engine YAMAHA YZ450F 2005 Service Manual

3 - 6
INSP
ADJ
COOLANT REPLACEMENT
EC353011
COOLANT REPLACEMENT
WARNING
Do not remove the radiator cap when the
engine is hot.
CAUTION:
Take care so that coolant does not splash
on painted surfaces. If it splashes, wash it
away with water.
1. Place a container under the engine.
2. Remove:
Engine guard 1
Coolant drain bolt 2
3. Remove:
Radiator cap
Drain the coolant completely.
4. Clean:
Cooling system
Thoroughly flush the cooling system with
clean tap water.
5. Install:
Copper washer
Coolant drain bolt
Engine guard
Bolt (engine guard)
6. Fill:
Radiator
Engine
To specified level.
Recommended coolant:
High quality ethylene glycol
anti-freeze containing anti-
corrosion for aluminum engine
Coolant
1 and water (soft water)
2 mixing ratio:
50 %/50 %
Coolant capacity:
1.2 L (1.06 Imp qt, 1.27 US qt)
New
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
T R..34 Nm (3.4 m · kg, 24 ft · lb)

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INSP
ADJ
RADIATOR CAP INSPECTION
CAUTION:
Do not mix more than one type of ethyl-
ene glycol antifreeze containing corro-
sion inhibitors for aluminum engine.
Do not use water containing impurities or
oil.
7. Install:
Radiator cap
Start the engine and warm it up for a sev-
eral minutes.
8. Check:
Coolant level
Coolant level low → Add coolant. Handling notes of coolant:
The coolant is harmful so it should be han-
dled with special care.
WARNING
When coolant splashes to your eye.
Thoroughly wash your eye with water
and see your doctor.
When coolant splashes to your clothes.
Quickly wash it away with water and
then with soap.
When coolant is swallowed.
Quickly make him vomit and take him
to a doctor.
EC355000
RADIATOR CAP INSPECTION
1. Inspect:
Seal (radiator cap) 1
Valve and valve seat 2
Crack/damage → Replace.
Exist fur deposits 3 → Clean or replace.

3 - 10
INSP
ADJTHROTTLE CABLE ADJUSTMENT/
THROTTLE LUBRICATION
EC35A001
THROTTLE CABLE ADJUSTMENT
1. Check:
Throttle grip free play a
Out of specification → Adjust.
Throttle grip free play
a:
3 ~ 5 mm (0.12 ~ 0.20 in)
2. Adjust:
Throttle grip free play
Throttle grip free play adjustment steps:
Slide the adjuster cover.
Loosen the locknut 1.
Turn the adjuster 2 until the specified free
play is obtained.
Tighten the locknut.
NOTE:
Before adjusting the throttle cable free play,
the engine idle speed should be adjusted.
WARNING
After adjusting, turn the handlebar to
right and left and make sure that the
engine idling does not run faster.
21
THROTTLE LUBRICATION
1. Remove:
Cover (throttle cable cap) 1
Cover (grip cap) 2
Throttle cable cap 3
2. Apply:
Lithium soap base grease
On the throttle cable end a.
3. Install:
Throttle cable cap
Screw (throttle cable cap)
Cover (grip cap)
Cover (throttle cable cap)
T R..4 Nm (0.4 m · kg, 2.9 ft · lb)

3 - 11
INSP
ADJHOT STARTER LEVER ADJUSTMENT/
AIR FILTER CLEANING
HOT STARTER LEVER ADJUSTMENT
1. Check:
Hot starter lever free play a
Out of specification → Adjust.
2. Adjust:
Hot starter lever free play
NOTE:
After adjustment, check proper operation of
hot starter.
Hot starter lever free play
a:
3 ~ 6 mm (0.12 ~ 0.24 in)
Hot starter lever free play adjustment
steps:
Loosen the locknut 1.
Turn the adjuster 2 until free play a is
within the specified limits.
Tighten the locknut.
EC35G040
AIR FILTER CLEANING
NOTE:
Proper air filter maintenance is the biggest key
to preventing premature engine wear and
damage.
CAUTION:
Never run the engine without the air filter
element in place; this would allow dirt and
dust to enter the engine and cause rapid
wear and possible engine damage.
1. Remove:
Seat
Fitting bolt 1
Washer 2
Air filter element 3
Filter guide 4

3 - 13
INSP
ADJ
7. Install:
Air filter element 1
Washer
Fitting bolt
NOTE:
Align the projection a on filter guide with the
hole b in air filter case.
T R..2 Nm (0.2 m · kg, 1.4 ft · lb)
ENGINE OIL LEVEL INSPECTION
1. Stand the machine on a level surface.
NOTE:
When checking the oil level make sure that
the machine is upright.
Place the machine on a suitable stand.
WARNING
Never remove the oil tank cap just after
high speed operation. The heated oil could
spurt out. causing danger. Wait until the oil
cools down to approximately 70 °C (158 °F).
2. Idle the engine more than 3 minutes while
keeping the machine upright. Then stop the
engine and inspect the oil level.
3. Remove:
Oil tank cap 1
1
ENGINE OIL LEVEL INSPECTION

3 - 14
INSP
ADJ
ENGINE OIL LEVEL INSPECTION
4. Inspect:
Oil level
Oil level should be between maximum a
and minimum b marks.
Oil level low → Add oil to proper level.
NOTE:
When inspecting the oil level, do not screw the
oil level gauge into the oil tank.
Insert the gauge lightly.
(For USA and CDN)
CAUTION:
Do not add any chemical additives.
Engine oil also lubricates the clutch and
additives could cause clutch slippage.
Do not allow foreign material to enter the
crankcase.
(Except for USA and CDN)
CAUTION:
Do not add any chemical additives or use
oils with a grade of CD
a or higher.
Do not use oils labeled “ENERGY CON-
SERVING II”
b or higher. Engine oil also
lubricates the clutch and additives could
cause clutch slippage.
Do not allow foreign materials to enter the
crankcase.
Recommended oil:
At 5 °C (40 °F) or higher
È
Yamalube 4 (20W-40) or SAE
20W-40 type SG motor oil
(Non-Friction modified)
At 15 °C (60 °F) or lower
É
Yamalube 4 (10W-30) or SAE
10W-30 type SG motor oil
(Non-Friction modified)
and/or
Yamalube 4-R (15W-50)
(Non-Friction modified)
Recommended oil:
Refer to the following chart for
selection of oils which are
suited to the atmospheric
temperatures.
Recommended engine oil classi-
fication:
API STANDARD:
API “SG” or higher grade
(Designed primarily for
motorcycles)
a
b
-20
-4-10
140
3010
5020
6830
8640 50
104
122 ˚CTemp.
˚F
10W-30
10W-40
20W-40
20W-50
15W-40
a
b

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INSP
ADJ
ENGINE OIL REPLACEMENT
5. Start the engine and let it warm up for sev-
eral minutes.
CAUTION:
When the oil tank is empty, never start the
engine.
6. Idle the engine more than 10 seconds
while keeping the machine upright. Then
stop the engine and add the oil to the maxi-
mum level.
7. Install:
Oil tank cap
ENGINE OIL REPLACEMENT
1. Start the engine and let it warm up for sev-
eral minutes.
2. Stop the engine and place an oil pan under
the drain bolt.
3. Remove:
Oil tank plug 1
Oil filler cap 2
Drain bolt (with gasket) 3
Oil filter drain bolt (O-ring) 4
Drain bolt (with gasket) 5
Drain bolt (with gasket) 6
Drain the crankcase and oil tank (frame)
of its oil.
4. Remove:
Engine skid plate
Engine oil hose clamp 1
Bolt (engine oil hose) 2
Engine oil hose 3
Oil strainer (frame) 4
5. Clean:
Oil strainer (frame)

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INSP
ADJ
ENGINE OIL REPLACEMENT
6. If the oil filter is to be replaced during this
oil change, remove the following parts and
reinstall them.
7. Install:
Plain washer 1
Oil strainer (frame) 2
Engine oil hose 3
Bolt (engine oil hose) 4
Engine oil hose clamp 5
Engine skid plate
8. Install:
Gaskets
Oil filter drain bolt
Drain bolt (crankcase rear)
Drain bolt (crankcase left)
Drain bolt (frame)
9. Fill:
Crankcase Replacement steps:
Remove the oil filter cover 1 and oil filter
element 2.
Check the O-rings 3, if cracked or dam-
aged, replace them with a new one.
Install the oil filter element and oil filter
cover.
T R..
Oil filter cover:
10 Nm (1.0 m  kg, 7.2 ft  lb)
Oil quantity:
Periodic oil change:
1.0 L (0.88 Imp qt, 1.06 US qt)
With oil filter replacement:
1.1 L (0.97 Imp qt, 1.16 US qt)
Total amount:
1.2 L (1.06 Imp qt, 1.27 US qt)
New
T R..70 Nm (7.0 m · kg, 50 ft · lb)
T R..8 Nm (0.8 m · kg, 5.8 ft · lb)
T R..2 Nm (0.2 m · kg, 1.4 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
New
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
T R..20 Nm (2.0 m · kg, 14 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
T R..23 Nm (2.3 m · kg, 17 ft · lb)

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INSP
ADJ
PILOT SCREW ADJUSTMENT
10. Install:
Oil filler plug
11. Inspect:
Engine (for oil leaks)
Oil level
Refer to “ENGINE OIL LEVEL INSPEC-
TION”.
12. Check:
Oil pressure
Checking steps:
Slightly loosen the oil gallery bolt 1.
Start the engine and keep it idling until oil
starts to seep from the oil gallery bolt. If no
oil comes out after one minute, turn the
engine off so it will not seize.
Check oil passages, oil filter and oil pump
for damage or leakage.
Start the engine after solving the prob-
lem(s) and recheck the oil pressure.
Tighten the oil gallery bolt to specification.
T R..
Oil gallery bolt:
10 Nm (1.0 m  kg, 7.2 ft  lb)
PILOT SCREW ADJUSTMENT
1. Adjust:
Pilot screw 1
Adjusting steps:
NOTE:
To optimize the fuel flow at a smaller throttle
opening, each machine’s pilot screw has
been individually set at the factory. Before
adjusting the pilot screw, turn it in fully and
count the number of turns. Record this num-
ber as the factory-set number of turns out.
Turn in the pilot screw until it is lightly
seated.
Turn out the pilot screw by the factory-set
number of turns.
Pilot screw:
1-3/4 turns out (example)

3 - 18
INSP
ADJIDLE SPEED ADJUSTMENT/
VALVE CLEARANCE ADJUSTMENT
EC35M021
IDLE SPEED ADJUSTMENT
1. Start the engine and thoroughly warm it up.
2. Adjust:
Idle speed
VALVE CLEARANCE ADJUSTMENT
NOTE:
The valve clearance should be adjusted
when the engine is cool to the touch.
The piston must be at Top Dead Center
(T.D.C.) on compression stroke to check or
adjust the valve clearance.
1. Remove:
Seat
Fuel tank
Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section in the CHAPTER 4.
2. Remove:
Carburetor
Refer to “CARBURETOR” section in the
CHAPTER 4.
Spark plug
Engine stay (upper)
Cylinder head cover
Refer to “CAMSHAFTS” section in the
CHAPTER 4. Adjustment steps:
Adjust the pilot screw.
Refer to “PILOT SCREW ADJUSTMENT”
section.
Turn the throttle stop screw 1 until the
specified engine idling speed.
NOTE:
Using a digital engine tachometer for idle
speed adjustment, detect the engine idling
speed by bringing the sensing element c of
the engine tachometer close to the ignition
coil 2.
To increase idle speed
→
Turn the throttle stop screw
1 in
a.
To decrease idle speed
→
Turn the throttle stop screw
1 out
b.
Engine idling speed:
1,900 ~ 2,100 r/min
c2