2002 YAMAHA YZ250F Valve clearance

3 - 23
INSP
ADJ
VALVE CLEARANCE INSPECTION AND ADJUSTMENT
Locate the rounded-off value and the
measured valve clearance in the chart
“PAD SELECTION TABLE”. The field
where these two coordinates intersect
shows the new pad number to use.
NOTE:
Use the new pad number only as a guide
when verifying the valve clearance adjust-
ment.
Install the new pads 7 and the valve lift-
ers 8.
NOTE:
Apply the engine oil on the valve lifters.
Apply the molybdenum disulfied oil on the
valve stem ends.
Valve lifter must turn smoothly when
rotated with a finger.
Be careful to reinstall valve lifters and
pads in their original place.
Install the decompression shaft 9, copper
washer 0, bolt (decompression shaft) A,
guide B, bolt (guide) C and decompres-
sion cable D.
NOTE:
Apply the engine oil on the decompression
shaft.
T R..
Bolt (decompression shaft):
7 Nm (0.7 m • kg, 5.1 ft • lb)
Bolt (guide):
10 Nm (1.0 m • kg, 7.2 ft • lb)
Install the camshafts (exhaust and intake).
Refer to “CAMSHAFTS” section in the
CHAPTER 4.

3 - 24
INSP
ADJ
VALVE CLEARANCE INSPECTION AND ADJUSTMENT
INTAKE
MEASURED
CLEARANCEINSTALLED PAD NUMBER
120 125 130 135 140 145 150 155 160 165 170
175 180 185 190 195 200 205 210 215 220 225 230 235 240
0.00 ~ 0.04 120 125 130 135 140 145 150 155
160165 170 175 180 185 190 195 200 205 210 215 220 225 230
0.05 ~ 0.09
120 125 130 135 140 145 150 155 160 165170 175 180 185 190 195 200 205 210 215 220 225 230 235
0.10 ~ 0.15
STANDARD CLEARANCE
0.16 ~ 0.20125130135140145150155160165170175180 185 190 195 200 205 210 215 220 225 230 235240
0.21 ~ 0.25130135140145150155160165170175180185 190 195 200 205 210 215 220 225 230 235240
0.26 ~ 0.30 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
0.31 ~ 0.35 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
0.36 ~ 0.40 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
0.41 ~ 0.45 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
0.46 ~ 0.50 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
0.51 ~ 0.55 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
0.56 ~ 0.60 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
0.61 ~ 0.65 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
0.66 ~ 0.70 175 180 185 190 195 200 205 210 215 220 225 230 235240
0.71 ~ 0.75 180 185 190 195 200 205 210 215 220 225 230 235240
0.76 ~ 0.80 185 190 195 200 205 210 215 220 225 230 235240VALVE CLEARANCE (cold):
0.10 ~ 0.15 mm
Example: Installed is 175
Measured clearance is 0.23 mm
Replace 175 pad with 185 pad
Pad number: (example)
Pad No. 175 = 1.75 mm
Pad No. 185 = 1.85 mm0.81 ~ 0.85 190 195 200 205 210 215 220 225 230 235240
0.86 ~ 0.90 195 200 205 210 215 220 225 230 235240
0.91 ~ 0.95 200 205 210 215 220 225 230 235240
0.96 ~ 1.00 205 210 215 220 225 230 235240
1.01 ~ 1.05 210 215 220 225 230 235240
1.06 ~ 1.10 215 220 225 230 235240
1.11 ~ 1.15 220 225 230 235240
1.16 ~ 1.20 225 230 235240
1.21 ~ 1.25 230 235240
1.26 ~ 1.30 235240
1.31 ~ 1.35 240
EXHAUST
MEASURED
CLEARANCEINSTALLED PAD NUMBER
120 125 130 135 140 145 150 155 160 165 170
175 180 185 190 195 200 205 210 215 220 225 230 235 240
0.00 ~ 0.04 120 125 130 135 140 145 150 155
160 165 170 175 180 185 190 195 200 205 210 215 220 225
0.05 ~ 0.09
120 125 130 135 140 145 150 155 160165 170 175 180 185 190 195 200 205 210 215 220 225 230
0.10 ~ 0.16
120125130135140145150155160165170 175 180 185 190 195 200 205 210 215 220 225230235
0.17 ~ 0.22STANDARD CLEARANCE
0.23 ~ 0.25 125 130 135 140 145 150 155 160 165 170 175
180 185 190 195 200 205 210 215 220 225230235 240
0.26 ~ 0.30130135140145150155160165170175180185 190 195 200 205 210 215 220 225230235240
0.31 ~ 0.35 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.36 ~ 0.40 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.41 ~ 0.45 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.46 ~ 0.50 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.51 ~ 0.55 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.56 ~ 0.60 160 165 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.61 ~ 0.65 165 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.66 ~ 0.70 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.71 ~ 0.75 175 180 185 190 195 200 205 210 215 220 225230235240
0.76 ~ 0.80 180 185 190 195 200 205 210 215 220 225230235240
0.81 ~ 0.85 185 190 195 200 205 210 215 220 225230235240
0.86 ~ 0.90 190 195 200 205 210 215 220 225230235240
VALVE CLEARANCE (cold):
0.17 ~ 0.22 mm
Example: Installed is 175
Measured clearance is 0.27 mm
Replace 175 pad with 185 pad
Pad number: (example)
Pad No. 175 = 1.75 mm
Pad No. 185 = 1.85 mm0.91 ~ 0.95 195 200 205 210 215 220 225230235240
0.96 ~ 1.00 200 205 210 215 220 225230235240
1.01 ~ 1.05 205 210 215 220 225230235240
1.06 ~ 1.10 210 215 220 225230235240
1.11 ~ 1.15 215 220 225230235240
1.16 ~ 1.20 220 225230235240
1.21 ~ 1.25 225230235240
1.26 ~ 1.30 230235240
1.31 ~ 1.35 235240
1.36 ~ 1.40 240

4 - 35
ENGVALVES AND VALVE SPRINGS
INSPECTION
Valve
1. Measure:
Stem-to-guide clearance
Out of specification → Replace the
valve guide. Stem-to-guide clearance =
valve guide inside diameter a –
valve stem diameter b
Clearance (stem to guide):
Intake:
0.010 ~ 0.037 mm
(0.0004 ~ 0.0015 in)
: 0.08 mm (0.003 in)
Exhaust:
0.025 ~ 0.052 mm
(0.0010 ~ 0.0020 in)
: 0.10 mm (0.004 in)
2. Replace:
Valve guide
Replacement steps:
NOTE:
To ease guide removal, installation and to
maintain correct fit heat the cylinder head in
an over to 100 ˚C (212 ˚F).
Remove the valve guide using a valve
guide remover 1.
Install the new valve guide using a valve
guide remover 1 and valve guide installer
2.
After installing the valve guide, bore the
valve guide using a valve guide reamer 3
to obtain proper stem-to-guide clearance.