Yamaha YZ250 Owner's Service Manual page 212

ELECTRICAL/SPARK PLUG INSPECTION
EC370000
ELECTRICAL
EC371001
SPARK PLUG INSPECTION
1. Remove:
9 Spark plug
2. Inspect:
9 Electrode 1
Wear/Damage ¡ Replace.
9 Insulator color 2
Normal condition is a medium to light tan
color.
Distinctly different color ¡ Check the
engine condition.
NOTE:
When the engine runs for many hours at low
speeds, the spark plug insulator will become
sooty, even if the engine and carburetor are in
good operating condition.
3. Measure:
9 Plug gap a
Use a wire gauge or thickness gauge.
Out of specification ¡ Regap.
Spark plug gap:
0.5~0.6 mm (0.020~0.024 in)
Standard spark plug:
BR8EG/NGK (resistance type)
4. Clean the plug with a spark plug cleaner if
necessary.
5. Tighten:
9 Spark plug
NOTE:
9 Before installing a spark plug, clean the
gasket surface and plug surface.
9 Finger-tighten a the spark plug before torquing
to specification b.
3-38
INSP
ADJ
20 Nm (2.0 m•kg, 14 ft•lb)