Checking The Valve Springs; Checking The Valve Lifters; Installing The Valves - Yamaha YZ450FX 2019 Owner's Service Manual

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 contact width "c"
again. If the valve seat contact width is out of
specification, reface and lap the valve seat.
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EAM30093

CHECKING THE VALVE SPRINGS

1. Measure:
• Valve spring free length "a"
Out of specification  Replace the valve
spring.
Free length (intake)
40.57 mm (1.60 in)
Limit
38.54 mm (1.52 in)
Free length (exhaust)
37.42 mm (1.47 in)
Limit
35.55 mm (1.40 in)
EAM30094

CHECKING THE VALVE LIFTERS

1. Check:
• Valve lifter
Damage/scratches  Replace the valve lift-
ers and cylinder head.
VALVES AND VALVE SPRINGS
EAM30095

INSTALLING THE VALVES

1. Clean:
• Valve stem end
2. Lubricate:
• Valve stem "1"
• Valve stem seal "2"
Recommended lubricant
Molybdenum disulfide oil
3. Install:
• Spring seat "1"
• Valve stem seal "2"
• Valve "3"
• Valve spring "4"
• Valve spring retainer "5"
(to the cylinder head)
TIP
• Make sure each valve is installed in its original
place.
• Install the valve springs with the larger pitch "a"
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