2012 YAMAHA YZ250F seats

3-1
MAINTENANCE INTERVALS
REGULAR INSPECTION AND ADJUSTMENTS
MAINTENANCE INTERVALS
• The following schedule is intended as a general guide to maintenance and lubrication. Bear in mind that such factors as
weather, terrain, geographical location, and individual usage will alter the required maintenance and lubrication intervals.
If you are a doubt as to what intervals to follow in maintaining and lubricating your machine, consult your Yamaha dealer.
• Periodic inspection is essential in making full use of the machine performance. The service life of the parts varies sub-
stantially 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
ENGINE OIL
Replace●●
Inspect●●
OIL FILTER ELEMENT, OIL
STRAINER
Clean●
VALVES
Check the valve clearances●●The engine must be cold.
Inspect●Check the valve seats and valve
stems for wear.
Replace●
VALVE SPRINGS
Inspect●Check the free length and the tilt.
Replace●
VALVE LIFTERS
Inspect●Check for scratches and wear.
Replace●
CAMSHAFTS Inspect the camshaft surface.
Inspect●Inspect the decompression system.
Replace●
TIMING CHAIN SPROCKETS,
TIMING CHAIN
Inspect●Check for wear on the teeth and for
damage.
Replace●
PISTON
Inspect●●Inspect crack.
Clean●Inspect carbon deposits and eliminate
them.
Replace●It is recommended that the piston pin
and ring are also replaced at the same
time.
PISTON RING
Inspect●Check ring end gap.
Replace●●
3

4-22
CYLINDER HEAD
CHECKING THE CYLINDER HEAD
1. Eliminate:
• Carbon deposits (from the com-
bustion chambers)
Use a rounded scraper.
Do not use a sharp instrument to
avoid damaging or scratching:
• Spark plug threads
• Valve seats
2. Inspect:
• Cylinder head
Scratches/damage→Replace.
Replace the titanium valves with the
cylinder head.
Refer to "CHECKING THE
VALVE".
3. Measure:
• Cylinder head warpage
Out of specification→Resurface.
Warpage measurement and resur-
facing steps:
a. Place a straightedge and a feeler
gauge across the cylinder head.
b. Use a feeler gauge to measure
the warpage.
c. If the warpage is out of specifica-
tion, resurface the cylinder head.
d. Place a 400–600 grit wet sandpa-
per on the surface plate, and re-
surface the head using a figure-
eight sanding pattern.
To ensure an even surface rotate the
cylinder head several times.
INSTALLING THE CYLINDER
HEAD
1. Install:
• Dowel pin "1"
• Cylinder head gasket "2"
• Timing chain guide (exhaust side)
"3"
• Cylinder head "4"
While pulling up the timing chain, in-
stall the timing chain guide (exhaust
side) and cylinder head.
2. Install:
• Washer "1"
• Cable guide "2"
• Bolts [L = 145 mm (5.71 in)] "3"
• Bolts [L = 135 mm (5.31 in)] "4"
•Nuts "5"
• Apply the molybdenum disulfide
grease on the thread and contact
surface of the bolts.
• Follow the numerical order shown
in the illustration. Tighten the bolts
and nuts in two stages.
3. Install:
• Copper washer "1"
• Oil delivery pipe "2"
• Union bolt (M8) "3"
• Union bolt (M10) "4"
First tighten the union bolts temporar-
ily. Then retighten them with the width
"a" across flats of the oil delivery pipe
held tight with a spanner.
4. Install:
• Radiator pipe "1"
• Bolt (radiator pipe) "2" Cylinder head warpage:
Less than 0.05 mm
(0.002 in)
Bolts [L = 145 mm (5.71
in)]:
38 Nm (3.8 m•kg, 27
ft•lb)
Bolts [L = 135 mm (5.31
in)]:
38 Nm (3.8 m•kg, 27
ft•lb)
Nuts:
10 Nm (1.0 m•kg, 7.2
ft•lb)
Union bolt (M8):
18 Nm (1.8 m•kg, 13
ft•lb)
Union bolt (M10):
20 Nm (2.0 m•kg, 14
ft•lb)
Bolt (radiator pipe):
10 Nm (1.0 m•kg, 7.2
ft•lb)

4-25
VALVES AND VALVE SPRINGS
3. Inspect:
• Valve face
Pitting/wear→Grind the face.
• Valve stem end
Mushroom shape or diameter
larger than the body of the stem→
Replace.
4. Measure:
• Margin thickness "a"
Out of specification→Replace.
5. Measure:
• Runout (valve stem)
Out of specification→Replace.
• When installing a new valve always
replace the guide.
• If the valve is removed or replaced
always replace the oil seal.
6. Eliminate:
• Carbon deposits
(from the valve face and valve
seat)
7. Inspect:
• Valve seat
Pitting/wear→Reface the valve
seat.
8. Measure:
• Valve seat width "a"
Out of specification→Reface the
valve seat.
Measurement steps:
a. Apply Mechanic's blueing dye
(Dykem) "b" to the valve face.
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 pattern.
d. Measure the valve seat width.
Where the valve seat and valve
face made contact, blueing will
have been removed.
e. If the valve seat is too wide, too
narrow, or the seat is not cen-
tered, the valve seat must be
refaced.
9. Lap:
• Valve face
• Valve seat
This model uses titanium intake
and exhaust valves. Titanium
valves that have been used to lap
the valve seats must not be used.
Always replace lapped valves with
new valves.
• When replacing the cylinder head,
replace the valves without lapping
the valve seats and valve faces.• When replacing the valves or valve
guides, use new valves to lap the
valve seats, and then replace them
with new valves.
Lapping steps:
a. Apply a coarse lapping compound
to the valve face.
Do not let the compound enter the
gap between the valve stem and
the guide.
b. Apply molybdenum disulfide oil to
the valve stem.
c. Install the valve into the cylinder
head.
d. Turn the valve until the valve face
and valve seat are evenly pol-
ished, then clean off all of the
compound.
For best lapping results, lightly tap
the valve seat while rotating the valve
back and forth between your hands.
e. Apply a fine lapping compound to
the valve face and repeat the
above steps.
After every lapping operation be sure
to clean off all of the compound from
the valve face and valve seat.
f. Apply Mechanic's blueing dye
(Dykem) to the valve face.
g. Install the valve into the cylinder
head. Margin thickness:
Intake:
0.8 mm (0.0315 in)
Exhaust:
0.7 mm (0.0276 in)
Runout limit:
0.01 mm (0.0004 in)
Valve seat width:
Intake:
0.9–1.1 mm
(0.0354–0.0433 in)
:1.6 mm
(0.0630 in)
Exhaust:
0.9–1.1 mm
(0.0354–0.0433 in)
:1.6 mm
(0.0630 in)