Hi William
>This winter, I have been having difficulty starting when cold, because of
what would appear to be early detonation. The engine fires and stops the
rotation dead. This can happen several times before it starts. I can't
remember having this problem last winter or the one before that. Has any
one else experienced this, because I am sure it can't be doing the engine,
or mount, much good. Otherwise, when running it seems to be functioning
well. Warm starts are without choke are OK. Can the timing slip on a 912?<
The pick-up coils for the ignition determine the timing. As far as I am
aware there is no adjustment in angular position to adjust timing. However
the setting of clearance from the flywheel will affect the timing very
slightly. One idea to help prevent the starting problem you describe is to
make sure the starter is up to max motoring speed before selecting full
choke. This way there might be enough inertia to get the engine closer to
TDC before ignition. The problem you describe is also more likely to happen
if the battery is not providing quite as much cranking energy as normal.
This might be why it happens more on colds starts. Cold oil and a battery
that has not received any charge for a few weeks both contribute to a slower
cranking speed. An external battery for the first flight of the day may help
to improve starting performance and will also help to keep your expensive
a/c battery in peak condition. The problem tends to be even more noticeable
with 912S engines due to the higher compression
Nigel Charles
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