Yamaha XT660 2004, Service Manual

Page: 267 / 463

5 - 27
ENG
VALVES AND VALVE SPRINGS
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 valve stem seal.
EAS00240
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:
• valve seat width
a
Out of specification
→
Replace the cylinder
head.
▼▼▼ ▼ ▼ ▼▼▼ ▼ ▼ ▼▼▼ ▼ ▼ ▼▼▼ ▼ ▼ ▼▼▼ ▼ ▼ ▼▼▼ ▼ ▼▼▼
a. Apply Mechanic’s blueing dye (Dykem) onto
the valve face.
b. Install the valve into the cylinder head.
c. Press the valve through the valve guide and
onto the valve seat to make a clear impres-
sion.
d. Measure the valve seat width.
NOTE:
_
Where the valve seat and valve face contacted
one another, the blueing will have been
removed.
▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲▲▲
Valve stem runout
0.010 mm (0.0004 in)
Valve seat width
Intake
1.00 ~ 1.20 mm
(0.0394 ~ 0.0472 in)
Exhaust
1.00 ~ 1.20 mm
(0.0394 ~ 0.0472 in)