Spark Plug Condition
The carbon on the electrodes conducts electricity,
and can short the center electrode to ground by either
ceramic insulator or bridging across the gap.
Such a short will prevent an effective
build-up on the plug can also cause other
can heat up red-hot and cause preignition and knock-
which may eventually burn a hole in the top of the
To inspect the spark plugs:
Remove each plug and inspect the ceramic insulator.
Whether or not the right temperature plug is being used
by noting the condition of the ceram-
ic insulator around the
A light brown color
indicates the correct plug is being used
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certain the replacement plugs have the same thread pitch
and reach (length of threaded portion) as the standard
Spark Plug Threads
builds up here
If the plug reach is too short, carbon will build up on
the plug hole threads in the cylinder head, causing over-
heating and making it very difficult to insert the correct
spark plug later.
If the reach is too long, carbon will build up on the
exposed spark plug threads causing overheating, preig-
nition, and possibly burning a hole in the piston top.
In addition, it may be impossible to remove the plug
without damaging the cylinder head.