Disassembly; Heat Range; Fouling; Spark Plug Analysis - BOMBARDIER ski-doo Tundra Scandic 2004 Series Shop Manual

DISASSEMBLY

First unscrew the spark plug 1 turn.
Clean the spark plug and cylinder head with pres-
surized air, then completely unscrew.
WARNING
Whenever using compressed air, always wear
protective eye wear.

HEAT RANGE

The proper operating temperature or heat range of
the spark plugs is determined by the spark plug
ability to dissipate the heat generated by combus-
tion.
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 firing
end. It runs hotter and burns off combustion de-
posits which might tend to foul the plug during
prolonged idle or low speed operation.
1. Cold
2. Hot
MMR2004-131_06_03A.FM
Section 06 ELECTRICAL
Subsection 03 (SPARK PLUGS)
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 det-
onation.

FOULING

Fouling of the spark plug is indicated by irregular
running of the engine, decreased engine speed due
to misfiring, reduced performance, and increased
fuel consumption. This is due to a loss of compres-
sion. Other possible causes are: prolonged idling,
or running on a too rich mixture due to a faulty car-
buretor adjustment or incorrect fuel and/or fuel mix-
ing. The plug face of a fouled spark plug has either
a dry coating of soot or an oily, glossy coating 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 electrode and piston dome reveal the
condition 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 electrode and the piston
dome.
06-03-3