Yamaha YZ 2015 Series, Owner'S Service Manual

Page: 232 / 396

VALVES AND VALVE SPRINGS
5-29
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 width “c” again. If the
valve seat width is out of specification,
reface and lap the valve seat.
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EASB291229
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.
Free length (intake)
36.69 mm (1.44 in)
Limit
35.69 mm (1.41 in)
Free length (exhaust)
34.86 mm (1.37 in)
Limit
33.86 mm (1.33 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)
1.6 mm (0.06 in)
Spring tilt (exhaust)
1.5 mm (0.06 in)