2014 YAMAHA YZ250F Owners Manual

ENGINE REMOVAL
5-8
3. Replace:
• Fiber “1”
4. Install:
• Silencer body “1”
•Bolt “2”
TIP
Apply heat-resistant sealant to the areas “a”
shown, making sure that there are no gaps in
the beads of sealant.
5. Replace:
• Fiber “1”
TIP
Stuff the fiber into the silencer body by using a
flat board “2”.
6. Install:
• Silencer cap “1”
•Rivet “2”
TIP
• Apply heat-resistant sealant to the areas “a”
shown, making sure that there are no gaps in
the beads of sealant.
• Take care not to allow the fiber out of place
when installing the silencer body “3”.
EAS1SM1203INSTALLING THE ENGINE
1. Install:
• Engine “1”
Install the engine from the right side.
• Pivot shaft “2”
• Engine mounting bolt (lower side) “3”
• Front engine bracket “4”
• Engine bracket bolt (front side) “5”
• Engine mounting bolt (front side) “6”
• Upper engine bracket “7”
• Engine bracket bolt (upper side) “8”
• Engine mounting bolt (upper side) “9”
TIP
Apply molybdenum disulfide grease to the pivot
shaft. Silencer body bolt
8 Nm (0.8 m·kgf, 5.8 ft·lbf)
LOCTITE®
1
T R..
a
12LT
2
1
Pivot shaft
85 Nm (8.5 m·kgf, 61 ft·lbf)
Engine mounting bolt (lower side)
53 Nm (5.3 m·kgf, 38 ft·lbf)
Engine bracket bolt (front side)
34 Nm (3.4 m·kgf, 25 ft·lbf)
Engine mounting bolt (front side)
55 Nm (5.5 m·kgf, 40 ft·lbf)
Engine bracket bolt (upper side)
34 Nm (3.4 m·kgf, 25 ft·lbf)
Engine mounting bolt (upper
side)
45 Nm (4.5 m·kgf, 33 ft·lbf)
1
1 a233
T R..
T R..
T R..
T R..
T R..
T R..

ENGINE REMOVAL
5-9
EAS1SM1204INSTALLING THE BRAKE PEDAL
1. Install:
• Spring “1”
• Brake pedal “2”
• O-rings “3”
• Bolt (brake pedal) “4”
•Clip “5”
TIP
Apply the lithium soap base grease on the bolt,
O-rings and brake pedal bracket.
EAS1SM1205INSTALLING THE DRIVE SPROCKET
1. Install:
• Drive sprocket “1”
• Drive chain “2”
TIP
Install the drive sprocket together with the drive
chain.2. Install:
• Lock washer “1”
• Nut (drive sprocket) “2”
TIP
Tighten the nut while applying the rear brake.
ECA33DD040
NOTICE
Make sure to tighten to specification; other-
wise, it may damage the other part that is
fastened together.
3. Bend the lock washer tab to lock the nut.
4. Install:
• Drive sprocket guide
• Drive sprocket cover “1”
• Bolt (drive sprocket cover) “2” Bolt (brake pedal)
26 Nm (2.6 m·kgf, 19 ft·lbf)
M
78
9
9 8
7
4 1
2
43
5
56
New
T R..
1 2
3
45
LS
Nut (drive sprocket)
75 Nm (7.5 m·kgf, 54 ft·lbf)
Bolt (drive sprocket cover)
7 Nm (0.7 m·kgf, 5.1 ft·lbf)
New
T R..
T R..
21

ENGINE REMOVAL
5-10
EAS1SM1206INSTALLING THE EXHAUST PIPE AND
MUFFLER
1. Install:
•Gasket
• Exhaust pipe 1 “1”
• Nut (exhaust pipe 1) “2”
TIP
First temporarily tighten nuts to 13 Nm (1.3
m·kgf, 9.4 ft·lbf). Then retighten them to 20 Nm
(2.0 m·kgf, 14 ft·lbf).
2. Install:
•Clamp
• Exhaust pipe 2 “1”
• Bolt (exhaust pipe 2) “2”
TIP
Install and temporarily tighten the exhaust pipe
2 with its end positioned as shown with respect
to the exhaust pipe 1.3. Install:
•Clamp
• Silencer “1”
• Bolt (silencer) “2”
TIP
Install and temporarily tighten the silencer so
that its joint is positioned as shown with respect
to the exhaust pipe 2.
4. Tighten:
• Bolt (exhaust pipe 2)
•Clamp
TIP
Tighten while checking that their front and rear
joints are inserted in position. Nut (exhaust pipe)
20 Nm (2.0 m·kgf, 14 ft·lbf)
New
T R..
1
22
1
2
2mm (0.08in)
Bolt (silencer)
30 Nm (3.0 m·kgf, 22 ft·lbf)
Bolt (exhaust pipe 2)
20 Nm (2.0 m·kgf, 14 ft·lbf)
Clamp
12 Nm (1.2 m·kgf, 8.7 ft·lbf)
T R..
2
2
1
2mm (0.08in)
T R..
T R..

CAMSHAFT
5-11
EAS1SM1207
CAMSHAFT
Removing the cylinder head cover
Order Part name Q’ty Remarks
Seat Refer to “GENERAL CHASSIS” on page 4-1.
Side cover (left/right) Refer to “GENERAL CHASSIS” on page 4-1.
Air scoop (left / right) Refer to “GENERAL CHASSIS” on page 4-1.
Fuel tank Refer to “FUEL TANK” on page 7-1.
1 Spark plug 1
2 Cylinder head breather hose 1
3 Bolt (cylinder head cover) 3
4 Cylinder head cover 1
5 Cylinder head cover gasket 1
6 Timing chain guide (top side) 1
7 Cylinder head cover gasket 1
For installation, reverse the removal proce-
dure.
1
4
6 7
5 2
3
10 Nm (1.0 mkgf, 7.2 ftIbf)T.R
.
13 Nm (1.3 mkgf, 9.4 ftIbf)T.R.
3

CAMSHAFT
5-12
Removing the camshaft
Order Part name Q’ty Remarks
1Timing mark accessing screw
1
2Crankshaft end accessing screw
1
3Timing chain tensioner cap bolt
1
4Timing chain tensioner
1
5Gasket
1
6Camshaft cap bolt
8
7Camshaft cap
2
8Clip
2
9Exhaust camshaft
1
10Intake camshaft
1
For installation, reverse the removal proce-
dure.
6 Nm (0.6 mkgf, 4.3 ftIbf)T.R.
6 Nm (0.6 mkgf, 4.3 ftIbf)T.R.
10 Nm (1.0 mkgf, 7.2 ftIbf)T.R.
10 Nm (1.0 mkgf, 7.2 ftIbf)T.R.
10 Nm (1.0 mkgf, 7.2 ftIbf)T.R.10 Nm (1.0 mkgf, 7.2 ftIbf)T.R.
5
8
3
4
1
2
7
6
5 (4)(4)
6
M
M
E
New
New
New
E
E

CAMSHAFT
5-13
EAS1SM1208REMOVING THE CAMSHAFT
1. Remove:
• Timing mark accessing screw “1”
• Crankshaft end accessing screw “2”
2. Align:
• Alignment mark
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Turn the crankshaft counterclockwise with a
wrench.
b. Align the top dead center (TDC) mark “a” on
the rotor with the alignment mark “b” on the
crankcase cover.
TIP
Align the alignment mark “c” on the exhaust
camshaft sprocket and the alignment mark “d”
on the intake camshaft sprocket with the edge
of the cylinder head.
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3. Remove:
• Timing chain tensioner cap bolt “1”
• Timing chain tensioner “2”
•Gaskets4. Remove:
• Bolt (camshaft cap) “1”
• Camshaft cap “2”
• Clip “3”
TIP
• Remove the bolts (camshaft cap) in a criss-
cross pattern, working from the outside in.
• In order to prevent the clip from falling into the
crankcase, remove the camshaft cap.
ECA33DD027
NOTICE
The bolts (camshaft cap) must be removed
evenly to prevent damage to the cylinder
head, camshafts or camshaft caps.
5. Remove:
• Exhaust camshaft “1”
• Intake camshaft “2”
TIP
Attach a wire “3” to the timing chain to prevent
it from falling into the crankcase.
1
2
b
a
dc
1 2
1
2
3

CAMSHAFT
5-14
EAS1SM1209CHECKING THE CAMSHAFT
1. Check:
• Camshaft lobes
Blue discoloration/pitting/scratches  Re-
place the camshaft.
2. Measure:
• Camshaft lobe dimensions “A” and “B”
Out of specification  Replace the cam-
shaft.3. Measure:
• Camshaft runout
Out of specification  Replace.
4. Measure:
• Camshaft-journal-to-camshaft-cap clear-
ance
Out of specification  Measure the cam-
shaft journal diameter.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Install the camshaft into the cylinder head.
b. Position a strip of Plastigauge® “1” onto the
camshaft journal as shown. Camshaft lobe dimensions
Intake A
31.730–31.830 mm (1.2492–
1.2531 in)
Limit
31.630 mm (1.2453 in)
Intake B
22.450–22.550 mm (0.8839–
0.8878 in)
Limit
22.350 mm (0.8799 in)
Exhaust A
33.370–33.470 mm (1.3138–
1.3177 in)
Limit
33.270 mm (1.3098 in)
Exhaust B
25.211–25.311 mm (0.9926–
0.9965 in)
Limit
25.111 mm (0.9886 in)
1
2
3
Camshaft runout limit
0.030 mm (0.0012 in)
Camshaft-journal-to-camshaft-
cap clearance
0.028–0.062 mm (0.0011–0.0024
in)
1

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.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
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.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
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