2003 YAMAHA YZ450F oil

4 - 75
ENGKICK AXLE AND SHIFT SHAFT
3. Install:
Spring guide 1
NOTE:
Slide the spring guide into the kick axle, make
sure the groove a in the spring guide fits on
the stopper of the torsion spring.
4. Install:
Kick axle assembly 1
Plain washer 2
NOTE:
Apply the molybdenum disulfide grease on
the contacting surfaces of the kick axle stop-
per a and stopper plate 3.
Apply the engine oil on the kick axle.
Slide the kick axle assembly into the crank-
case and make sure the kick axle stopper fits
into the stopper plate.
5. Hook:
Torsion spring 1
NOTE:
Turn the torsion spring clockwise and hook
into the proper hole a in the crankcase.
Kick idle gear
1. Install:
Kick idle gear 1
Plain washer 2
Circlip 3
NOTE:
Install the kick idle gear with its depressed
side a toward you.
Apply the engine oil on the kick idle gear
inner circumference.
New

4 - 80
ENGENGINE REMOVAL
EC4M0000
ENGINE REMOVAL
Extent of removal Order Part name Q’ty Remarks
ENGINE REMOVAL
Preparation for removal Hold the machine by placing the
suitable stand under the frame.
WARNING
Support the machine securely so there is no
danger of it falling over.
Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Carburetor Refer to “CARBURETOR” section.
Exhaust pipe and silencer Refer to “EXHAUST PIPE AND
SILENCER” section.
Clutch cable and guide Disconnect at engine side.
Radiator Refer to “RADIATOR” section.
Shift pedal Refer to “CDI MAGNETO” section.
Cylinder head breather hose and
oil tank breather hoseRefer to “CAMSHAFTS” section.
Drain the engine oil Refer to “ENGINE OIL REPLACEMENT”
section in the CHAPTER 3.
Ignition coil
Disconnect the CDI magneto lead.

4 - 81
ENGENGINE REMOVAL
Extent of removal:1 Engine removal
Extent of removal Order Part name Q’ty Remarks
1 Engine skid plate (front) 1
2 Neutral switch 1
3 Oil hose 2
4 Chain cover 1
5 Nut (drive sprocket) 1
Refer to “REMOVAL POINTS”. 6 Lock washer 1
7 Drive sprocket 1
8 Clip 1
9 Bolt (brake pedal) 1
10 Brake pedal 1
11 Engine upper bracket (right) 1
12 Engine upper bracket (left) 1
13 Engine lower bracket 2
14 Engine mounting bolt 3
15 Pivot shaft 1
Refer to “REMOVAL POINTS”.
16 Engine 1
1

4 - 84
ENGENGINE REMOVAL
2. Install:
Lock washer 1
Nut (drive sprocket) 2
NOTE:
Tighten the nut while applying the rear brake.
New
T R..75 Nm (7.5 m · kg, 54 ft · lb)
3. Bend the lock washer tab to lock the nut.
4. Install:
Chain guide
Chain cover 1
Screw (chain cover) 2
21T R..8 Nm (0.8 m · kg, 5.8 ft · lb)
5. Install:
O-ring 1
Dowel pin 2
Oil hose 3
Bolt (oil hose) 4
NOTE:
Apply the lithium soap base grease on the O-
ring.
6. Install:
Spring 1
Pin 2
O-ring 3
Neutral switch 4
Screw (neutral switch) 5
NOTE:
Apply the lithium soap base grease on the O-
ring.
New
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
New
T R..4 Nm (0.4 m · kg, 2.9 ft · lb)

4 - 86
ENGCRANKCASE AND CRANKSHAFT
Extent of removal Order Part name Q’ty Remarks
10 Oil strainer 1
11 Oil delivery pipe 2 1
12 Crankshaft 1 Use special tool.
Refer to “REMOVAL POINTS”.
2

4 - 87
ENGCRANKCASE AND CRANKSHAFT
CRANKCASE BEARING
Extent of removal:1 Crankcase bearing removal
Extent of removal Order Part name Q’ty Remarks
CRANKCASE BEARING
REMOVAL
Preparation for removal Transmission
Shift cam and shift forkRefer to “TRANSMISSION, SHIFT
CAM AND SHIFT FORK” section.
1 Oil seal 3
2 Bearing 10 Refer to “REMOVAL POINTS”.
1

4 - 89
ENGCRANKCASE AND CRANKSHAFT
Crankshaft
1. Remove:
Crankshaft 1
Use the crankcase separating tool 2.
CAUTION:
Do not use a hammer to drive out the
crankshaft.
Crankshaft bearing
1. Remove:
Bearing 1
NOTE:
Remove the bearing from the crankcase by
pressing its inner race.
Do not use the removed bearing.
Crankcase separating tool:
YU-1135-A/90890-01135
INSPECTION
Timing chain and timing chain guide
1. Inspect:
Timing chain
Cracks/stiff → Replace the timing chain
and camshaft sprocket as a set.
2. Inspect:
Timing chain guide
Wear/damage → Replace.
EC4N4101
Crankcase
1. Inspect:
Contacting surface a
Scratches → Replace.
Engine mounting boss b, crankcase
Cracks/damage → Replace.
2. Inspect:
Bearing
Rotate inner race with a finger.
Rough spot/seizure → Replace.
3. Inspect:
Oil seal
Wear/damage → Replace.

4 - 90
ENGCRANKCASE AND CRANKSHAFT
EC4N4201
Crankshaft
1. Measure:
Runout limit a
Small end free play limit b
Connecting rod big end side clearance
c
Crank width d
Out of specification → Replace.
Use the dial gauge and a thickness
gauge.
Dial gauge and stand:
YU-3097/90890-01252
Standard
Runout
limit:0.03 mm
(0.0012 in)0.05 mm
(0.002 in)
Small end
free play:0.4 ~ 1.0 mm
(0.016 ~ 0.039 in)2.0 mm
(0.08 in)
Side
clearance:0.15 ~ 0.45 mm
(0.0059 ~ 0.0177 in)0.50 mm
(0.02 in)
Crack
width:61.95 ~ 62.00 mm
(2.439 ~ 2.441 in)—
Oil strainer
1. Inspect:
Oil strainer
Damage → Replace.
Oil delivery pipe
1. Inspect:
Oil delivery pipe
Cracks/damage → Replace.
Oil delivery pipe holes 1
Clogged → Blow out with compressed
air.