Yamaha YFM660RN Service Manual page 65

ADJUSTING THE VALVE CLEARANCE
6.Check:
Valve clearance
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:
Turn the crankshaft counterclockwise with a
wrench.
Align the "I" mark 1 on the rotor with the sta-
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
(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
counterclockwise one turn.
Measure the valve clearance using a feeler
gauge 3.
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