Yamaha RD400 Betriebsanleitung Seite 85

Spark plug inspection
The spark plug is an important engine com-
ponent and is easy t o inspect. The c o n d i t i o n
of the spark plug can indicate something of
the c o n d i t i o n of the engine. Check the colora-
t i o n on the white porcelain insulator around
the center electrode. The ideal coloration at
this p o i n t is a medium t o light tan color for a
machine that is being ridden normally. If a
spark plug shows a distinctly different color,
there could be something wrong w i t h the
engine. For example, a very w h i t e center
electrode procelain color could indicate and
intake tract air leak or carburetion problem
f o r t h a t cylinder. Do n o t a t t e m p t t o diagnose
such problems yourself. Instead, take the
machine to y o u r Yamaha dealer.
Y o u should periodically remove and inspect
the spark plug because heat and deposits will
cause any spark plug to slowly break d o w n
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