Yamaha 20C, Owner'S Manual

Page: 138 / 203

4-11
Before fitting the spark plug, measure the
electrode gap with a wire thickness
gauge; adjust the gap to specification if
necessary.
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.
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.
1
Spark plug gap
2
Spark plug I.D. mark (NGK)
GB
Spark plug gap:
Refer to “SPECIFICATIONS”, page 4-1.
Initial of spark plug
Plug wrench size
I.D. mark
B 21 mm (13/16 in.)
C/BK 16 mm (5/8 in.)
D 18.3 mm (23/32 in.)
903022
q
w
Spark plug torque:
Refer to “SPECIFICATIONS”, page 4-1.
61R-9-73-4A (GB,F,ES) 5/12/00 9:27 AM Page 32