Yamaha YFM250RX 2008 Service Manual page 140

VALVES AND VALVE SPRINGS
2. Replace:
• Valve guide
NOTE: NOTE:
To ease valve guide removal and installation,
and to maintain the correct fit, heat the cylinder
head to 100°C (212°F) in an oven.
a. Remove the valve guide with the valve
guide remover
b. Install the new valve guide with the valve
guide installer
.
c. After installing the valve guide, bore the
valve guide with the valve guide reamer
to obtain the proper valve-stem-to-valve-
guide clearance.
NOTE: NOTE:
After replacing the valve guide, reface the
valve seat.
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.
4-24
ENG
.
and valve guide remover
Valve guide remover (ø6)
90890-04064
Valve guide remover (6.0 mm)
YM-04064-A
Valve guide installer (ø6)
90890-04065
Valve guide installer (6.0 mm)
YM-04065-A
Valve guide reamer (ø6)
90890-04066
Valve guide reamer (6.0 mm)
YM-04066