head YAMAHA WR 450F 2003 Owner's Guide

4 - 31
ENG

CYLINDER HEAD
ASSEMBLY AND INSTALLATION
1. Install:

Timing chain guide (front)
1

Dowel pin
2

Cylinder head gasket
3


Cylinder head
4
NOTE:

While pulling up the timing chain, install the
timing chain guide (front) and cylinder head.
New

2. Install:

Plain washer
1

Bolt [L=160 mm (6.30 in)]
2

Bolt [L=150 mm (5.91 in)]
3
Installation steps:
CAUTION:

Tighten the cylinder head using the rota-
tion angle procedure to obtain uniform
tightening torque.

Wash the threads and contact surfaces of
the bolts, the contact surfaces of the plain
washers, the contact surface of the cylin-
der head, and the threads of the crank-
case.

Apply the molybdenum disulfide grease on
the threads and contact surfaces of the
bolts and on both contact surfaces of the
plain washers.

Install the plain washers and bolts.

Tighten the bolts to the specified torque in
two or three steps in the proper tightening
sequence as shown.
T R..

Bolts (cylinder head):
1st:
30 Nm (3.0 m • kg, 22 ft • lb)

4 - 32
ENG


Remove the bolts.

Again apply the molybdenum disulfide
grease on the threads and contact sur-
faces of the bolts and on both contact sur-
faces of the plain washers.

Retighten the bolts.
NOTE:

Tighten the bolts to the specified torque in
two or three steps in the proper tightening
sequence as shown.
T R..

Bolts (cylinder head):
2nd:
20 Nm (2.0 m • kg, 14 ft • lb)

Put a mark on the corner
1
of the bolt
(cylinder head) and the cylinder head
2
as shown.
NOTE:

Tighten the bolts 90˚ in each of the two
steps to reach the specified angle of 180˚ in
the proper tightening sequence as shown.
T R..

Bolts (cylinder head):
Final:
Specified angle 180˚
1
2
180˚

3. Install:

Nut (cylinder head)
1
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)

4. Install:

Copper washer
1


Oil delivery pipe
2

Union bolt (M8)
3


Union bolt (M10)
4
New
T R..18 Nm (1.8 m · kg, 13 ft · lb)
T R..20 Nm (2.0 m · kg, 14 ft · lb)

CYLINDER HEAD

4 - 33
ENG

VALVES AND VALVE SPRINGS
VALVES AND VALVE SPRINGS
VALVES AND VALVE SPRINGS
Extent of removal:
1
Valve removal
Extent of removal Order Part name Q’ty Remarks
VALVES AND VALVE SPRINGS
REMOVAL
Preparation for removal Cylinder head Refer to “CYLINDER HEAD” section.
1 Valve lifter 5
Use special tool.
Refer to “REMOVAL POINTS”. 2 Adjusting pad 5
3 Valve cotter 10
4 Valve retainer 5
5 Valve spring 5
6 Stem seal 5
7 Valve spring seat 5
8 Exhaust valve 2
9 Intake valve 3
1

4 - 34
ENG

VALVES AND VALVE SPRINGS
REMOVAL POINTS
1. Remove:

Valve lifters
1


Pads
2

NOTE:

Identify each lifter
1
and pad
2
position very
carefully so that they can be reinstalled in their
original place.
2. Check:

Valve sealing
Leakage at the valve seat
→
Inspect
the valve face, valve seat and valve
seat width.
Checking steps:

Pour a clean solvent
1
into the intake and
exhaust ports.

Check that the valve seals properly.
There should be no leakage at the valve
seat
2
.
3. Remove:

Valve cotters
NOTE:
Attach a valve spring compressor 1 between
the valve spring retainer and the cylinder head
to remove the valve cotters.
Valve spring compressor:
YM-4019/90890-04019

4 - 35
ENGVALVES AND VALVE SPRINGS
INSPECTION
Valve
1. Measure:
Stem-to-guide clearance
Out of specification → Replace the
valve guide. Stem-to-guide clearance =
valve guide inside diameter a –
valve stem diameter b
Clearance (stem to guide):
Intake:
0.010 ~ 0.037 mm
(0.0004 ~ 0.0015 in)
: 0.08 mm (0.003 in)
Exhaust:
0.020 ~ 0.047 mm
(0.0008 ~ 0.0019 in)
: 0.10 mm (0.004 in)
2. Replace:
Valve guide
Replacement steps:
NOTE:
To ease guide removal, installation and to
maintain correct fit heat the cylinder head in
an over to 100 ˚C (212 ˚F).
Remove the valve guide using a valve
guide remover 1.
Install the new valve guide using a valve
guide remover 1 and valve guide installer
2.
After installing the valve guide, bore the
valve guide using a valve guide reamer 3
to obtain proper stem-to-guide clearance.

4 - 37
ENGVALVES AND VALVE SPRINGS
5. Measure:
Runout (valve stem)
Out of specification → Replace.
NOTE:
When installing a new valve always replace
the guide.
If the valve is removed or replaced always
replace the oil seal.
6. Eliminate:
Carbon deposits
(from the valve face and valve seat)
7. Inspect:
Valve seats
Pitting/wear → Reface the valve seat.
Runout limit:
0.01 mm (0.0004 in)
8. Measure:
Valve seat width a
Out of specification → Reface the valve
seat.
Valve seat width:
Intake:
0.9 ~ 1.1 mm (0.0354 ~ 0.0433 in)
: 1.6 mm (0.0630 in)
Exhaust:
0.9 ~ 1.1 mm (0.0354 ~ 0.0433 in)
: 1.6 mm (0.0630 in)
Measurement steps:
Apply Mechanic’s blueing dye (Dykem) b
to the valve face.
Install the valve into the cylinder head.
Press the valve through the valve guide
and onto the valve seat to make a clear
pattern.
Measure the valve seat width. Where the
valve seat and valve face made contact,
blueing will have been removed.
If the valve seat is too wide, too narrow, or
the seat is not centered, the valve seat
must be refaced.

4 - 38
ENGVALVES AND VALVE SPRINGS
9. Lap:
Valve face
Valve seat
NOTE:
After refacing the valve seat or replacing the
valve and valve guide, the valve seat and
valve face should be lapped.
Lapping steps:
Apply a coarse lapping compound to the
valve face.
CAUTION:
Do not let the compound enter the gap
between the valve stem and the guide.
Apply molybdenum disulfide oil to the
valve stem.
Install the valve into the cylinder head.
Turn the valve until the valve face and
valve seat are evenly polished, then clean
off all of the compound.
NOTE:
For best lapping results, lightly tap the valve
seat while rotating the valve back and forth
between your hands.
Apply a fine lapping compound to the
valve face and repeat the above steps.
NOTE:
After every lapping operation be sure to
clean off all of the compound from the valve
face and valve seat.
Apply Mechanic’s blueing dye (Dykem) to
the valve face.
Install the valve into the cylinder head.
Press the valve through the valve guide
and onto the valve seat to make a clear
pattern.
Measure the valve seat width again. If the
valve seat width is out of specification,
reface and relap the valve seat.

4 - 39
ENGVALVES AND VALVE SPRINGS
Valve spring
1. Measure:
Valve spring free length a
Out of specification → Replace.
2. Measure:
Compressed spring force a
Out of specification → Replace.
bInstalled length
Free length (valve spring):
Intake:
37.03 mm (1.46 in)
: 35.17 mm (1.38 in)
Exhaust:
37.68 mm (1.48 in)
: 35.79 mm (1.41 in)
Compressed spring force:
Intake:
111.3 ~ 127.9 N at 27.87 mm
(11.3 ~ 13.0 kg at 27.87 mm,
24.91 ~ 28.66 lb at 1.10 in)
Exhaust:
127.4 ~ 146.4 N at 27.38 mm
(13.0 ~ 14.9 kg at 27.38 mm,
28.66 ~ 32.85 lb at 1.08 in)
3. Measure:
Spring tilt a
Out of specification → Replace.
Spring tilt limit:
Intake:
2.5˚/1.61 mm (0.063 in)
Exhaust:
2.5˚/1.65 mm (0.065 in)
Valve lifter
1. Inspect:
Valve lifter
Scratches/damage → Replace both lift-
ers and cylinder head.

4 - 40
ENGVALVES AND VALVE SPRINGS
Combination of cylinder head and valve
lifter
1. Combination:
For this combination, match the paint
color on the cylinder head with that on the
valve lifter according to the chart below.
NOTE:
When you purchase a cylinder head, you can-
not designate its size. Choose the valve lifter
that matches the above chart.Combination
Cylinder head mark
a (color)Valve lifter mark
b (color)
Blue Blue
Yellow Yellow
Purple Black
ab
ASSEMBLY AND INSTALLATION
1. Apply:
Molybdenum disulfide oil
Onto the valve stem and valve stem
seal.
2. Install:
Valves 1
Valve spring seats 2
Valve stem seals 3
Valve springs 4
Valve spring retainers 5
NOTE:
Make sure that each valve is installed in its
original place, also referring to the painted
color as follows.
Intake (middle) a: blue
Intake (right/left) b: gray
Exhaust: not paint
Install the valve springs with the larger pitch
c facing upward.
dSmaller pitch
New

4 - 42
ENGCYLINDER AND PISTON
CYLINDER AND PISTON
CYLINDER AND PISTON
Extent of removal:1 Cylinder removal2 Piston removal
Extent of removal Order Part name Q’ty Remarks
CYLINDER AND PISTON
REMOVAL
Preparation for removal Cylinder head Refer to “CYLINDER HEAD” section.
1 Bolt (cylinder) 1
2 Cylinder 1
3 Gasket 1
4 Dowel pin 2
5 Dowel pin/O-ring 1/1
6 Piston pin clip 2
Use special tool.
Refer to “REMOVAL POINTS”. 7 Piston pin 1
8 Piston 1
9 Piston ring set 1
2
1