seats YAMAHA YZ250F 2008 Owners Manual

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.
Item After
break- in Every
race
Every
third
(or 500 km) Every
fifth (or 1,000 km)
As re-
quired Remarks
ENGINE OIL Replace
●●
Inspect●●
OIL FILTER ELEMENT, OIL
STRAINERClean
●
VALVESCheck 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
●
PISTON RING Inspect
●Check ring end gap.
Replace
●●
PISTON PIN Inspect
●
Replace●
CYLINDER HEAD Inspect carbon deposits and eliminate
them.
Inspect and clean
●Change gasket.
3

4-20
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 headScratches/damage
→Replace.
3. Measure: • Cylinder head warpageOut 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"
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)