2016 YAMAHA WR 450F Owners Manual

VALVES AND VALVE SPRINGS
6-30
5. To fasten the valve cotters onto the valve stem, lightly tap the valve tip with a soft-face
hammer.
ECA
NOTICE
Hitting the valve tip with excessive force
could damage the valve.
6. Lubricate:
• Adjusting pad “1”
• Valve lifter “2”
7. Install: • Adjusting pad
• Valve lifter
TIP
• Check that the valve lifter turns smoothly when rotated with your finger.
• Make sure that the valve lifter and the adjust- ing pad are reinstalled in their original posi-
tions.
E
1
2

CYLINDER AND PISTON
6-31
EAS2GC1256
CYLINDER AND PISTON
Removing the cylinder and piston
OrderPart name Q’tyRemarks
Cylinder head Refer to “CYLINDER HEAD” on page 6-18.
1 Cylinder body
1
2 Gaskets
1
3 Dowel pin
2
4 Piston pin clip
2
5 Piston pin
1
6 Piston
1
7 Piston ring set
1
For installation, reverse the removal proce-
dure.
1
2
3
4
4
5
6
7
10 Nm (1.0 m kgf, 7.2 ft Ibf)T.R.
10 Nm (1.0 m kgf, 7.2 ft Ibf)T.R.
E
E
New
New
New
LT

CYLINDER AND PISTON
6-32
EAS2GC1257REMOVING THE PISTON
1. Remove:• Piston pin clips “1”
• Piston pin “2”
• Piston “3”
ECA13810
NOTICE
Do not use a hammer to drive the piston pin
out.
TIP
• Before removing the piston pin clip, cover the crankcase opening with a cloth to prevent the
piston pin clip from falling into the crankcase.
• Before removing the piston pin, deburr the piston pin clip’s groove and the piston pin’s
bore area. If the piston pin groove is deburred
and the piston pin is still difficult to remove,
use the piston pin puller set “4”.
2. Remove: • Top ring
• 2nd ring
• Oil ring
TIP
When removing a piston ring, open the end gap
with your fingers and lift the opposite end gap
of the piston ring over the piston crown.
EAS2GC1258CHECKING THE CYLINDER AND PISTON
1. Check:• Piston wall (Sidewall)
• Cylinder wall
Vertical scratches  Replace the cylinder,
and replace the piston and piston rings as a
set.
2. Measure: • Piston-to-cylinder clearance
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Measure the cylinder bore with the cylinder
bore gauge.
TIP
Measure cylinder bore by taking side-to-side
and front-to-back measurements of the cylin-
der.
Piston pin puller set
90890-01304
Piston pin puller YU-01304
1
Bore 97.000–97.010 mm (3.8189–
3.8193 in)
Taper limit 0.050 mm (0.0020 in)
Out of round limit 0.050 mm (0.0020 in)
Cylinder bore = maximum of D
1, D2, D3, D4,
D
5, D6
Taper limit (front-to-back) = maximum differ-
ence between D
1, D3, D5Taper limit (side-to-side) = maximum differ-
ence between D
2, D4, D6
Out of round limit (top) = difference between
D
1, D2Out of round limit (middle) = difference be-
tween D
3, D4Out of round limit (bottom) = difference be-
tween D
5, D6

CYLINDER AND PISTON
6-33
b. If out of specification, rebore or replace the cylinder, and replace the piston and the pis-
ton rings as a set.
c. Measure the piston outside diameter “a” at the measuring point (from piston skirt bot-
tom) “b” with the micrometer.
d. If out of specification, replace the cylinder, the piston, and the piston rings as a set.
e. Calculate the piston-to-cylinder clearance
with the following formula.
f. If out of specification, replace the cylinder, the piston, and the piston rings as a set.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EAS2GC1259CHECKING THE PISTON RINGS
1. Measure:• Piston ring side clearanceOut of specification  Replace the piston
and piston rings as a set.
TIP
Before measuring the piston ring side clear-
ance, eliminate any carbon deposits from the
piston ring grooves and piston rings.
2. Install: • Piston rings
TIP
Level the piston ring into the cylinder with the
piston.
Diameter
96.955–96.970 mm (3.8171–
3.8177 in)
Measuring point (from piston
skirt bottom) 9.0 mm (0.35 in)
Piston-to-cylinder clearance =
Cylinder bore - Piston diameter Piston-to-cylinder clearance0.030–0.055 mm (0.0012–0.0022
in)
Limit 0.15 mm (0.006 in)
b a
Ring side clearance
Top ring 0.015–0.065 mm (0.0006–0.0026
in)
Limit 0.120 mm (0.0047 in)
2nd ring 0.020–0.060 mm (0.0008–0.0024
in)
Limit 0.120 mm (0.0047 in)
a. 10 mm (0.39 in)

CYLINDER AND PISTON
6-34
3. Measure:• Piston ring end gapOut of specification  Replace the piston
ring.
TIP
The oil ring expander’s end gap cannot be
measured. If the oil ring ra il’s gap is excessive,
replace all three oil rings.
EAS2GC1260CHECKING THE PISTON PIN
1. Check:
• Piston pinBlue discoloration/grooves  Replace the
piston pin and then check the lubrication
system.
2. Measure: • Piston pin outside diameter “a”
Out of specification  Replace the piston
pin. 3. Measure:
• Piston pin bore inside diameter “b”Out of specification  Replace the piston.
EAS2GC1261INSTALLING THE PISTON AND CYLINDER
1. Install:
• Oil ring expander “1”
• Lower oil ring rail “2”
• Upper oil ring rail “3”
• 2nd ring “4”
• Top ring “5”
TIP
Be sure to install the piston rings so that the
manufacturer’s marks or numbers face up.
Piston ring
Top ring
End gap (installed)0.20–0.30 mm (0.0079–0.0118 in)
Limit 0.55 mm (0.0217 in)
2nd ring End gap (installed)0.35–0.50 mm (0.0138–0.0197 in)
Limit 0.85 mm (0.0335 in)
Oil ring End gap (installed)0.20–0.50 mm (0.0079–0.0197 in)
Piston pin outside diameter 17.991–18.000 mm (0.7083–
0.7087 in)
Limit 17.971 mm (0.7075 in)
Piston pin bore inside diameter 18.004–18.015 mm (0.7088–
0.7093 in)
Limit 18.045 mm (0.7104 in)
b

CYLINDER AND PISTON
6-35
2. Install:• Piston “1”
• Piston pin “2”
• Piston pin clips “3”
TIP
• Apply molybdenum disulfide oil to the piston pin.
• Install the piston with the F mark “a” on it pointing to its intake (front) side.
• Before installing the piston pin clip, cover the crankcase opening with a cloth to prevent the
clip from falling into the crankcase.
3. Lubricate: •Piston
• Piston rings
• Cylinder
4. Offset:
• Piston ring end gap 5. Install:
• Cylinder gasket
• Dowel pin
• Cylinder
TIP
• While compressing the piston rings with one hand, install the cylinder with the other hand.
• Pass the timing chain and timing chain guide
(exhaust side) through the timing chain cavity.
a. Top ring
b. 2nd ring
c. Upper oil ring rail
d. Oil ring expander
e. Lower oil ring rail
New
1
3
2
a
3
ac
eb
d
15
Ã
15Ã
15Ã
15Ã
15Ã
Cylinder bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
New
T R..

ELECTRIC STARTER
6-36
EAS2GC1262
ELECTRIC STARTER
Removing the starter motor
OrderJob/Parts to remove Q’tyRemarks
Exhaust pipe Refer to “ENGINE REMOVAL” on page 6-1.
1 Starter motor cover 1
2 Starter motor lead 1
3 Starter motor 1
For assembly, reverse the disassemble pro-
cedure.
1
12 Nm (1.2 m kgf, 8.7 ft Ibf)T.R.
2
3

ELECTRIC STARTER
6-37
Disassembling the starter motor
OrderJob/Parts to remove Q’tyRemarks
1 Starter motor front cover 1
2 Starter motor yoke 1
3 Armature assembly 1
4 Starter motor rear cover 1
5 Brush set 2
For assembly, reverse the disassembly pro-
cedure.