Checking The Valve Springs; Checking The Valve Lifters; Installing The Valves - Yamaha MT-09 2021 Service Manual

d. Turn the valve until the valve face and valve
seat are evenly polished, then clean off all
of the lapping compound.
TIP
For the best lapping results, lightly tap the valve
seat while rotating the valve back and forth be-
tween your hands.
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e. Apply a fine lapping compound to the valve
face and repeat the above steps.
f. After every lapping procedure, be sure to
clean off all of the lapping compound from
the valve face and valve seat.
g. Apply blue layout fluid "b" onto the valve
face.
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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 width is out of spec-
ification, reface and lap the valve seat.
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VALVES AND VALVE SPRINGS
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CHECKING THE VALVE SPRINGS

The following procedure applies to all of the
valve springs.
1. Measure:
• Valve spring free length "a"
Out of specification → Replace the valve
spring.
Free length limit (intake)
37.34 mm (1.47 in)
Free length limit (exhaust)
35.89 mm (1.41 in)
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CHECKING THE VALVE LIFTERS

The following procedure applies to all of the
valve lifters.
1. Check:
• Valve lifter
Damage/scratches → Replace the valve lift-
ers and cylinder head.
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INSTALLING THE VALVES

The following procedure applies to all of the
valves and related components.
1. Deburr:
• Valve stem end
(with an oil stone)
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2. Lubricate:
• Valve stem
• Valve stem seal
(with the recommended lubricant)
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