Spark Plug Condition - Polaris 1999 Sportsman 400 Service Manual

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CHAPTER THREE
SPARK PLUG CONDITION
NORMAL
Identified by light tan or
gra y deposits on the
firing ti p.
Can be cleaned.
CARBON FOULED
Identif ied by black, dry fluffy
car bo n deposits on in su lator
ti ps, ex posed she ll surfaces
and electrodes.
Caused by too co ld a plug,
weak Igniti on, di rt y air
cleaner, too rich fuel mixture
o r excessive Idling.
Can be
cleaned.
FUSED SPOT DEPOSIT
Identified by melted or spotty
dep osits resembling bubbles
or blisters .
Caused by sudden
acceleration. Can be clea ned.
GAP BRIDGED
Identified by deposit bui ldup
closing gap between
electrodes.
Caused by all or carbon
fouling. If deposits are not
excessive, the plug can be
LEAD FOULED
Identified by dark gray, black,
yellow or tan deposit s or a fused
glazed coating on the insu lator tip.
Caused by highly leaded
gasoline. Can be cleaned .
OVERHEATING
Identif ied by a white or light
gray
in su lator with small black
or gra y brown spots with
bluish-burnt appe ara nce of
electrodes .
Caused by engine
overheating, wrong type of
fuel, loose spark plugs, too
hot a pl ug or Incorrect ignition
timing . Replace t he plug.
OIL FOULED
Identified by wet black deposits on
the insulator shell bore and
electrodes.
Caused by excessive oil entering
combustion chamber through worn
rings and pistons, excessive
clea rance between valve gu ides and
stems
OJ
worn or loose bearings.
Can be cleaned. If engi ne Is not
repa ired, us e a hotter plug.
WORN
Iden ti fied by severely eroded
or worn electrodes
• Caused by normal wear.
Should be rep laced.
PREIGNITION
Identified by melted electrodes
and possibly blistered Insulator.
Metallic deposits on insulator
indicate eng ine damage.
Caused by wrong type of fuel,
Incorrect ignition timing or
advance, too hot a plug, burned
valves or engine overheating.
Replace the plug.