Checking The Valve Seats - Yamaha YFM250RX 2008 Service Manual

VALVES AND VALVE SPRINGS
5. Measure:
• Valve margin thickness D
Out of specification → Replace the valve.
6. Measure:
• Valve stem runout
Out of specification → Replace the valve.
NOTE: NOTE:
• When installing a new valve, always replace
the valve guide.
• If the valve is removed or replaced, always
replace the oil seal.

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.
4-25
ENG
Valve margin thickness
Valve margin thickness D (intake)
0.80 ~ 1.20 mm
(0.0315 ~ 0.0472 in)
Valve margin thickness D
(exhaust)
0.80 ~ 1.20 mm
(0.0315 ~ 0.0472 in)
Valve stem runout
0.01 mm (0.0004 in)