Yamaha YFM660FS Grizzly 4x4 Supplementary Service Manual page 161

ADJUSTING THE VALVE CLEARANCE
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6.Remove:
Timing plug 1
G
7.Check:
Valve clearance
G
Out of specification → Adjust.
Valve clearance (cold):
Intake:
0.10 ~ 0.15 mm
(0.0039 ~ 0.0059 in)
Exhaust:
0.15 ~ 0.20 mm
(0.0059 ~ 0.0079 in)
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Checking steps:
G
Turn the crankshaft counterclockwise with a
wrench.
Align the "I" mark 1 on the rotor with the sta-
G
tionary pointer 2 on the crankcase cover.
When the "I" mark is aligned with the station-
ary pointer, the piston is at the Top Dead
Center (T.D.C.).
NOTE:
When the piston is at the Top Dead Center
G
(T.D.C.) on the compression stroke, there
should be clearance between the valve stem
tips and their respective rocker arm adjusting
screws.
If there is no clearance, rotate the crankshaft
G
counterclockwise one turn.
G
Measure the valve clearance using a feeler
gauge 3.
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CHK
ADJ