2015 YAMAHA WR 250F engine

OIL PUMP AND BALANCER GEAR
6-60
NOTICE
After tightening the bolts, make sure that
the oil pump turns smoothly.
2. Install:
• Collar “1”
• Balancer weight gear “2”
TIP
Install the balancer weight gear and balancer
shaft with their lower splines “a” aligning with
each other.
3. Install:
• Balancer drive gear “1”
• Collar “2”
TIP
• Align the punched mark “a” on the balancer
drive gear with the punched mark “b” on the
balancer weight gear.
• Install the balancer drive gear and crankshaft
with the lower splines “c” aligning with each
other.4. Install:
• Conical washer “1”
• Balancer weight gear nut “2”
• Primary drive gear “3”
• Conical washer “4”
• Primary drive gear nut “5”
•Balancer “6”
• Conical washer “7”
• Balancer nut “8”
TIP
• Apply engine oil to the contact surface and
threaded portion of the primary drive gear nut.
• Place an aluminum plate “a” between the
teeth of the balancer drive gear “9” and bal-
ancer weight gear “10”.
• Install the conical washer with its convex sur-
face “b” outward.
• Align the balancer flat portion “c” with the flat
portion “d”.
21
1
2
Balancer weight gear nut
50 Nm (5.0 m·kgf, 36 ft·lbf)
Primary drive gear nut
75 Nm (7.5 m·kgf, 54 ft·lbf)
Balancer nut
38 Nm (3.8 m·kgf, 27 ft·lbf)
New
T R..
New
T R..
New
T R..
a
210
b
2 91
b53
a41059
3
E

GENERATOR AND STARTER CLUTCH
6-62
EAS2GB2307
GENERATOR AND STARTER CLUTCH
Removing the generator
Order Job/Parts to remove Q’ty Remarks
Drain the engine oil.Refer to “CHANGING THE ENGINE OIL” on
page 3-17.
Seat and fuel tankRefer to “GENERAL CHASSIS” on page 5-1
and “FUEL TANK” on page 8-1.
Disconnect the AC magneto lead.
Clutch cable
Shift pedal Refer to “SHIFT SHAFT” on page 6-52.
1 Cover (Damper assembly) 1
2 Damper assembly 1
3 Breather hose 1
4 Left crankcase cover 1
5Gasket 1
6 Dowel pin 2
7 Starter idle gear 1
8 Bearing 1
9 Starter idle gear shaft 1
10 Generator rotor 1
T R..
T R..
6
611
9
8
7
2
3
1
14
4 5
12
10
13
T R..
T R..
T R..LTT R..
T R..
15

GENERATOR AND STARTER CLUTCH
6-65
EAS2GB2310INSTALLING THE STARTER CLUTCH
1. Install:
• Stator “1”
• Stator bolt “2”
• Crankshaft position sensor “3”
• Holder “4”
• Crankshaft position sensor bolt “5”
TIP
• Pass the AC magneto lead “6” and crankshaft
position sensor lead “7” under the holder as
shown.
• Tighten the stator bolt using the T25 bit.
• Apply the sealant to the grommet of the AC
magneto lead.
2. Install
• Starter clutch drive gear “1”
TIP
Apply the engine oil on the starter clutch drive
gear inner circumference.3. Install:
• Starter clutch “1”
To generator rotor “2”.
EAS2GB2311INSTALLING THE GENERATOR
1. Install:
• Woodruff key “1”
• Generator rotor “2”
TIP
• Clean the contact surfaces of the tapered por-
tions of the crankshaft and generator rotor.
• When installing the woodruff key, make sure
that its flat surface “a” is in parallel with the
crankshaft center line “b”.
• When installing the generator rotor, align the
keyway “c” of the generator rotor with the
woodruff key. Stator bolt
7 Nm (0.7 m·kgf, 5.1 ft·lbf)
LOCTITE®
Crankshaft position sensor bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
Yamaha bond No. 1215
90890-85505
(Three bond No.1215®)
T R..
T R..
6
7
1
3
22
5
5
4LT
Starter clutch bolt
16 Nm (1.6 m·kgf, 12 ft·lbf)
LOCTITE®
21
LT
T R..
2 C1 1
1a b

GENERATOR AND STARTER CLUTCH
6-66
2. Install:
• Washer
• Generator rotor nut “1”
TIP
Tighten the generator rotor nut to 65 Nm (6.5
m·kgf, 47 ft·lbf), loosen and retighten the gener-
ator rotor nut to 65 Nm (6.5 m·kgf, 47 ft·lbf).
3. Install:
• Starter idle gear shaft “1”
• Bearing “2”
• Starter idle gear 2 “3”
TIP
Apply the engine oil on the starter idle gear
shaft, bearing and idle gear inner circumfer-
ence.
4. Install:
• Dowel pin
• Crankcase cover gasket
• Left crankcase cover “1”
• Lead holder “2”
• Crankcase cover bolt
• Neutral switch lead “3”
TIP
• Pass the AC magneto lead “4” under the left
crankcase cover “a” as shown.
• Tighten the bolts in stage, using a crisscross
pattern.
5. Install:
• Washer “1”
• Damper assembly “2”
• Washer “3”
TIP
Apply the engine oil to the shaft and washers.
6. Install:
• Cover (damper assembly) “1”
• Bracket “2”
•Bolt “3”
• Breather hose 2 “4” Generator rotor nut
65 Nm (6.5 m·kgf, 47 ft·lbf)
Crankcase cover bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
T R..
1
1
21
2
3
New
T R..Bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
4
1a
1
2
3
21
2
3
T R..

CRANKCASE
6-68
EAS2GB2312
CRANKCASE
Separating the crankcase
Order Part name Q’ty Remarks
Engine Refer to “ENGINE REMOVAL” on page 6-1.
PistonRefer to “CYLINDER AND PISTON” on page
6-30.
BalancerRefer to “OIL PUMP AND BALANCER
GEAR” on page 6-56.
Kick shaft assembly Refer to “KICKSTATER” on page 6-49.
Segment Refer to “SHIFT SHAFT” on page 6-52.
Generator rotorRefer to “GENERATOR AND STARTER
CLUTCH” on page 6-62.
1 Timing chain guide (exhaust side) 1
2 Timing chain guide stopper plate 1
3 Timing chain 1
4 Bolt [L = 45 mm (1.77 in)] 7
5 Bolt [L = 60 mm (2.36 in)] 2
6 Bolt [L = 75 mm (2.95 in)] 3
7 Right crankcase 1
8 Left crankcase 1
9 Dowel pin 2
10 Nm (1.0 mkgf, 7.2 ftIbf)T.R
.
12 Nm (1.2 mkgf, 8.7 ftIbf)T.R
.
12 Nm (1.2 mkgf, 8.7 ftIbf)T.R
.
12 Nm (1.2 mkgf, 8.7 ftIbf)T.R
.
3
1 5
2
6410 56
4
4
446
9117
8
9
LT

CRANKCASE
6-71
EAS2GB2313DISASSEMBLING THE CRANKCASE
1. Separate:
• Right crankcase
• Left crankcase
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Remove the crankcase bolts.
TIP
Loosen each bolt 1/4 of a turn at a time and af-
ter all the bolts are loosened, remove them.
b. Remove the right crankcase “1”.
TIP
• Place the crankcase with its left side down-
ward and split it by inserting a screwdriver tip
into the splitting slit “a” in the crankcase.
• Lift the right crankcase horizontally while light-
ly patting the crankcase splitting slit and the
engine mounting boss using a soft hammer,
and leave the crankshaft and the transmission
with the left crankcase.
ECA
NOTICE
Use soft hammer to tap on the case half.
Tap only on reinforced portions of case. Do
not tap on gasket mating surface. Work
slowly and carefully. Make sure the case
halves separate evenly. If the cases do not
separate, check for a remaining case bolt or
fitting. Do not force.c. Remove the dowel pins and O-ring.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EAS2GB2314REMOVING THE CRANKCASE BEARING
1. Remove:
• Bearing “1”
TIP
• Remove the bearing from the crankcase by
pressing its inner race.
• Do not use the removed bearing.
EAS2GB2315CHECKING THE TIMING CHAIN, TIMING
CHAIN GUIDE, OIL STRAINER
1. Check:
• Timing chain
Stiffness  Replace the camshaft sprocket,
timing chain and crankshaft sprocket as a
set.
2. Check:
• Timing chain guide
Damage/wear  Replace
EAS2GB2316CHECKING THE CRANKCASE
1. Wash:
• Crankcase
TIP
• Wash the crankcase in a mild solvent.
• Remove any remaining gasket from the
crankcase mating surface.
2. Check:
• Crankcase
Crack/damage  Replace.
1
a

TRANSMISSION
6-76
EAS2GB2324
TRANSMISSION
Removing the transmission, shift drum assembly, and shift forks
Order Part name Q’ty Remarks
Engine Refer to “ENGINE REMOVAL” on page 6-1.
CrankcaseSeparate.
Refer to “CRANKCASE” on page 6-68.
1 Main axle 1
2 Drive axle 1
3 Long shift fork guide bar 1
4 Short shift fork guide bar 1
5Spring 4
6 Shift cam 1
7 Shift fork 3 (R) 1
8 Shift fork 2 (C) 1
9 Shift fork 1 (L) 1
10 Collar 1
For installation, reverse the removal proce-
dure.
2
10
1
53
4 578
69
M
M
M
M
M
EE
E
E
LS
New

TRANSMISSION
6-79
2. Install:
• 2nd wheel gear (29T) “1”
• 5th wheel gear (22T) “2”
• 3rd wheel gear (26T) “3”
• 4th wheel gear (24T) “4”
• 6th wheel gear (22T) “5”
• Collar “6”
• 1st wheel gear (31T) “7”
• O-ring “8”
(to the drive axle “9”)
TIP
• Before installation, apply molybdenum disul-
fide oil to the inner and end surface of the idler
gear and to the inner surface of the sliding
gear, then install.
• Apply the lithium-soap-based grease on the
O-ring.
3. Install:
• Washer “1”
• Circlip “2”
TIP
• Be sure the circlip sharp-edged corner “a” is
positioned opposite side to the washer and
gear “b”.
• Install the circlip with its ends “c” settled even-
ly on the spline crests.4. Install:
• Collar “1”
TIP
• Apply the lithium-soap-based grease on the
oil seal lip.
• When installing the collar into the crankcase,
pay careful attention to the crankcase oil seal
lip.
5. Install:
• Main axle “1”
• Drive axle “2”
TIP
• Install to the left crankcase simultaneously.
• Apply engine oil to the main axle and the drive
axle bearing.
New
891
234
567M
New
LS
M
New
21
2
ab
cc
1
2
EE