Yamaha YZ426F(M)/LC Owner's Service Manual page 178

VALVE CLEARANCE ADJUSTMENT
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4. Remove:
Timing plug 1
Straight plug 2
O-ring
5. Check:
Valve clearance
Out of specification → Adjust.
Valve clearance (cold):
Intake valve:
0.15 ~ 0.20 mm (0.0059 ~ 0.0079 in)
Exhaust valve:
0.25 ~ 0.30 mm (0.0098 ~ 0.0118 in)
Checking steps:
Turn the crankshaft counterclockwise with
a wrench.
NOTE:
Squeezing the decompressor lever allows
the crankshaft to be turned easily.
Align the T.D.C. mark a on the rotor with
the align mark b on the crankcase cover
when piston is at T.D.C. on compression
stroke.
NOTE:
TDC on compression stroke can be found
when the cam lobes are opposite each
other as shown.
Measure the valve clearance using a
feeler gauge 1.
NOTE:
Record the measured reading if the clear-
ance is incorrect.
INSP
ADJ