2014 YAMAHA YZ250F light

HANDLEBAR
4-35
6. Install:
• Right grip “1”
• Collar “2”
Apply adhesive to the tube guide “3”.
TIP
• Before applying the adhesive, wipe off grease
or oil on the tube guide surface “a” with a lac-
quer thinner.
• Install the grip to the tube guide so that the
grip match mark “b” and tube guide slot “c”
form the angle as shown.
7. Install:
• Collar “1”
• Rubber cover “2”
• Throttle grip “3”
TIP
Apply the lithium soap base grease on the
throttle grip sliding surface.8. Install:
• Throttle cables “1”
TIP
Slightly coat the end of throttle cable and inside
of throttle grip with lithium-soap-based grease.
Then, mount the throttle grip onto the handle-
bar.
9. Install:
• Throttle cable housings “1”
• Screw (throttle cable housings) “2”
EWA1DX5001
WARNING
After tightening the throttle cable housing
screws, check that the throttle grip “3”
moves smoothly. If it does not, retighten the
screws for adjustment.
1b
c
3
Screw (throttle cable housings)
3.8 Nm (0.38 m·kgf, 2.8 ft·lbf)
T R..

CAMSHAFT
5-15
c. Install the dowel pins and the camshaft
caps.
TIP
• Tighten the camshaft cap bolts in a crisscross
pattern from innermost to outer caps.
• Do not turn the camshaft when measuring the
camshaft journal-to-camshaft cap clearance.
d. Remove the camshaft caps and then mea-
sure the width of the Plastigauge® “1”.
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5. Measure:
• Camshaft journal diameter “a”
Out of specification  Replace the cam-
shaft.
Within specification  Replace the cylinder
head and the camshaft caps as a set.
EAS1SM1210CHECKING THE TIMING CHAIN AND CAM-
SHAFT SPROCKET
1. Check:
• Timing chain “1”
Damage/stiffness  Replace the timing
chain and camshaft and camshaft sprocket
as a set.2. Check:
• Camshaft sprocket
More than 1/4 tooth wear “a”  Replace the
camshaft sprocket and the timing chain as a
set.
EAS1SM1211CHECKING THE TIMING CHAIN TENSION-
ERS
1. Check:
• Timing chain tensioner
Crack/damage  Replace.
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a. While pressing the tensioner rod lightly with
your fingers, use a thin screwdriver “1” to
wind the tensioner rod up fully clockwise.
b. When releasing the screwdriver by pressing
lightly with your fingers, make sure that the
tensioner rod will come out smoothly.
c. If not, replace the tensioner assembly.
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Camshaft cap bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
Camshaft journal diameter
21.959–21.972 mm (0.8645–
0.8650 in)
T R..
1
a. 1/4 tooth
b. Correct
1. Timing chain roller
2. Camshaft sprocket
a
b1
2

CAMSHAFT
5-17
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2. Install:
• Timing chain tensioner
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a. While pressing the tensioner rod lightly with
your fingers, use a thin screwdriver to wind
the tensioner rod up fully clockwise.
b. With the tensioner rod fully wound and the
chain tensioner UP mark “a” facing upward,
install the gasket “1”, the timing chain ten-
sioner “2”, and the gasket “3”, and tighten
the bolt “4”.
c. Release the screwdriver, check that the ten-
sioner rod comes out smoothly, and tighten
the gasket “5” and the cap bolt “6”.
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3. Turn:
• Crankshaft
Counterclockwise several turns.
4. Check:
• Top dead center (TDC) mark on the rotor
Align with the crankcase alignment mark.
• Camshaft match marks
Align with the cylinder head surface.
Out of alignment  Adjust.
5. Install:
• Timing chain guide (top side) “1”
• Cylinder head cover gasket “2”
• Cylinder head cover “3”
• Bolt (cylinder head cover) “4”
TIP
Before installation, apply the sealant to the cyl-
inder head cover gasket.
6. Install:
• Cylinder head breather hose
• Spark plug Bolt (timing chain tensioner)
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
Tensioner cap bolt
6 Nm (0.6 m·kgf, 4.3 ft·lbf)
3
4
8
7
15
26
T R..
T R..
Bolt (cylinder head cover)
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
Three Bond No.1215®
90890-85505
Spark plug
13 Nm (1.3m·kgf, 9.4 ft·lbf)
6 5
T R..
4
4
3
21
T R..

VALVES AND VALVE SPRINGS
5-28
INSTALLING 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”.
5. To fasten the valve cotters onto the valve
stem, lightly tap the valve tip with a soft-face
hammer.
ECA13800
NOTICE
Hitting the valve tip with excessive force
could damage the valve. Recommended lubricant
Molybdenum disulfide oil
b. Smaller pitch
New
Valve spring compressor
90890-04019
YM-04019
Valve spring compressor adapter
22 mm
90890-04108
YM-04108

CRANKCASE
5-64
EAS1SM1278DISASSEMBLING THE CRANKCASE
1. Separate:
• Right crankcase
• Left crankcase
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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.
ECA33DD041
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.
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1. Remove:
• Bearing “1”
TIP
• Remove the bearing from the crankcase by
pressing its inner race.
• Do not use the removed bearing.
EAS1SM1280CHECKING 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
EAS1SM1281CHECKING 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.
• Oil delivery passages
Obstruction  Blow out with compressed
air.
1
a

CRANKCASE
5-65
EAS1SM1282INSTALLING THE OIL SEAL
1. Install:
• Oil seal “1”
(to left crankcase)
EAS1SM1283ASSEMBLING THE CRANKCASE
1. Install:
• Bearing cover plate screw
TIP
Install the bearing by pressing its outer race
parallel.
2. Apply:
• Sealant
(to the crankcase mating surface)
3. Install:
• Dowel pin “1”
• Crankcase (to the left crankcase)
TIP
• Apply the lithium-soap-based grease on the
O-ring.
• Fit the right crankcase onto the left crankcase.
Tap lightly on the case with soft hammer.
• When installing the crankcase, the connecting
rod should be positioned at top dead center
(TDC).
• Tighten the bolts in a crisscross pattern in two
(2) stages, with 1/4 turn each. Installed depth “a”
4.5–5.0 mm (0.18–0.20 in)
Bearing cover plate screw
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
LOCTITE®
Bearing cover plate screw (crank-
shaft)
22 Nm (2.2 m·kgf, 16 ft·lbf)
LOCTITE®
Three Bond No.1215®
90890-85505
New
a 1
T R..
Crankcase bolt
12 Nm (1.2 m·kgf, 8.7 ft·lbf)
3. 45 mm (1.77 in)
4. 60 mm (2.36 in)
5. 75 mm (2.95 in)
a. Hexagon socket head bolt without flange
b. Hexagon socket head bolt with flange
T R..
4
5
3
43
335 5 5
3
ab

TRANSMISSION
5-70
EAS1SM1290REMOVING THE TRANSMISSION
1. Remove:
• Long shift fork guide bar “1”
• Short shift fork guide bar “2”
• Shift cam “3”
• Shift fork 3 “4”
• Shift fork 2 “5”
• Shift fork 1 “6”
• Main axle “7”
• Drive axle “8”
• Collar “9”
TIP
• Remove assembly with the collar “9” installed
to the crankcase.
• Make a note of the position of each part. Pay
particular attention to the location and direc-
tion of shift forks.
• Remove the main axle and the drive axle all
together by tapping the drive axle lightly with
a soft hammer.
EAS1SM1291
CHECKING THE SHIFT FORKS
1. Check:
• Shift fork cam follower “1”
• Shift fork pawl “2”
Bends/damage/scoring/wear  Replace the
shift fork.
2. Check:
• Shift fork guide bar
Roll the shift fork guide bar on a flat surface.
Bends  Replace.
EWA12840
WARNING
Do not attempt to straighten a bent shift fork
guide bar.
3. Check:
• Shift fork movement
(along the shift fork guide bar)
Rough movement  Replace the shift forks
and shift fork guide bar as a set.
EAS1SM1292
1
4
62
5
3
8
7
9

TRANSMISSION
5-73
6. Install:
• Shift fork 1 (L) “1”
• Shift fork 2 (C) “2”
• Shift fork 3 (R) “3”
• Shift cam “4”
(to the main axle and the drive axle)
TIP
• Apply molybdenum disulfide oil to the shift
fork grooves.
• Apply engine oil to the shift cam groove and
the bearing contact surface.
• Mesh the shift fork 1 (L) with the 4th wheel
gear “5” and 3 (R) with the 5th wheel gear “7”
on the drive axle.
• Mesh the shift fork 2 (C) with the 3rd pinion
gear “6” on the main axle.7. Install:
• Long shift fork guide bar “1”
• Short shift fork guide bar “2”
• Spring “3”
TIP
• Screw the spring into the shift fork guide bar
lightly beforehand.
• Apply the engine oil on the shift fork guide
bars.
8. Check:
• Operation of shift cam and shift fork
• Transmission operation
Unsmooth operation  Repair.
3
12
6
24
5
3
7
1
M
M
E
2 13
E