Yamaha Tenere 700 2020, Service Manual

Page: 217 / 472

VALVES AND VALVE SPRINGS
5-30
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 stem runout
Out of specification
→
Replace the valve.
TIP
• When installing a new valve, always replace
the valve guide.
• If the valve is removed or replaced, always re-
place the valve stem seal.
EAS30285
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 blue layout fluid “b” 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
impression.
d. Measure the valve seat width.
TIP
Where the valve seat and valve face contacted
one another, the blueing will have been re-
moved.
4. Lap:
• Valve face
• Valve seat
TIP
After replacing the cylinder head or replacing the
valve and valve guide, the valve seat and valve
face should be lapped.
a. Apply a coarse lapping compound “a” to
the valve face.
NOTICE
ECA13790
Do not let the lapping compound enter the
gap between the valve stem and the valve
guide.
Valve stem runout
0.010 mm (0.0004 in)
Valve seat contact width (intake)
0.90–1.10 mm (0.0354–0.0433 in)
Valve seat contact width (ex-
haust)
0.90–1.10 mm (0.0354–0.0433 in)
G0 88 965
G0 88 966
G0 88 967