Sea-doo Challenger 5896, Shop Manual

Page: 169 / 274

Section 08 ELECTRICAL
Sub-Section 04 (SPARK PLUGS)
08-04-2
DISASSEMBLY
First unscrew the spark plug one turn.
Clean the spark plug and cylinder head with pres-
surize air then completely unscrew.
HEAT RANGE
The proper heat range of the spark plugs is deter-
mined by the spark plugs ability to dissipate the
heat generated by combustion.
The longer the heat path between the electrode
tip to the plug shell, the hotter the spark plug op-
erating temperature will be – and inversely, the
shorter the heat path, the colder the operating
temperature will be.
A “cold” type plug has a relatively short insulator
nose and transfers heat very rapidly into the cylin-
der head.
Such a plug is used in heavy duty or continuous
high speed operation to avoid overheating.
The “hot” type plug has a longer insulator nose
and transfers heat more slowly away from its fir-
ing end. It runs hotter and burns off combustion
deposits which might tend to foul the plug during
prolonged idle or low speed operation.
1. Cold
2. Hot
CAUTION : Severe engine damage might
occur if a wrong heat range plug is used.
A too “hot” plug will result in overheating and pre-
ignition, etc.
A too “cold” plug will result in fouling (shorting
the spark plug) or may create carbon build up
which can heat up red-hot and cause pre-ignition
or detonation.
FOULING
Fouling of the spark plug is indicated by irregular
running of the engine, decreased engine speed
due to misfiring, reduced performance, and in-
creased fuel consumption. This is due to a loss of
c o m p r e s s i o n . O t h e r p o s s i b l e c a u s e s
are : prolonged idling, or running on a too rich mix-
ture due to a faulty carburetor adjustment or incor-
rect fuel. The plug face of a fouled spark plug has
either a dry coating of soot or an oily, glossy coat-
ing given by an excess either of oil or of oil with
soot. Such coatings form a conductive connection
between the center electrode and ground.
SPARK PLUG ANALYSIS
1. Overheated (light grey)
2. Normal (brownish)
3. Fouled (black)
The plug face (and piston dome) reveals the con-
dition of the engine, operating condition, method
of driving and fuel mixture. For this reason it is
advisable to inspect the spark plug at regular inter-
vals, examining the plug face (i.e. the part of the
plug projecting into the combustion chamber) and
the piston dome.
SPARK PLUG INSTALLATION
Prior to installation make sure that contact surfac-
es of the cylinder head and spark plug are free of
grime.
1. Using a wire feeler gauge, set electrode gap ac-
cording to the following chart.
2. Apply anti-seize lubricant over the spark plug
threads to prevent possible seizure.
3. Hand screw spark plug into cylinder head and
tighten with a torque wrench and a proper
socket.
A00E09A
1 2
-
A00E0AA
1 2 3