Yamaha XT660R, Service Manual

Page: 265 / 462

5 - 26
ENG
VALVES AND VALVE SPRINGS
2. Replace:
• valve guide
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
1
.
b. Install the new valve guide with the valve
guide installer 2 and valve guide remover
1
.
c. After installing the valve guide, bore the
valve guide with the valve guide reamer
3
to obtain the proper valve-stem-to-valve-
guide clearance.
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.
Valve guide remover (ø6)
90890-04064
Valve guide installer (ø6)
90890-04065
Valve guide reamer (ø6)
90890-04066
5. Measure:
• valve margin thickness
a
Out of specification
→
Replace the valve.
Valve margin thickness
0.80 ~ 1.20 mm
(0.0315 ~ 0.0472 in)