Yamaha WR250F 2017, Owner'S Service Manual

Page: 258 / 432

VALVES AND VALVE SPRINGS
6-29
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 contact width “c”
again. If the valve seat contact width is out of
specification, reface and lap the valve seat.
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EAS2GBB253 CHECKING THE VALVE SPRINGS
1. Measure:
• Valve spring free length “a”
Out of specification

Replace the valve
spring.
2. Measure:
• Compressed valve spring force “a”
Out of specification

Replace the valve
spring.
3. Measure:
• Valve spring tilt “a”
Out of specification

Replace the valve
spring.
EAS2GBB254 CHECKING THE VALVE LIFTERS
1. Check:
• Valve lifter
Damage/scratches

Replace the valve lift-
ers and cylinder head.
Free length (intake)
36.69 mm (1.44 in)
Limit
34.85 mm (1.37 in)
Free length (exhaust)
34.86 mm (1.37 in)
Limit
33.11 mm (1.30 in)
b. Installed length
Installed compression spring
force (intake)
146.00–168.00 N (14.89–17.13
kgf, 32.82–37.77 lbf)
Installed compression spring
force (exhaust)
137.00–157.00 N (13.97–16.01
kgf, 30.80–35.29 lbf)
Installed length (intake)
31.40 mm (1.24 in)
Installed length (exhaust)
28.50 mm (1.12 in)
Spring tilt (intake)
2.5 °/1.6 mm (2.5 °/0.06 in)
Spring tilt (exhaust)
2.5 °/1.5 mm (2.5 °/0.06 in)