Yamaha XV19SX(C), Service Manual

Page: 291 / 494

VALVES AND VALVE SPRINGS
5-42
EAS24280
REMOVING THE VALVES
The following procedure applies to all of the
valves and related components.
NOTE:
Before removing the internal parts of the cylinder
head (e.g., valves, valve springs, valve seats),
make sure the valves properly seal.
1. Check:
• Valve sealing
Leakage at the valve seat
→
Check the valve
face, valve seat, and valve seat width.
Refer to “CHECKING THE VALVE SEATS”
on page 5-44.
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a. Pour a clean solvent “a” into the intake and
exhaust ports.
b. Check that the valves properly seal.
NOTE:
There should be no leakage at the valve seat “1”.
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2. Remove:
• Valve cotters
NOTE:
Remove the valve cotters by compressing the
valve springs with the valve spring compressor
set “1”.
3. Remove:
• Upper spring seat “1”
• Valve spring “2”
• Valve “3”
• Valve stem seal “4”
• Lower spring seat “5”
NOTE:
Identify the position of each part very carefully so
that it can be reinstalled in its original place.
EAS24290
CHECKING THE VALVES AND VALVE
GUIDES
The following procedure applies to all of the
valves and valve guides.
1. Measure:
• Valve-stem-to-valve-guide clearance
Out of specification
→
Replace the valve
guide.
Valve spring compressor
90890-04019
YM-04019
• Valve-stem-to-valve-guide clearance =
Valve guide inside diameter “a” -
Valve stem diameter “b”
Valve-stem-to-valve-guide clear-
ance (intake)
0.010–0.037 mm (0.0004–0.0015
in)
Limit
0.080 mm (0.0032 in)
Valve-stem-to-valve-guide clear-
ance (exhaust)
0.025–0.052 mm (0.0010–0.0020
in)
Limit
0.100 mm (0.0039 in)