My thanks to everyone who came up with suggestions. Some of these I had already
tried, but what seems to have worked for me are two ideas. the first from Mike
Gegory, our esteemed safety officer was to use a radio tuned to a distant
station,
and with the sqawk turned up enough to be able to detect mag circuit noise
to determine whether this nopise continued when the mags were "switched off".
This is the equivalent to seeing whether you have a spark on an uncooperative
outboard or lawnmower, and immediately indicated that the mag circuits (or
circuit) were still working in spite of being switched off. I then went for
the suggestion of Bob Jacobsen who described an identical problem with his 912S
which he eventually found to be due to a faulty connection between the mag
leads and the ignition connector on top of the engine. I have replaced the
bullet
push in connectors at this point with hard wiring and my problem has gone
away. I did not find an obviously faulty joint (unlike Bob) but assume that the
connectors were giving an indifferent or highish resistanc join up which still
allowed enough of a spark to keep the engine going when hot. Of course as
my problem was intermittent it is a little early to pronounce a cure after only
two trial flights but if you hear no more the cure is permanent! David Joyce
G-XSDJ
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