Yamaha YZ450F(S) Owner's Service Manual page 306

VALVES AND VALVE SPRINGS
REMOVAL POINTS
Valve lifter and valve cotter
1. Remove:
NOTE:
Identify each lifter 1 and pad 2 position very
carefully so that they can be reinstalled in their
original place.
2. Check:
Checking steps:
G
G
3. Remove:
NOTE:
Attach a valve spring compressor 1 between
the valve spring retainer and the cylinder head
to remove the valve cotters.
4 - 34
Valve lifters 1
G
Pads 2
G
Valve sealing
G
Leakage at the valve seat → Inspect
the valve face, valve seat and valve
seat width.
Pour a clean solvent 1 into the intake and
exhaust ports.
Check that the valve seals properly.
There should be no leakage at the valve
seat 2.
Valve cotters
G
Valve spring compressor:
YM-4019/90890-04019
ENG