2005 YAMAHA WR 450F engine

3 - 22
INSP
ADJ
6. Install:
All removed parts
NOTE:
Install all removed parts in reversed order of
their removal.Locate the rounded-off value and the mea-
sured valve clearance in the chart “PAD
SELECTION TABLE”. The field where
these two coordinates intersect shows the
new pad number to use.
NOTE:
Use the new pad number only as a guide
when verifying the valve clearance adjust-
ment.
Install the new pads 6 and the valve lift-
ers 7.
NOTE:
Apply the engine oil on the valve lifters.
Apply the molybdenum disulfide oil on the
valve stem ends.
Valve lifter must turn smoothly when
rotated with a finger.
Be careful to reinstall valve lifters and
pads in their original place.
Install the camshafts (exhaust and intake),
the timing chain and the camshaft caps.
Refer to “CAMSHAFTS” section in the
CHAPTER 4.
T R..
Bolt (camshaft cap):
10 Nm (1.0 m  kg, 7.2 ft  lb)
Install the timing chain tensioner.
Refer to “CAMSHAFTS” section in the
CHAPTER 4.
NOTE:
Turn the crankshaft counterclockwise sev-
eral turns so that the installed parts settle
into the right position.
Recheck the valve clearance.
If the clearance is still incorrect, repeat all
the clearance adjustment steps until the
specified clearance is obtained.
VALVE CLEARANCE ADJUSTMENT

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INSP
ADJ
SPARK ARRESTER CLEANING (For USA)
WARNING
Be sure the exhaust pipe and silencer are
cool before cleaning the spark arrester.
Do not start the engine when cleaning the
exhaust system.
1. Remove:
Screw (silencer cap) 1
1
2. Remove:
Bolt (spark arrester) 1
1
3. Remove:
Tail pipe 1
Gasket (tail pipe) 2
Spark arrester 3
Pull the spark arrester out of the silencer.
Gasket (spark arrester) 4
4. Clean:
Spark arrester
Tap the spark arrester lightly, then use a
wire brush to remove any carbon depos-
its.
5. Install:
Gasket (spark arrester)
Spark arrester
Insert the spark arrester into the silencer
and align the bolt holes.
Gasket (tail pipe)
Bolt (spark arrester)
12
34
T R..7 Nm (0.7 m · kg, 5.1 ft · lb)
6. Install:
Silencer cap
NOTE:
First tighten the two screws a located horizon-
tally apart, and then tighten the others.aa
T R..5 Nm (0.5 m · kg, 3.6 ft · lb)
SPARK ARRESTER CLEANING (For USA)

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INSP
ADJ
DRIVE CHAIN SLACK ADJUSTMENT
DRIVE CHAIN SLACK ADJUSTMENT
1. Elevate the rear wheel by placing the suit-
able stand under the engine.
2. Check:
Drive chain slack a
Above the seal guard installation bolt.
Out of specification → Adjust.
NOTE:
Before checking and/or adjusting, rotate the
rear wheel through several revolutions and
check the slack several times to find the tight-
est point. Check and/or adjust the chain slack
with the rear wheel in this “tight chain” position.
Drive chain slack:
48 ~ 58 mm (1.9 ~ 2.3 in)
3. Adjust:
Drive chain slack
Drive chain slack adjustment steps:
Loosen the axle nut 1 and locknuts 2.
Adjust the chain slack by turning the
adjusters 3.
To tighten
→Turn the adjuster
3 coun-
terclockwise.
To loosen
→Turn the adjuster
3 clock-
wise and push wheel for-
ward.
Turn each adjuster exactly the same
amount to maintain correct axle alignment.
(There are marks a on each side of the
chain puller alignment.)
NOTE:
Turn the adjuster so that the chain is in line
with the sprocket, as viewed from the rear.
CAUTION:
Too small chain slack will overload the
engine and other vital parts; keep the
slack within the specified limits.

3 - 36
INSP
ADJFRONT FORK INTERNAL PRESSURE RELIEVING/
FRONT FORK REBOUND DAMPING FORCE ADJUSTMENT
FRONT FORK INTERNAL PRESSURE
RELIEVING
NOTE:
If the front fork initial movement feels stiff dur-
ing a run, relieve the front fork internal pres-
sure.
1. Elevate the front wheel by placing a suit-
able stand under the engine.
2. Remove the air bleed screw 1 and release
the internal pressure from the front fork.
3. Install:
Air bleed screw
T R..1 Nm (0.1 m · kg, 0.7 ft · lb)
EC36H002
FRONT FORK REBOUND DAMPING FORCE
ADJUSTMENT
1. Adjust:
Rebound damping force
By turning the adjuster 1.
Stiffer a →Increase the rebound damp-
ing force. (Turn the adjuster
1 in.)
Softer b →Decrease the rebound damp-
ing force. (Turn the adjuster
1 out.)
Extent of adjustment:
Maximum Minimum
Fully turned in
position20 clicks out (from
maximum position)

3 - 39
INSP
ADJREAR SHOCK ABSORBER SPRING PRELOAD
ADJUSTMENT
REAR SHOCK ABSORBER SPRING
PRELOAD ADJUSTMENT
1. Elevate the rear wheel by placing the suit-
able stand under the engine.
2. Remove:
Rear frame
3. Loosen:
Locknut 1
4. Adjust:
Spring preload
By turning the adjuster 2.
* For EUROPE
** For AUS, NZ and ZA
NOTE:
Be sure to remove all dirt and mud from
around the locknut and adjuster before
adjustment.
The length of the spring (installed) changes
1.5 mm (0.06 in) per turn of the adjuster.
CAUTION:
Never attempt to turn the adjuster beyond
the maximum or minimum setting.
5. Tighten:
Locknut
6. Install:
Rear frame (upper)
Rear frame (lower) Stiffer
→Increase the spring preload.
(Turn the adjuster
2 in.)
Softer
→Decrease the spring preload.
(Turn the adjuster
2 out.)
Spring length (installed)
a:
Standard length Extent of adjustment
248 mm (9.76 in)
* 253 mm (9.96 in)
** 247 mm (9.72 in)237.5 ~ 258.5 mm
(9.35 ~ 10.18 in)
T R..32 Nm (3.2 m · kg, 23 ft · lb)
T R..29 Nm (2.9 m · kg, 21 ft · lb)

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INSP
ADJ
STEERING HEAD INSPECTION AND ADJUSTMENT
2. Inspect:
Bearing free play
Exist play → Replace.
STEERING HEAD INSPECTION AND
ADJUSTMENT
1. Elevate the front wheel by placing a suit-
able stand under the engine.
2. Check:
Steering shaft
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 steering ring
nut.
4. Adjust:
Steering ring nut
Steering ring nut adjustment steps:
Remove the headlight.
Remove the handlebar and handle crown.
Loosen the ring nut 1 using the ring nut
wrench 2.
Ring nut wrench:
YU-33975/90890-01403

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INSP
ADJ
ELECTRICAL/SPARK PLUG INSPECTION
EC370000
ELECTRICAL
EC371001
SPARK PLUG INSPECTION
1. Remove:
Spark plug
2. Inspect:
Electrode 1
Wear/damage → Replace.
Insulator color 2
Normal condition is a medium to light tan
color.
Distinctly different color → Check the
engine condition.
NOTE:
When the engine runs for many hours at low
speeds, the spark plug insulator will become
sooty, even if the engine and carburetor are in
good operating condition.
3. Measure:
Plug gap a
Use a wire gauge or thickness gauge.
Out of specification → Regap.
Spark plug gap:
0.7 ~ 0.8 mm (0.028 ~ 0.031 in)
4. Clean the plug with a spark plug cleaner if
necessary.
5. Tighten:
Spark plug
NOTE:
Before installing a spark plug, clean the gas-
ket surface and plug surface.
Finger-tighten a the spark plug before torqu-
ing to specification b.
T R..13 Nm (1.3 m · kg, 9.4 ft · lb)

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INSP
ADJ
IGNITION TIMING CHECK
IGNITION TIMING CHECK
1. Remove:
Timing plug 1
1
2. Attach:
Timing light
Inductive tachometer
To the ignition coil lead (orange lead 1).
Timing light:
YM-33277-A/90890-03141
1
3. Adjust:
Engine idling speed
Refer to “IDLE SPEED ADJUSTMENT”.
4. Check:
Ignition timing
Visually check the stationary pointer a is
within the firing range b on the rotor.
Incorrect firing range → Check rotor and
pickup assembly.
5. Install:
Timing plug