Spark Plug Diagnostics
Heavy Carbon
This plug
has heavy carbon build up. This engine had a blown crank seal on the tranny
side of the crank. Tranny oil entered the crankcase and was burned in the
combustion chamber. Engines like this will billow thick blue smoke out the
exhaust pipe.
This plug
is wet fouled. The spark plug's heat range is either too cold or the carb
jetting is too rich.
This plug
has a shiny appearance. The engine had a problem with air filter sealing.
Sand entered through the filter and into the engine. The high combustion
temperatures caused the sand to melt and form glass around the spark plug.
This plug
has tiny globs of aluminum packed around the insulator. The engine suffered
a meltdown from ignition timing that was advanced too much. The heat could
not transfer from the spark plug fast enough and the center of the piston
melted causing the molten aluminum to collect on the plug.
Perfect
Color
This is
a perfect plug. The color is mocha brown so the carb jetting is optimum.
The first three threads are black signifying the plug's heat range is matched
to the application. There are relatively low deposits considering that this
engine was run on regular pump petrol.