Yamaha XN125 2000, Service Manual

Page: 113 / 259

ENG
4-17
c. After installing the valve guide, bore the valve
guide with the valve guide reamer to obtain
the proper valve-stem-to-valve-guide clea-
rance.
NOTE:
After replacing the valve guide, reface the valve
seat .
Valve guide remover (4.5 mm)
90890-04116
Valve guide installer (4.5 mm)
90890-04117
Valve guide reamer (4.5 mm)
90890-04118
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3. Remove:
• 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.
6. Measure:
• valve stem runout
Out of specification
→
Replace the valve.
NOTE:
• When installing a new valve, always replace
the valve guide.
• If the valve is removed or replaced, always
replace the oil seal.
Valve stem runout
0.01 mm
EAS00240
CHECKING THE VALVE SEATS
The following procedure applies to all of the
valves and valve seats.
1. Remove:
• carbon deposits
(from the valve face and valve seat)
2. Check:
• valve seat
Pitting/wear
→
Replace the cylinder head.
VALVES AND VALVE SPRINGS
a