Yamaha YZ450FP 2023, Owner'S Service Manual

Page: 221 / 388

VALVES AND VALVE SPRINGS
5-25
EAM30091
CHECKING THE VALVES AND VALVE
GUIDES
1. Measure:
• Valve-stem-to-valve-guide clearance
Out of specification

Replace the valve
guide.
2. Replace:
• Valve guide
TIP
To ease valve guide removal and installation,
and to maintain the correct fit, heat the cylinder
head to 100 °C (212 °F) in an oven.
a. Remove the valve guide with the valve
guide remover “1”.
b. Install the new valve guide with the valve
guide installer “1” and the valve guide re-
mover “2”.
c. After installing the valve guide, expand the
hole in the valve guide with the valve guide
reamer “3” to obtain the proper valve-
stem-to-valve-guide clearance.
TIP
After replacing the valve guide, reface the valve
seat.
Valve-stem-to-valve-guide clearance =
Valve guide inside diameter “a” -
Valve stem diameter “b”
Valve-stem-to-valve-guide clear-
ance limit (intake)
0.080 mm (0.0032 in)
Valve-stem-to-valve-guide clear-
ance limit (exhaust)
0.100 mm (0.0039 in)
1
2
4
5
3
Valve guide installation height “a”
Intake
13.5–13.9 mm (0.53–0.55 in)
Exhaust
12.2–12.6 mm (0.48–0.50 in)
1
2 2 2
1 1