engine YAMAHA YZ450F 2003 Manual PDF

4 - 47
ENGCYLINDER AND PISTON
2. Position:
Top ring
2nd ring
Oil ring
Offset the piston ring end gaps as
shown.
aTop ring end
b2nd ring end
cOil ring end (upper)
dOil ring
eOil ring end (lower)
3. Install:
Piston 1
Piston pin 2
Piston pin clips 3
NOTE:
Apply engine oil onto the piston pin and pis-
ton.
Be sure that the arrow mark a on the piston
points to the exhaust side of the engine.
Before installing the piston pin clip, cover the
crankcase with a clean rag to prevent the
piston pin clip from falling into the crankcase.
Install the piston pin clips with their ends fac-
ing downward.
4. Lubricate:
Piston
Piston rings
Cylinder
NOTE:
Apply a liberal coating of engine oil.
Cylinder
1. Install:
Dowel pins
O-ring
Gasket 1
Cylinder 2
NOTE:
Install the cylinder with one hand while com-
pressing the piston rings with the other hand.
CAUTION:
Pass the timing chain 3 through the tim-
ing chain cavity.
Be careful not to damage the timing chain
guide 4 during installation.
2. Install:
Bolt (cylinder)
45°
135°135°
a
b ced
3New
New
New
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)

4 - 48
ENGCLUTCH
CLUTCH
CLUTCH
Extent of removal:1 Push rod and push lever removal2 Push pod 1 disassembly
3 Friction plate and clutch plate removal4 Clutch housing removal
Extent of removal Order Part name Q’ty Remarks
CLUTCH REMOVAL
Preparation for removal Drain the engine oil. Refer to “ENGINE OIL REPLACEMENT”
section in the CHAPTER 3.
Brake pedal Refer to “ENGINE REMOVAL” section.
Clutch cable Disconnect at engine side.
1 Clutch cover 1
2 Gasket 1
3 Dowel pin 2
4 Clutch spring 6
5 Pressure plate 1
6 Push rod 1 1
7 Circlip 1
8 Plain washer 1
9 Bearing 1
10 Ball 1
11Push rod 2
1
41
2
3
1

4 - 52
ENGCLUTCH
EC4A5000
ASSEMBLY AND INSTALLATION
Push lever
1. Install:
Push lever 1
Bolt (push lever)
NOTE:
Apply the lithium soap base grease on the oil
seal lip.
Apply the engine oil on the push lever.
Fit the seat plate 2 in the groove a of the
push lever and tighten the bolt (seat plate).
2
1a
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
Clutch
1. Install:
Primary driven gear 1
Thrust washer 2
Clutch boss 3
NOTE:
Apply the engine oil on the primary driven gear
inner circumference.
2. Install:
Lock washer 1
Nut (clutch boss) 2
NOTE:
Use the clutch holding tool 3 to hold the clutch
boss.
ÅFor USA and CDN
ıExcept for USA and CDN
Clutch holding tool:
YM-91042/90890-04086
New
T R..75 Nm (7.5 m · kg, 54 ft · lb)
Åı

4 - 53
ENGCLUTCH
3. Bend the lock washer 1 tab.
4. Install:
Friction plate 1
Clutch plate 2
NOTE:
Install the clutch plates and friction plates
alternately on the clutch boss, starting with a
friction plate and ending with a friction plate.
Apply the engine oil on the friction plates and
clutch plates.
2 1
E
5. Install:
Bearing 1
Plain washer 2
Circlip 3
To push rod 1 4.
NOTE:
Apply the engine oil on the bearing and plain
washer.
New
6. Install:
Push rod 2 1
Ball 2
Push rod 1 3
NOTE:
Apply the engine oil on the push rod 1, 2 and
ball.

4 - 55
ENG
OIL FILTER, WATER PUMP AND CRANKCASE COVER
(RIGHT)
OIL FILTER, WATER PUMP AND CRANKCASE COVER (RIGHT)
OIL FILTER, WATER PUMP AND CRANKCASE COVER (RIGHT)
Extent of removal:1 Oil filter removal2 Water pump removal
3 Crankcase cover (right) removal
Extent of removal Order Part name Q’ty Remarks
OIL FILTER, WATER PUMP
AND CRANKCASE COVER
(RIGHT) REMOVAL
Preparation for removal Drain the engine oil. Refer to “ENGINE OIL REPLACEMENT”
section in the CHAPTER 3.
Drain the coolant. Refer to “COOLANT REPLACEMENT”
section in the CHAPTER 3.
Exhaust pipe Refer to “EXHAUST PIPE AND
SILENCER” section.
Brake pedal Refer to “ENGINE REMOVAL” section.
Clutch cover Refer to “CLUTCH” section.
1 Oil filter cover 1
2 Oil filter 1
3 Coolant pipe 2 1
4 Water pump housing 1
5 Pin 2
6 Oil delivery pipe 1
1
2
3

4 - 59
ENG
OIL FILTER, WATER PUMP AND CRANKCASE COVER
(RIGHT)
EC4G5220
Impeller shaft
1. Install:
Impeller shaft 1
Plain washer 2
Impeller 3
NOTE:
Take care so that the oil seal lip is not dam-
aged or the spring does not slip off its posi-
tion.
When installing the impeller shaft, apply the
engine oil on the oil seal lip, bearing and
impeller shaft. And install the shaft while
turning it.
Hold the impeller shaft on its width across
the flats a with spanners, etc. and install the
impeller.
T R..14 Nm (1.4 m · kg, 10 ft · lb)
Crankcase cover (right)
1. Install:
Dowel pin 1
O-ring 2
Collar 3
Gasket 4 New
2. Install:
Crankcase cover (right) 1
Bolt
NOTE:
Apply the engine oil on the impeller shaft
end.
When installing the crankcase cover onto the
crankcase, be sure that the impeller shaft
end 2 aligns with the balancer end slot 3.
Tighten the bolts in stage, using a crisscross
pattern.
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)

4 - 64
ENGBALANCER
ASSEMBLY AND INSTALLATION
Balancer, balancer drive gear and balancer
driven gear
1. Install:
Balancer 1
NOTE:
When installing the balancer shaft, align the
center of the balancer shaft weight a along
the line connecting the centers of the crank-
shaft and balancer shaft.
2. Install:
Balancer driven gear 1
NOTE:
Install the balancer driven gear onto the bal-
ancer while aligning the punch mark a on the
balancer driven gear with the lower spline b
on the balancer end.
3. Install:
Balancer drive gear 1
NOTE:
Align the punched mark a on the balancer
drive gear with the punched mark b on the
balancer driven gear.
Align the punched mark c on the balancer
drive gear with the lower spline d on the
crankshaft.
4. Install:
Lock washer 1
Nut (balancer) 2
Primary drive gear 3
Nut (primary drive gear) 4
NOTE:
Install the primary drive gear with its stepped
side b facing the engine.
Place an aluminum plate a between the
teeth of the balancer drive gear 5 and
driven gear 6.
5. Bend the lock washer tab.
T R..50 Nm (5.0 m · kg, 36 ft · lb)
T R..75 Nm (7.5 m · kg, 54 ft · lb)
b3

4 - 67
ENGOIL PUMP
INSPECTION
Oil pump
1. Inspect:
Oil pump drive gear
Oil pump driven gear
Rotor housing
Oil pump cover
Cracks/wear/damage → Replace.
2. Measure:
Tip clearance a
Between the inner rotor 1 and the
outer rotor 2.
Tip clearance b
Between the outer rotor 2 and the rotor
housing 3.
Out of specification → Replace the oil
pump.
Tip clearance a:
0.12 mm or less
(0.0047 in or less)
<Limit>: 0.20 mm (0.008 in)
Tip clearance b:
0.09 ~ 0.17 mm (0.0035 ~ 0.0067 in)
<Limit>: 0.24 mm (0.009 in)
Side clearance c:
0.03 ~ 0.10 mm (0.0012 ~ 0.0039 in)
<Limit>: 0.17 mm (0.007 in)
3. Check:
Unsmooth → Repeat steps #1 and #2
or replace the defective parts.
ASSEMBLY AND INSTALLATION
Oil pump
1. Install:
Oil pump drive shaft 1
Washer 2
Pin 3
Inner rotor 1 4
NOTE:
Apply the engine oil on the oil pump drive
shaft and inner rotor 1.
Fit the pin into the groove in the inner rotor 1.

4 - 68
ENGOIL PUMP
2. Install:
Outer rotor 1 1
NOTE:
Apply the engine oil on the outer rotor 1.
3. Install:
Oil pump cover 1
Screw (oil pump cover) 2
Pin 3
Inner rotor 2 4
Circlip 5
NOTE:
Apply the engine oil on the oil pump drive
shaft end and inner rotor 2.
Fit the pin into the groove in the inner rotor 2.
4. Install:
Outer rotor 2 1
Dowel pin 2
Oil pump assembly 3
Bolt (oil pump assembly)
[L = 30 mm (1.18 in)] 4
Bolt (oil pump assembly)
[L = 25 mm (0.98 in)] 5
NOTE:
Apply the engine oil on the outer rotor 2.
T R..2 Nm (0.2 m · kg, 1.4 ft · lb)
New
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
5. Install:
Oil pump drive gear 1
Plate washer 2
Circlip 3
NOTE:
Apply the engine oil on the oil pump drive gear
inner circumference.
New

4 - 73
ENGKICK AXLE AND SHIFT SHAFT
EC4B5111
Stopper lever
1. Install:
Torsion spring 1
Stopper lever 2
Bolt (stopper lever) 3
NOTE:
Align the stopper lever roller with the slot on
segment.
Shift guide and shift lever assembly
1. Install:
Spring 1
Pawl pin 2
Pawl 3
To shift lever 4.
NOTE:
Apply the engine oil on the springs, pawl pins
and pawls.
2. Install:
Shift lever assembly 1
To shift guide 2.
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
2
1
3. Install:
Shift lever assembly 1
Shift guide 2
NOTE:
The shift lever assembly is installed at the
same time as the shift guide.
Apply the engine oil on the bolt (segment)
shaft.
4. Install:
Bolt (shift guide) 1
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)