Checking The Valve Seats - Yamaha RAPTOR YFM125RA Service Manual

Valve guide remover (ø5)
90890-04097
Valve guide remover (5.0 mm)
YM-04097
Valve guide installer (ø5)
90890-04098
Valve guide installer (5.0 mm)
YM-04098
Valve guide reamer (ø5)
90890-04099
Valve guide reamer (5.0 mm)
YM-04099
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
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)
0.40–0.80 mm (0.0157–0.0315
in)
Valve margin
(exhaust)
0.80–1.20 mm (0.0315–0.0472
in)
6. Measure:
• Valve stem runout
Out of specification → Replace the valve.
VALVES AND VALVE SPRINGS
TIP
• When installing a new valve, always replace
the valve guide.
• If the valve is removed or replaced, always
replace the oil 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:
thickness
• Valve seat width "a"
Out of specification → Replace the cylin-
der head.
5-21
Valve stem runout
Valve stem runout
0.010 mm (0.0004 in)
Valve seat width
Valve seat width (intake)
0.90–1.10 mm (0.0354–0.0433
in)
Valve seat width (exhaust)
0.90–1.10 mm (0.0354–0.0433
in)