engine YAMAHA YZ250F 2009 Workshop Manual

4-38
BALANCER
REMOVING THE BALANCER
1. Straighten the lock washer tab.
2. Loosen:
• Nut (primary drive gear) "1"
• Nut (balancer shaft driven gear)
"2"
Place an aluminum plate "a" between
the teeth of the balancer shaft drive
gear "3" and driven gear "4".
3. Remove:
• Balancer shaft "1"
When removing the balancer shaft,
align the center "a" of the balancer
shaft weight along the line connecting
the centers of the crankshaft and bal-
ancer shaft.
CHECKING THE PRIMARY DRIVE
GEAR, BALANCER SHAFT DRIVE
GEAR AND BALANCER SHAFT
DRIVEN GEAR
1. Inspect:
• Primary drive gear "1"
• Balancer shaft drive gear "2"
• Balancer shaft driven gear "3"
Wear/damage→Replace.CHECKING THE BALANCER
SHAFT
1. Inspect:
• Balancer shaft
Cracks/damage→Replace.
INSTALLING THE BALANCER
1. Install:
• Balancer shaft "1"
• Apply the engine oil on the bearing.
• When installing the balancer shaft,
align the center "a" of the balancer
shaft weight along the line connect-
ing the centers of the crankshaft
and balancer shaft.
2. Install:
• Balancer shaft driven gear "1"
Install the balancer shaft driven gear
onto the balancer shaft while aligning
the punch mark "a" on the balancer
shaft driven gear with the lower spline
"b" on the balancer shaft end.
3. Install:
• Balancer shaft drive gear "1"
• Align the punched mark "a" on the
balancer shaft drive gear with the
punched mark "b" on the balancer
shaft driven gear "2".
• Align the punched mark "c" on the
balancer shaft drive gear with the
lower spline "d" on the crankshaft
end.
4. Install:
• Lock washer "1"
• Nut (balancer shaft driven gear)
"2"
• Primary drive gear "3"
• Lock washer "4"
• Nut (primary drive gear) "5"
• Install the primary drive gear with its
stepped side "a" facing the engine.
• Place an aluminum plate "b" be-
tween the teeth of the balancer
shaft drive gear "6" and driven gear
"7".
5. Bend the lock washer tab.
Nut (balancer shaft driv-
en gear):
50 Nm (5.0 m•kg, 36
ft•lb)
Nut (primary drive gear):
75 Nm (7.5 m•kg, 54
ft•lb)

4-40
OIL PUMP
REMOVING THE OIL TANK
Order Part name Q'ty Remarks
Drain the engine oil.Refer to "CHANGING THE ENGINE OIL"
section in the CHAPTER 3.
1Oil hose 2 1
2Oil hose 1 1
3 Dowel pin 2
4 Oil tank breather hose 1
5 Oil tank 1
6 Oil strainer 1

4-41
OIL PUMP
CHECKING THE OIL PUMP
1. Inspect:
• Oil pump drive gear "1"
• Oil pump drive shaft "2"
• Rotor housing "3"
• Oil pump cover "4"
Cracks/wear/damage→Replace.
2. Measure:
• Tip clearance "a"
(between the inner rotor "1" and
outer rotor "2")
• Side clearance "b"
(between the outer rotor "2" and
rotor housing "3")
• Housing and rotor clearance "c"
(between the rotor housing "3"
and rotors "1" "2")
Out of specification→Replace the
oil pump assembly.3. Check:
• Unsmooth→Repeat steps #1 and
#2 or replace the defective parts.
INSTALLING THE OIL PUMP
1. Install:
• Oil pump drive shaft "1"
•Washer "2"
• Dowel pin "3"
• Inner rotor 1 "4"
• Apply the engine oil on the oil pump
drive shaft and inner rotor 1.
• Fit the dowel pin into the groove in
the inner rotor 1.
2. Install:
• Outer rotor 1 "1"
Apply the engine oil on the outer rotor
1.
3. Install:
• Oil pump cover "1"
• Screw (oil pump cover) "2"
• Dowel pin "3"
• Inner rotor 2 "4"
•Circlip "5"
• Apply the engine oil on the inner ro-
tor 2.
• Fit the dowel 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 = 25 mm (0.94 in)] "4"
• Bolt (oil pump assembly)
[L = 30 mm (1.18 in)] "5"
Apply the engine oil on the outer rotor
2.
5. Install:
• Oil pump drive gear "1"
• Washer "2"
• Circlip "3"
Apply the engine oil on the oil pump
drive gear inner circumference.
Tip clearance "a":
0.12 mm or less (0.0047
in or less)
<Limit>: 0.20 mm
(0.008 in)
Side clearance "b":
0.09–0.17 mm (0.0035–
0.0067 in)
<Limit>: 0.24 mm
(0.009 in)
Housing and rotor clear-
ance "c":
0.03–0.10 mm (0.0012–
0.0039 in)
<Limit>: 0.17 mm
(0.0067 in)
Screw (oil pump cover):
1.7 Nm (0.17 m•kg, 1.2
ft•lb)
Bolt (oil pump assem-
bly):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (oil pump assem-
bly):
10 Nm (1.0 m•kg, 7.2
ft•lb)

4-45
KICK SHAFT AND SHIFT SHAFT
INSTALLING THE SHIFT GUIDE
AND SHIFT LEVER ASSEMBLY
1. Install:
• Spring "1"
• Pawl pin "2"
•Pawl "3"
To shift lever "4".
Apply the engine oil on the spring,
pawl pin and pawl.
2. Install:
• Shift lever assembly "1"
To shift guide "2".
3. Install:
• Shift lever assembly "1"
• Shift guide "2"
• 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" INSTALLING THE SHIFT SHAFT
1. Install:
•Roller "1"
•Collar "2"
• Torsion spring "3"
• Shift shaft "4"
Apply the engine oil on the roller and
shift shaft.
2. Install:
• Shift pedal "1"
• Bolt (shift pedal) "2"
When installing the shift pedal onto
the shift shaft, be sure that the center
of the shift pedal is about 0 mm (0 in)
"a" above the top of the footrest.
INSTALLING THE KICK SHAFT
ASSEMBLY
1. Install:
• Kick gear "1"
•Washer "2"
•Circlip "3"
• Ratchet wheel "4"
• Spring "5"
•Washer "6"
•Circlip "7"
To kick shaft "8".
• Apply the molybdenum disulfide oil
on 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 kick shaft "2".
Make sure the stopper "a" of the tor-
sion spring fits into the hole "b" on the
kick shaft.
3. Install:
• Spring guide "1"
Slide the spring guide into the kick
shaft, make sure the groove "a" in the
spring guide fits on the stopper of the
torsion spring.
4. Install:
• Kick shaft assembly "1"
• Washer "2"
• Apply the molybdenum disulfide
grease on the contacting surfaces
of the kick shaft stopper "a" and kick
shaft ratchet wheel guide "3".
• Apply the engine oil on the kick
shaft.
• Slide the kick shaft assembly into
the crankcase and make sure the
kick shaft stopper "a" fits into the
kick shaft ratchet wheel guide.
Bolt (shift guide):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (shift pedal):
12 Nm (1.2 m•kg, 8.7
ft•lb)

4-46
KICK SHAFT AND SHIFT SHAFT
5. Hook:
• Torsion spring "1"
Turn the torsion spring clockwise and
hook into the proper hole "a" in the
crankcase.
INSTALLING THE KICK IDLE
GEAR
1. Install:
• Kick idle gear "1"
• Washer "2"
• Circlip "3"
• Apply the engine oil on the kick idle
gear inner circumference.
• Install the kick idle gear with its de-
pressed side "a" toward you.

4-49
ENGINE REMOVAL
ENGINE REMOVAL
REMOVING THE ENGINE
Order Part name Q'ty Remarks
Hold the machine by placing the suitable stand
under the frame.Refer to "HANDLING NOTE".
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 Disconnect at the engine side.
Radiator Refer to "RADIATOR" section.
Shift pedalRefer to "KICK SHAFT AND SHIFT SHAFT"
section.
Cylinder head breather hose Refer to "CAMSHAFTS" section.
Drain the engine oil.Refer to "CHANGING THE ENGINE OIL"
section in the CHAPTER 3.
Oil hose and oil tank breather hose Refer to "OIL PUMP" section.
Ignition coil
Disconnect the CDI magneto lead.
Right engine guard

4-50
ENGINE REMOVAL
1 Lower engine guard 1
2 Neutral switch 1
3 Drive chain sprocket cover 1
4 Nut (drive sprocket) 1 Refer to removal section.
5 Lock washer 1 Refer to removal section.
6 Drive sprocket 1 Refer to removal section.
7 Clip 1
8 Bolt (brake pedal) 1
9 Brake pedal 1
10 Upper engine bracket 2
11 Lower engine bracket 2
12 Engine mounting bolt 3
13 Pivot shaft 1 Refer to removal section.
14 Engine 1 Refer to removal section. Order Part name Q'ty Remarks

4-51
ENGINE REMOVAL
HANDLING NOTE
Support the machine securely so
there is no danger of it falling over.
REMOVING THE DRIVE
SPROCKET
1. Remove:
• Nut (drive sprocket) "1"
• Lock washer "2"
• Straighten the lock washer tab.
• Loosen the nut while applying the
rear brake.
2. Remove:
• Drive sprocket "1"
• Drive chain "2"
Remove the drive sprocket together
with the drive chain.
REMOVING THE ENGINE
1. Remove:
• Pivot shaft "1"
If the pivot shaft is pulled all the way
out, the swingarm will come loose. If
possible, insert a shaft of similar di-
ameter into the other side of the swin-
garm to support it.
2. Remove:
• Engine "1"
From right side.
Make sure that the couplers, hoses
and cables are disconnected.
INSTALLING THE ENGINE
1. Install:
•Engine "1"
Install the engine from right side.
• Pivot shaft "2"
• Engine mounting bolt (lower) "3"
• Lower engine bracket "4"
• Bolt (lower engine bracket) "5"
•Patch "6"
• Engine mounting bolt (front) "7"
• Upper engine bracket "8"
• Bolt (upper engine bracket) "9"
• Engine mounting bolt (upper) "10"
• Lower engine guard "11"
• Bolt (lower engine guard) "12"
• Apply the molybdenum disulfide
grease on the pivot shaft.
• Install the patch with the claw "a"
facing outside the chassis.
INSTALLING THE BRAKE PEDAL
1. Install:
• Spring "1"
• Brake pedal "2"
• O-ring "3"
• Bolt (brake pedal) "4"
•Clip "5"
Apply the lithium soap base grease
on the bolt, O-rings and brake pedal
bracket.
INSTALLING THE DRIVE
SPROCKET
1. Install:
• Drive sprocket "1"
• Drive chain "2"
Install the drive sprocket together
with the drive chain.
Pivot shaft:
85 Nm (8.5 m•kg, 61
ft•lb)
Engine mounting bolt
(lower):
53Nm (5.3 m•kg, 38
ft•lb)
Bolt (lower engine brack-
et):
34 Nm (3.4 m•kg, 24
ft•lb)
Engine mounting bolt
(front):
53 Nm (5.3 m•kg, 38
ft•lb)
Bolt (upper engine brack-
et):
34 Nm (3.4 m•kg, 24
ft•lb)
Engine mounting bolt
(upper):
55 Nm (5.5 m•kg, 40
ft•lb)
Bolt (lower engine
guard):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (brake pedal):
26 Nm (2.6 m•kg, 19
ft•lb)

4-52
ENGINE REMOVAL
2. Install:
• Lock washer "1"
• Nut (drive sprocket) "2"
Tighten the nut while applying the
rear brake.
3. Bend the lock washer tab to lock
the nut.
4. Install:
• Drive chain sprocket guide "1"
• Drive chain sprocket cover "2"
• Screw (drive chain sprocket cov-
er) "3"
INSTALLING THE NEUTRAL
SWITCH
1. Install:
• Spring "1"
•Pin "2"
• O-ring "3"
• Neutral switch "4"
• Screw (neutral switch) "5"
Apply the lithium soap base grease
on the O-ring.
2. Install:
• Hose guide (cylinder head breath-
er hose) "1"
• Bolt (hose guide) "2"
Nut (drive sprocket):
75 Nm (7.5 m•kg, 54
ft•lb)
Screw (drive chain
sprocket cover):
8 Nm (0.8 m•kg, 5.8
ft•lb)
Screw (neutral switch):
4 Nm (0.4 m•kg, 2.9
ft•lb)
Bolt (hose guide):
10 Nm (1.0 m•kg, 7.2
ft•lb)

4-53
CRANKCASE AND CRANKSHAFT
CRANKCASE AND CRANKSHAFT
REMOVING THE CRANKSHAFT
Order Part name Q'ty Remarks
Engine Refer to "ENGINE REMOVAL" section.
Piston Refer to "CYLINDER AND PISTON" section.
Kick shaft assemblyRefer to "KICK SHAFT AND SHIFT SHAFT"
section.
SegmentRefer to "KICK SHAFT AND SHIFT SHAFT"
section.
Stator Refer to "CDI MAGNETO" section.
Balancer shaft Refer to "BALANCER" section.
1 Timing chain guide (intake side) 1
2 Timing chain 1
3 Oil delivery pipe 2 1
4 Bolt [L = 45 mm (1.77 in)] 6 Refer to removal section.
5 Bolt [L = 55 mm (2.17 in)] 1 Refer to removal section.
6 Bolt [L = 70 mm (2.76 in)] 4 Refer to removal section.
7 Hose guide 1 Refer to removal section.
8 Clutch cable holder 1 Refer to removal section.
9 Right crankcase 1 Refer to removal section.