2016 YAMAHA WR 250F check oil

VALVES AND VALVE SPRINGS
6-28
EAS2GB7254CHECKING THE VALVE LIFTERS
1. Check:
• Valve lifter
Damage/scratches  Replace the valve lift-
ers and cylinder head.
EAS2GB7255INSTALLING THE VALVES
1. Clean:
• Valve stem end
2. Lubricate:
• Valve stem “1”
• Valve stem seal “2”3. Install:
• Spring seat “1”
• Valve stem seal “2”
•Valve “3”
• Valve spring “4”
• Valve spring retainer “5”
(to the cylinder head)
TIP
• Make sure each valve is installed in its original
place.
• Install the valve springs with the larger pitch
“a” facing up.
4. Install:
• Valve cotter “1”
TIP
Install the valve cotters by compressing the
valve spring with the valve spring compressor
“2” and the valve spring compressor adapter
“3”.
Recommended lubricant
Molybdenum disulfide oil
b. Smaller pitch
Valve spring compressor
90890-04019
Valve spring compressor
YM-04019
Valve spring compressor attach-
ment
90890-04108
Valve spring compressor adapter
22 mm
YM-04108
New

CYLINDER AND PISTON
6-31
EAS2GB7257REMOVING THE PISTON
1. Remove:
• Piston pin clip “1”
• Piston pin “2”
• Piston “3”
ECA
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
• 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.
EAS2GB7258CHECKING 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
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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
77.000–77.010 mm (3.0315–
3.0319 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
6-32
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.
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EAS2GB7259
CHECKING THE PISTON RINGS
1. Measure:
• Piston ring side clearance
Out 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.
3. Measure:
• Piston ring end gap
Out of specification  Replace the piston
ring.
TIP
The oil ring expander’s end gap cannot be
measured. If the oil ring rail’s gap is excessive,
replace all three oil rings. Diameter
76.955–76.970 mm (3.0297–
3.0303 in)
Measuring point (from piston
skirt bottom)
6.0 mm (0.24 in)
Piston-to-cylinder clearance =
Cylinder bore - Piston diameter
Piston-to-cylinder clearance
0.030–0.055 mm (0.0012–0.0022
in)
Limit
0.15 mm (0.006 in)
b
a
Ring side clearance
0.030–0.065 mm (0.0012–0.0026
in)
Limit
0.120 mm (0.0047 in)
a. 10 mm (0.39 in)

CYLINDER AND PISTON
6-33
EAS2GB7260CHECKING THE PISTON PIN
1. Check:
• Piston pin
Blue 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.EAS2GB7261INSTALLING THE PISTON AND CYLINDER
1. Install:
• Oil ring expander “1”
• Lower oil ring rail “2”
• Upper oil ring rail “3”
• Top ring “4”
TIP
Be sure to install the piston ring so that the
manufacturer’s marks or numbers face up.
2. Install:
• Piston “1”
• Piston pin “2”
• Piston pin clip “3” Piston ring
Top ring
End gap (installed)
0.15–0.25 mm (0.0059–0.0098 in)
Limit
0.50 mm (0.0197 in)
Oil ring
End gap (installed)
0.10–0.35 mm (0.0039–0.0138 in)
Piston pin outside diameter
15.991–16.000 mm (0.6296–
0.6299 in)
Limit
15.971 mm (0.6288 in)
Piston pin bore inside diameter
16.002–16.013 mm (0.6300–
0.6304 in)
Limit
16.043 mm (0.6316 in)
b
4
New

ELECTRIC STARTER
6-37
EAS2GB7263CHECKING THE STARTER MOTOR
1. Check:
•Commutator
Dirt  Clean with 600 grit sandpaper.
2. Measure:
• Commutator diameter “a”
Out of specification  Replace the starter
motor.
3. Measure:
• Mica undercut “a”
Out of specification  Scrape the mica to
the proper measurement with a hacksaw
blade that has been grounded to fit the com-
mutator.
TIP
The mica of the commutator must be undercut
to ensure proper operation of the commutator.
4. Measure:
• Armature assembly resistances (commuta-
tor and insulation)
Out of specification  Replace the starter
motor.
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a. Measure the armature assembly resistanc-
es with the pocket tester.
b. If any resistance is out of specification, re-
place the starter motor.
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5. Measure:
• Brush length “a”
Out of specification  Replace the brush
set.
6. Measure:
• Brush spring force
Out of specification  Replace the brush
set. Limit
16.6 mm (0.65 in)
Mica undercut (depth)
1.50 mm (0.06 in)
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
Armature coil
Commutator resistance “1”
0.0189–0.0231 
Insulation resistance “2”
Above 1 M
Limit
3.50 mm (0.14 in)
Brush spring force
3.92–5.88 N (400–600 gf, 14.11–
21.17 oz)

ELECTRIC STARTER
6-38
7. Check:
• Gear teeth
Damage/wear  Replace the starter motor.
8. Check:
• Oil seal
Damage/wear  Replace the defective part
(s).
EAS2GB7264ASSEMBLING THE STARTER MOTOR
1. Install:
• Brush spring “1”
• Brush “2”
2. Install:
• Armature assembly “1”
Install while holding down the brush using a
thin screw driver.
ECA
NOTICE
Be careful not to damage the brush during
installation.
3. Install:
• O-ring “1”
• Starter motor yoke “2”
ECA
NOTICE
Install the part that has a smaller step differ-
ence “a” with the magnet of the starter mo-
tor yoke facing the starter motor front
cover.
TIP
Align the match mark “a” on the starter motor
yoke with the match mark “b” on the starter mo-
tor rear cover.
4. Install:
• Circlip
•Plain washer “1”
• O-ring “2”
• Washer (starter motor front cover) “3”
• Starter motor front cover “4”
TIP
• For installation, align the projections on the
washer with the slots in the front cover.
• Align the match mark “a” on the starter motor
yoke with the match mark “b” on the starter
motor front cover.
New
ab
New

CLUTCH
6-45
EAS2GB7276CHECKING THE PRIMARY DRIVEN GEAR
1. Check:
• Primary driven gear
Damage/wear  Replace the primary drive
and primary driven gears as a set.
Excessive noise during operation  Re-
place the primary drive and primary driven
gears as a set.
EAS2GB7277INSTALLING THE OIL SEAL
1. Install:
• Oil seal “1”
• Washer “2”
• Circlip “3”
TIP
• Apply the lithium-soap-based grease on the
oil seal lip.
• Install the oil seal in parallel with its manufac-
ture's marks or numbers facing inward.
EAS2GB7278INSTALLING THE RIGHT CRANKCASE
COVER
1. Install:
• Dowel pin “1”
• O-ring “2”
• Collar “3”
• Gasket “4”
TIP
Apply the lithium-soap-based grease on the O-
ring.
2. Install:
• Right crankcase cover “1”• Right crankcase cover bolt “2”
TIP
• Apply the engine oil on the impeller shaft end.
• Mesh the impeller shaft gear “3” with primary
drive gear “4”.
• Tighten the right crankcase cover bolts in
stages and in a crisscross pattern.
EAS2GB7279INSTALLING THE CLUTCH
1. Install:
• Push lever shaft “1”
TIP
• Apply the lithium-soap-based grease on the
oil seal lip.
• Before installation, apply the engine oil to the
push lever shaft sliding surface.
New
New
3
2
1
LS
New
New
1
1
3
2
4
LS
Right crankcase cover bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
T R..
3
1
4
E
1
2

KICKSTATER
6-50
EAS2GB7282REMOVING THE KICK SHAFT ASSEMBLY
1. Remove:
• Kick shaft assembly “1”
TIP
Unhook the torsion spring “2” from the hole “a”
in the crankcase.
EAS2GB7283CHECKING THE KICK SHAFT AND RATCH-
ET WHEEL
1. Check:
• Ratchet wheel “1” smooth movement
Unsmooth movement  Replace.
• Kick shaft “2”
Wear/damage  Replace the kick shaft as-
sembly.
• Spring “3”
Broken  Replace.
EAS2GB7284CHECKING THE KICK GEAR, KICK IDLE
GEAR AND RATCHET WHEEL
1. Check:
• Kick gear “1”
Wear/damage  Replace the kick shaft as-
sembly.
• Kick idle gear “2”
• Ratchet wheel “3”
• Gear teeth “a”
• Ratchet teeth “b”
Wear/damage  Replace.
EAS2GB7285INSTALLING THE KICK SHAFT ASSEMBLY
1. Install:
• Kick gear “1”
• Washer “2”
• Circlip “3”
• Ratchet wheel “4”
• Spring “5”
• Washer “6”
• Circlip “7”
(to the kick shaft “8”)
TIP
• Apply molybdenum disulfide oil to the inner
circumferences of the kick gear and ratchet
wheel.
• Align the punch mark “a” on the ratchet wheel
with the punch mark “b” on the kick shaft.
2. Install:
• Torsion spring “1”
(to the kick shaft “2”)
TIP
Make sure the stopper “a” of the torsion spring
fits into the hole “b” on the kick shaft.
31
2
a
b
3
12
New
New