position. Correct the tire posi-
tion.
CHECKING AND TIGHTENING THE
SPOKES
The following procedure applies to all
of the spokes.
1. Check:
• Spokes
Bend/damage→Replace.
Loose spoke→Retighten.
Tap the spokes with a screw-
driver.
A tight spoke will emit a clear, ringing
tone; a loose spoke will sound flat.
2. Tighten:
• Spokes
(with a spoke nipple wrench "1")
Be sure to retighten these spokes be-
fore and after break-in.
CHECKING THE WHEELS
1. Inspect:
• Wheel runout
Elevate the wheel and turn it.
Abnormal runout→ Replace.
2. Inspect:
• Bearing free play
Exist play→Replace.
CHECKING AND ADJUSTING THE
STEERING HEAD
1. Place a stand under the engine to
raise the front wheel off the
ground. WARNING! Securely
support the vehicle so that
there is no danger of it falling
over.
2. Check:
• Steering stem
Grasp the bottom of the forks and
gently rock the fork assembly
back and forth.
Free play→Adjust steering head.3. Check:
• Steering smooth action
Turn the handlebar lock to lock.
Unsmooth action→Adjust steer-
ing ring nut.
4. Adjust:
• Steering ring nut
Steering ring nut adjustment
steps:
a. Remove the number plate.
b. Remove the handlebar and upper
bracket.
c. Loosen the steering ring nut "1"
using the steering nut wrench "2".
d. Tighten the steering ring nut "3"
using steering nut wrench "4".
• Apply the lithium soap base grease
on the thread of the steering stem.
• Set the torque wrench to the steer-
ing nut wrench so that they form a
right angle.
Standard tire pressure:
100 kPa (1.0 kgf/cm2,
15 psi)
Spoke nipple wrench:
YM-01521/90980-01521
Spokes:
3 Nm (0.3 m•kg, 2.2
ft•lb)
Steering nut wrench:
YU-33975/90890-01403
Steering nut wrench:
YU-33975/90890-01403
Steering ring nut (initial
tightening):
38 Nm (3.8 m•kg, 27
ft•lb)

4-46
AC MAGNETO
REMOVING THE ROTOR
1. Remove:
• Nut (rotor) "1"
• Washer
2. Remove:
• Rotor "1"
Use the rotor puller 2.
CHECKING THE AC MAGNETO
1. Inspect:
• Rotor inner surface "a"
• Stator outer surface "b"
Damage → Inspect the crank-
shaft runout and crankshaft bear-
ing.
CHECKING THE WOODRUFF KEY
1. Inspect:
• Woodruff key "1"
Damage → Replace.INSTALLING THE AC MAGNETO
1. Install:
• Stator "1"
• Screw (stator) "2"
• Crankshaft position sensor "3"
• Holder "4"
• Bolt (crankshaft position sensor)
"5"
• Apply the sealant on the grommet
of the AC magneto lead.
• Tighten the screws using the T30
bit.
• Pass the crankshaft position sensor
lead "a" this side of the stator lead
"b".
• Install the holder so that the projec-
tion "c" on the holder contacts the
stopper.
2. Install:
• Woodruff key "1"
• Rotor "2"
• Degrease the contact surfaces of
the tapered portions of the crank-
shaft and rotor.
• When installing the woodruff key,
make sure that its flat surface "a" is
in parallel with the crankshaft center
line "b".
• When installing the rotor, align the
keyway "c" of the rotor with the
woodruff key.
3. Install:
• Washer
• Nut (rotor) "1"
4. Connect:
• AC magneto lead
Refer to "CABLE ROUTING DIA-
GRAM" section in the CHAPTER
2.
5. Install:
• Dowel pin
• Gasket (left crankcase cover)
• Left crankcase cover "1"
• Hose guide (cylinder head breath-
er hose) "2"
• Bolt (left crankcase cover)
Tighten the bolts in stage, using a
crisscross pattern.
Rotor puller:
YM-04151/90890-04151
Screw (stator):
8 Nm (0.8 m•kg,
5.8ft•lb)
Bolt (crankshaft position
sensor):
10 Nm (1.0 m•kg, 7.2
ft•lb)
YAMAHA Bond No. 1215
(ThreeBond
® No. 1215):
90890-85505
Nut (rotor):
65 Nm (6.5 m•kg, 47
ft•lb)
Bolt (left crankcase cov-
er):
10 Nm (1.0 m•kg, 7.2
ft•lb)

8-1
CHASSIS
TUNING
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 race, 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 race 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 fr om 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 PARTS
TIRE 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 amount.
2. Setting of spring preload
• Change the spring.
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 AMOUNT AND
CHARACTERISTICS OF FORK OIL
Damping characteristic near the final
stroke can be changed by changing
the fork oil amount.
Adjust the oil amount in 5 cm3 (0.2
Imp oz, 0.2 US oz) increments or
decrements. Too small oil amount
causes the front fork to produce a
noise at full rebound or the rider to
feel some pressure on his hands
or body. Alternatively, too large oil
amount will cause the air spring
characteristics to have a tendency
to be stiffer with the consequent
deteriorated performance and
characteristics. Therefore, 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 ratio 48/13
(3.692)
* 49/13
(3.769)
* Except for USA and CDN
Part name Size Part number
Drive
sprocket "1" (STD) 13T 9383E-13233
Rear wheel
sprocket "2" 47T 17D-25447-50
(STD) 48T 17D-25448-50
* (STD) 49T 17D-25449-50 50T 17D-25450-50
51T 17D-25451-50
52T 17D-25452-50
* Except for USA and CDN
Standard tire pressure:100 kPa (1.0 kgf/cm
2,
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)
Standard oil amount:
355 cm3 (12.5 Imp oz,
12.0 US oz)
Extent of adjustment:
300–365 cm
3 (10.6–12.8
Imp oz, 10.1–12.3 US
oz)