2014 YAMAHA YZ250F seats

LUBRICATION POINTS AND LUBRICANT TYPES
2-19
EAS1SM1059
LUBRICATION POINTS AND LUBRICANT TYPES
EAS1SM1060ENGINE
Lubrication point Lubricant types
Oil seal lips
Bearing
O-ring
Cylinder head bolt threads, seats, washers
Valve stems
Valve stem ends
Valve lifter outer surface
Camshaft lobe and journal
Valve lifter top surface
Crankshaft journal
Crankshaft big end thrust surfaces
Piston outer surface
Piston pin outer surface
Balancer shaft journal (left)
Decompression system moving parts
Water pump impeller shaft
Oil pump rotors (inner and outer)
Oil passage gasket
Oil pump shaft
Kick gear and ratchet wheel
Kick shaft
Kick idle gear inner surface
Ratchet wheel and ratchet wheel guide contacting portion
Primary drive gear nut threads and contacting surface
Primary driven gear inner surface and end surface
Clutch push rod washer
Clutch push rod 1 outer surface
Clutch push rod 1 thrust surface
Clutch push rod 2 outer surface
Push lever shaft outer surface
Transmission gear inner surface (wheel and pinion) and collar
Transmission gears (shift fork groove)
Shift cam grooves
Shift fork and shift fork guide outer surface
Shift shaft
Shift lever assembly moving parts
LS
E
LS
M
M
M
E
M
E
M
E
E
E
M
E
E
E
LS
E
M
E
E
M
E
E
E
E
E
E
E
M
E
E
E
E
E

MAINTENANCE INTERVALS
3-1
EAS1SM1065
MAINTENANCE INTERVALS
EAS1SM1066MAINTENANCE INTERVALSECA@
NOTICE
• After a break-in or before each race, always check the points shown in “TORQUE-CHECK
POINTS” for tightening torques and retighten them. (“TORQUE-CHECK POINTS” on page 1-
25.)
• Periodic inspection is essential in making full use of the machine performance. The life of
parts varies significantly according to the environment in which the machine runs (e.g., rain,
dirt, etc.). Therefore, earlier inspection is required by reference to the list below.
ITEMAfter
break-
inEvery
race
(about
2.5
hours)Every
third
(about
7.5
hours)Every
fifth
(about
12.5
hours)As re-
quiredRemarks
VALVE
Check the valve
clearancesThe engine must be cold.
Inspect Check the valve seats and the
valve faces for wear.
Replace
VALVE SPRING
Inspect Check the free length and the
tilt.
Replace
VALVE LIFTER
Inspect Check for scratches and wear.
Replace
CAMSHAFT Inspect the camshaft surface.
Inspect Inspect the decompression
system.
Replace
CAMSHAFT
SPROCKET
Inspect Check for wear on the teeth
and for damage.
Replace
PISTON
Inspect Inspect crack.
Clean Inspect carbon deposits and
eliminate them.
Replace Replace the piston, piston pin,
piston pin clip, and piston ring
all as a set.

5
ENGINE
ENGINE REMOVAL......................................................................................... 5-1
REMOVING THE SILENCER ..................................................................... 5-6
REMOVING THE EXHAUST PIPE 2.......................................................... 5-6
REMOVING THE DRIVE SPROCKET ....................................................... 5-6
REMOVING THE ENGINE ......................................................................... 5-7
CHECKING THE SILENCER AND EXHAUST PIPE.................................. 5-7
CHANGING THE SILENCER FIBER ......................................................... 5-7
INSTALLING THE ENGINE........................................................................ 5-8
INSTALLING THE BRAKE PEDAL ............................................................ 5-9
INSTALLING THE DRIVE SPROCKET...................................................... 5-9
INSTALLING THE EXHAUST PIPE AND MUFFLER............................... 5-10
CAMSHAFT.................................................................................................... 5-11
REMOVING THE CAMSHAFT ................................................................. 5-13
CHECKING THE CAMSHAFT.................................................................. 5-14
CHECKING THE TIMING CHAIN AND CAMSHAFT SPROCKET .......... 5-15
CHECKING THE TIMING CHAIN TENSIONERS .................................... 5-15
CHECKING THE DECOMPRESSION SYSTEM...................................... 5-16
INSTALLING THE CAMSHAFTS ............................................................. 5-16
CYLINDER HEAD........................................................................................... 5-18
REMOVING THE CYLINDER HEAD........................................................ 5-20
CHECKING THE TIMING CHAIN GUIDE (INTAKE SIDE) ...................... 5-20
CHECKING THE CYLINDER HEAD ........................................................ 5-20
INSTALLING THE CYLINDER HEAD ...................................................... 5-21
VALVES AND VALVE SPRINGS................................................................... 5-22
REMOVING THE VALVES ....................................................................... 5-23
CHECKING THE VALVES AND VALVE GUIDES ................................... 5-24
CHECKING THE VALVE SEATS ............................................................. 5-25
CHECKING THE VALVE SPRINGS......................................................... 5-27
CHECKING THE VALVE LIFTERS .......................................................... 5-27
INSTALLING THE VALVES ..................................................................... 5-28
CYLINDER AND PISTON............................................................................... 5-30
REMOVING THE PISTON ....................................................................... 5-31
CHECKING THE CYLINDER AND PISTON ............................................ 5-31
CHECKING THE PISTON RINGS............................................................ 5-32
CHECKING THE PISTON PIN ................................................................. 5-33
INSTALLING THE PISTON AND CYLINDER .......................................... 5-33

CYLINDER HEAD
5-20
EAS1SM1215REMOVING THE CYLINDER HEAD
1. Remove:
• Intake camshaft
• Exhaust camshaft
Refer to “REMOVING THE CAMSHAFT” on
page 5-13.
2. Remove:
• Cylinder head nuts
• Cylinder head bolts
TIP
• Loosen the bolts in the proper sequence as
shown.
• Loosen each bolt 1/2 of a turn at a time. After
fully loosening all the bolts, remove them.
EAS1SM1216CHECKING THE TIMING CHAIN GUIDE (IN-
TAKE SIDE)
1. Check:
• Timing chain guide (intake side)
Damage/wear  Replace.
EAS1SM1217CHECKING THE CYLINDER HEAD
1. Eliminate:
• Combustion chamber carbon deposits
TIP
Use a rounded scraper, not a sharp instrument,
in order not to damage or scratch the spark
plug bore threads.2. Check:
• Cylinder head
Damage/scratches  Replace.
TIP
When replacing the cylinder head, replace also
the valve.
“CHECKING THE VALVE SEATS” on page
5-25.
• Cylinder head coolant passages
Mineral deposits/rust  Eliminate.
3. Measure:
• Cylinder head warpage
Out of specification  Resurface the cylin-
der head.
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a. Place a straightedge and a thickness gauge
across the cylinder head.
b. Measure the warpage.
c. If the limit is exceeded, resurface the cylin-
der head as follows.
d. Place a 400–600 grit wet sandpaper on a
surface plate, and resurface the cylinder
head using a figure-eight sanding pattern.
TIP
To ensure an even surface, turn the cylinder
head several times.
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61
2
35
4 x2 x4FWD
Warpage limit
0.05 mm (0.0020 in)

VALVES AND VALVE SPRINGS
5-23
EAS1SM1220REMOVING THE VALVES
TIP
Before removing the internal parts of the cylin-
der head (e.g., valves, valve springs, valve
seats), make sure that the valves are properly
sealed.
1. Remove:
• Valve lifter “1”
• Adjusting pad “2”
TIP
• Place a cloth in the timing chain space to pre-
vent adjusting pads from falling into the crank-
case.
• Make a note of the positions of valve lifters
and adjusting pads so that they can be rein-
stalled in their original places.
2. Check:
• Valve sealing
Leakage at the valve seat  Check the
valve face, the valve seat, and the valve seat
width.
“CHECKING THE VALVE SEATS” on page
5-25.
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a. Pour a clean solvent “a” into the intake and
exhaust ports.b. Check that the valves are properly sealed.
TIP
Check that there are no kerosene leaks from
the valve seat “1”.
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3. Remove:
• Valve cotter “1”
TIP
Remove the valve cotters by compressing the
valve spring with the valve spring compressor
“2” and the valve spring compressor adapter
“3”.
4. Remove:
• Valve spring retainer “1”
• Valve spring “2”
•Valve “3”
• Valve stem seal “4”
• Valve spring seat “5”
TIP
Identify the position of each part very carefully
so that it can be reinstalled in its original place. Valve lapper
90890-04101
Valve lapping tool
YM-A8998
1
2Valve spring compressor
90890-04019
YM-04019
Valve spring compressor adapter
22 mm
90890-04108
YM-04108
a1
a

VALVES AND VALVE SPRINGS
5-25
TIP
After replacing the valve guide, reface the valve
seat.
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3. Eliminate:• Carbon deposits(from the valve face and valve seat)
4. Check: • Valve facePitting/wear  Grind the valve face.
• Valve stem end Mushroom shape or diameter larger than
the body of the valve stem  Replace the
valve.
5. Measure: • Valve margin thickness D “a”Out of specification  Replace the valve. 6. Measure:
• Valve stem runoutOut of specification  Replace the valve.
TIP
• When installing a new valve, always replace
the valve guide.
• If the valve is removed or replaced, always re-
place the oil seal.
EAS1SM1222CHECKING THE VALVE SEATS
1. Eliminate: • Carbon deposits(from the valve face and valve seat)
2. Check:
• Valve seatPitting/wear  Replace the cylinder head.
3. Measure:
• Valve seat width C “a”Out of specification  Replace the cylinder
head.
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a. Apply Mechanic’s blueing dye (Dykem) “b” onto the valve face.
Intake
Valve guide remover (ø5.0)
90890-04097
YM-04097
Valve guide installer (ø5.0) 90890-04098
YM-04098
Valve guide reamer (ø5.0) 90890-04099
YM-04099
Exhaust
Valve guide remover (ø4.5)
90890-04116
YM-04116
Valve guide installer (ø4.5)
90890-04117
YM-04117
Valve guide reamer (ø4.5)
90890-04118
YM-04118
Valve margin thickness D (intake) 1.20 mm (0.0472 in)
Valve margin thickness D (ex-
haust) 0.85 mm (0.0335 in)
Valve stem runout 0.010 mm (0.0004 in)
Valve seat width C (intake) 0.90–1.10 mm (0.0354–0.0433 in)
Valve seat width C (exhaust) 0.90–1.10 mm (0.0354–0.0433 in)

VALVES AND VALVE SPRINGS
5-26
b. Install the valve into the cylinder head.
c. Press the valve through the valve guide and
onto the valve seat to make a clear impres-
sion.
d. Measure the valve seat width “c”.
TIP
Where the valve seat and the valve face are in
contact with each other, the blueing will have
been removed.
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4. Lap:
• Valve face
• Valve seat
ECA1DX1018
NOTICE
This model uses titanium intake and ex-
haust valves.
Do not use the valves used for lapping the
valve seat. Always replace the valves used
for lapping with new ones.
TIP
• When replacing the cylinder head, replace
also the valves with new ones without them.
• When replacing the valves or the valve
guides, use new valves to lap the valve seats,
and then replace them with new valves.
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a. Apply a coarse lapping compound “a” to the
valve face.
ECA13790
NOTICE
Do not let the lapping compound enter the
gap between the valve stem and the valve
guide.
b. Apply molybdenum disulfide oil onto the
valve stem.
c. Install the valve into the cylinder head.
d. Turn the valve until the valve face and the
valve seat are evenly polished, then clean
off all of the lapping compound.
TIP
While turning the valve lapper, tap and lap the
valve seat.
e. Apply a fine lapping compound to the valve
face, and repeat the above steps.
f. After every lapping step, be sure to clean off
all of the lapping compound from the valve
face and the valve seat.
g. Apply Mechanic’s blueing dye (Dykem) “b”
onto the valve face.
h. Install the valve into the cylinder head.
i. Press the valve through the valve guide and
onto the valve seat to make a clear impres-
sion.
j. Measure the valve seat width “c” again. If the
valve seat width is out of specification,
reface and lap the valve seat.
c