Checking The Valve Seats - Yamaha 2011 FZ8NA(C) Service Manual

TIP
After replacing the valve guide, reface the
valve seat.
Valve guide remover (ø4)
90890-04111
Valve guide remover (4.0 mm)
YM-04111
Valve guide installer (ø4)
90890-04112
Valve guide installer (4.0 mm)
YM-04112
Valve guide reamer (ø4)
90890-04113
Valve guide reamer (4.0 mm)
YM-04113
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3. Eliminate:
• Carbon deposits
(from the valve face and valve seat)
4. Check:
• Valve face
Pitting/wear → Grind the valve face.
• Valve stem end
Mushroom shape or diameter larger than
the body of the valve stem → Replace the
valve.
5. Measure:
• Valve margin thickness "a"
Out of specification → Replace the valve.
Valve margin thickness
Valve margin thickness (intake)
0.50–0.90 mm (0.0197–0.0354
in)
Valve margin
(exhaust)
0.50–0.90 mm (0.0197–0.0354
in)
VALVES AND VALVE SPRINGS
6. Measure:
• Valve stem runout
Out of specification → Replace the valve.
TIP
• When installing a new valve, always replace
the valve guide.
• If the valve is removed or replaced, always
replace the valve stem seal.
EAS24300

CHECKING THE VALVE SEATS

The following procedure applies to all of the
valves and valve seats.
1. Eliminate:
• Carbon deposits
(from the valve face and valve seat)
2. Check:
• Valve seat
Pitting/wear → Replace the cylinder
head.
3. Measure:
• Valve seat width "a"
Out of specification → Replace the cylin-
thickness
der head.
5-27
Valve stem runout
0.010 mm (0.0004 in)