Toro Greensmaster Flex 21 Service Manual page 24

NORMAL
Has gray or light tan deposits on the firing
tip.
LEAD FOULED
Has dark black, gray, tan, or yellow depos-
its. May have a fused glazed coating on the
insulator tip.
Caused by highly leaded gasoline.
Replace spark plug.
GAP BRIDGED
Gap between electrodes is closed by de-
posit build up.
May be caused by carbon or oil fouling.
Replace spark plug.
Engine
OVER HEATING
Light gray or white insulator with small gray
brown or black spots. Electrode has a bluish
burnt appearance.
May be caused by engine over heating,
loose spark plug, wrong fuel type, plug heat
range too hot, or incorrect ignition timing.
Replace spark plug.
CARBON FOULED
Black dry fluffy carbon deposits are found
on insulator tip, electrodes, and exposed
shell surfaces.
Weak ignition, plug heat range too cold, fuel
mixture too rich, or excessive idling may be
the cause.
Replace spark plug.
OIL FOULED
Wet black deposits can be found on elec-
trodes, insulator, and in the bore.
Excessive oil entering the combustion
chamber past worn valve guides, valve
stems, rings, piston, and/or cylinder bore.
Replace spark plug.
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FUSED SPOT DEPOSIT
Has spotty or melted deposits resembling
blisters or bubbles.
Caused by sudden acceleration.
Replace spark plug.
WORN
Has severely eroded or worn electrodes.
Caused by normal wear.
Replace spark plug.
PRE–IGNITION
Electrodes are melted and the insulator
may be blistered. Metallic deposits on the
insulator indicate engine damage.
Engine overheating, burnt valves, plug heat
range too hot, incorrect ignition timing or ad-
vance, or wrong type of fuel are causes.
Replace spark plug.
Greensmaster Flex 21