Spark Plug Inspection - Yamaha BANSHEE YFZ350M 1999 Owner's Manual

EBU00287

Spark plug inspection

The spark plugs are important engine com-
ponents and are easy to inspect. The con-
dition of the spark plugs can indicate the
condition of the engine.
Normally, all spark plugs from the same
engine should have the same color on the
white porcelain insulator around the center
electrode. The ideal color at this point is a
medium to light tan color for a machine that
is being ridden normally. If one spark plug
shows a distinctly different color, there
could be something wrong with the engine.
Do not attempt to diagnose such problems
yourself. Instead, take the machine to a
Yamaha dealer. You should periodically
remove and inspect the spark plugs because
heat and deposits will cause any spark plug to
slowly break down and erode. If electrode ero-
sion becomes excessive, or if carbon and
other deposits are excessive, you should
replace the spark plug with the specified plug.
Standard spark plug:
B8ES (NGK) or
W24ES (DENSO)
Before installing a spark plug, measure the
electrode gap with a feeler gauge and
adjust to specification.
Spark plug gap:
0.7 ~ 0.8 mm (0.028 ~ 0.031 in)
a
a. Spark plug gap
8-11