Yamaha YZ450FP 2023, Owner'S Service Manual

Page: 220 / 388

VALVES AND VALVE SPRINGS
5-24
EAM30090
REMOVING THE VALVES
TIP
Before removing the internal parts of the cylinder
head (e.g., valves, valve springs, valve seats),
make sure that the valves are properly sealed.
1. Remove:
• Valve lifter “1”
•
Adjusting pad “2”
TIP
• Place a cloth in the timing chain space to pre-
vent adjusting pads from falling into the crank-
case.
•
Make a note of the positions of valve lifters and
adjusting pads so that they can be reinstalled
in their original places.
2. Check:
• Valve sealing
Leakage at the valve seat

Check the valve
face, the valve seat, and the valve seat con-
tact width.
Refer to “CHECKING THE VALVE SEATS”
on page 5-26.
a. Pour a clean solvent “a” into the intake and
exhaust ports.
b. Check that the valves are properly sealed.
TIP
Check that there are no kerosene leaks from the
valve seat “1”.
3. Remove:
• Valve cotter “1”
TIP
Remove the valve cotters by compressing the
valve spring with the valve spring compressor
“2” and the valve spring compressor attachment
“3”.
4. Remove:
•
Valve spring retainer “1”
• Valve spring “2”
•
Valve “3”
• Valve stem seal “4”
•
Valve spring seat “5”
TIP
Identify the position of each part very carefully so
that it can be reinstalled in its original place.
Valve lapper (ø14)
90890-04101
Valve lapper (ø14)
YM-A8998
1
2
Valve spring compressor
90890-04200
Valve spring compressor
YM-04019
Valve spring compressor attach-
ment
90890-04108
Valve spring compressor adapter
22 mm
YM-04108
a
1
a
2 2 2
1 1
3 3