Sea-doo Bombardier, Owner'S Handbook Manual, Page: 40 / 123

03-11
SECTION 03 - ENGINE PREPARATION
With all operating parameters correct, normal
combustion will take place. However, if for some
reason the temperature inside the cylinder is in-
creased during combustion, abnormal combus-
tion will occur and lead to serious engine damage.
Detonation
In detonation, the spark plug initiates burning and
the air/fuel mixture starts to burn in the usual
manner but as combustion continues, the heat
generated affects the large portion of the yet un-
burned air/fuel mixture.
This unburned mixture temperature becomes so
high that it burns spontaneously creating high-velocity
pressure waves within the combustion chamber.
These shock waves can sometimes be heard as
“pinging” (this pinging is especially detrimental to
engines with raised compression ratios). While
these shock waves can be detrimental to the me-
chanical integrity of the engine, it is the genera-
tion of excessive heat that causes most problems
in 2-stroke. For many various reasons the piston
may expand excessively causing a seizure or the
piston dome may in fact melt. The melting will oc-
cur at the hottest points, which will be right below
the spark plug and around the edge of the piston,
often at a ring locating pin. If allowed to continue,
a hole may melt completely through the top of the
piston.
F01D5JA
...until mixture
is completely
burnt
F01D5GA
Spark occurs
as piston
approches Top
Dead Center
F01D5KA
...heat and
pressure rapidly
build up...
✩
F01D5LA
...remaining
unburned
mixture burns
spontaneously...