Yamaha MTN850-A 2017, Service Manual, Page: 117 / 560

PERIODIC MAINTENANCE
3-7
d. To measure the valve clearances of the other
cylinders, starting with cylinder #1 at TDC,
turn the crankshaft counterclockwise as
specified in the following table.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
5. Remove:
• Camshaft
TIP
•
Refer to “CAMSHAFTS” on page 5-9.
•
When removing the timing chain and cam-
shafts, fasten the timing chain with a wire to re-
trieve it if it falls into the crankcase.
6. Adjust:
• Valve clearance
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Remove the valve lifter “1” and the valve pad
“2” with a valve lapper “3”.
TIP
• Cover the timing chain opening with a rag to
prevent the valve pad from falling into the
crankcase.
• Make a note of the position of each valve lifter
“1” and valve pad “2” so that they can be in-
stalled in the correct place.
b. Calculate the difference between the speci-
fied valve clearance and the measured valve
clearance.
Example:
Specified valve clearance = 0.11–0.20 mm
(0.004–0.008 in)
Measured valve clearance = 0.25 mm (0.010
in)
0.25 mm (0.010 in) - 0.20 mm (0.008 in) =
0.05 mm (0.002 in)
c. Check the thickness of the current valve pad.
TIP
The thickness “a” of each valve pad is marked in
hundredths of millimeters on the side that touch-
es the valve lifter.
Example:
If the valve pad is marked “158”, the pad
thickness is 1.58 mm (0.062 in).
d. Calculate the sum of the values obtained in
steps (b) and (c) to determine the required
valve pad thickness and the valve pad num-
ber.
Example:
1.58 mm (0.062 in) + 0.05 mm (0.002 in) =
1.63 mm (0.064 in)
The valve pad number is 163.
e. Round off the valve pad number according to
B. Degrees that the crankshaft is turned coun-
terclockwise
C. Cylinder
D. Combustion cycle
Cylinder #2 240

Cylinder #3 480

Valve lapper
90890-04101
Valve lapping tool
YM-A8998
B
C
D
D
D
1 2