Checking The Valve Springs - Yamaha MBK XMAX 2014 Service Manual

ECA13790
NOTICE
Do not let the lapping compound enter the
gap between the valve stem and the valve
guide.
b. Apply molybdenum disulfide oil onto the
valve stem.
c. Install the valve into the cylinder head.
d. Turn the valve until the valve face and valve
seat are evenly polished, and then clean off
all of the lapping compound.
TIP
For the best lapping results, lightly tap the valve
seat while rotating the valve back and forth be-
tween your hands.
e. Apply a fine lapping compound to the valve
face and repeat the above steps.
f. After every lapping procedure, be sure to
clean off all of the lapping compound from the
valve face and valve seat.
g. Apply blue layout fluid "b" onto the valve face.
h. Install the valve into the cylinder head.
VALVES AND VALVE SPRINGS
i. Press the valve through the valve guide and
onto the valve seat to make a clear impres-
sion.
j. Measure the valve seat contact width again.
If the valve seat contact width is out of speci-
fication, reface and lap the valve seat.
▲ ▲▲▲ ▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲
EAS2DM1043

CHECKING THE VALVE SPRINGS

The following procedure applies to all of the
valve springs.
1. Measure:
• Valve spring free length "a"
Out of specification → Replace the valve
spring.
Free length (intake)
41.71 mm (1.64 in)
Limit
39.62 mm (1.56 in)
Free length (exhaust)
41.71 mm (1.64 in)
Limit
39.62 mm (1.56 in)
2. Measure:
• Compressed valve spring force "a"
Out of specification → Replace the valve
spring.
Installed compression spring
force (intake)
140.00–162.00 N (14.28–16.52
kgf, 31.47–36.42 lbf)
Installed compression spring
force (exhaust)
140.00–162.00 N (14.28–16.52
kgf, 31.47–36.42 lbf)
Installed length (intake)
35.30 mm (1.39 in)
Installed length (exhaust)
35.30 mm (1.39 in)
5-22
▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲▲▲