Yamaha F20A Manuel D'utilisation page 156

w
When fitting the plug, always clean the
gasket surface and use a new gasket.
Wipe off any dirt from the threads and
screw in the spark plug to the correct
torque.
Spark plug torque:
Refer to "SPECIFICATIONS", page 4-1.
NOTE:
If a torque-wrench is not available when
you are fitting a spark plug, a good esti-
mate of the correct torque is 1/4 to 1/2 a
turn past finger-tight. Have the spark plug
adjusted to the correct torque as soon as
possible with a torque-wrench.
q
Initial of spark plug
I.D. mark
903022
B
C/BK
D
1 Spark plug gap
2 Spark plug I.D. mark (NGK)
4-16
GB
Plug wrench size
21 mm (13/16 in.)
16 mm (5/8 in.)
18.3 mm (23/32 in.)