My Rotax 912 in a Classic Mono has done about 360 hours. I had never
removed the magnetic plug until I saw Conrad Beale's article in Light
Aviation which showed a picture of where the plug was. I had previously
asked Skydrive but I don't think the chap I spoke to actually knew as I
still couldn't find it after speaking to him. The plug looked like a
hedgehog so I removed the swarf with a tissue and later washed out the
tissue in petrol with a small magnet in the bowl, which collected all
the swarf again. I sent this with my latest filter to ConAir and Conrad
advised that he should come and look at my engine. He removed the
gearbox and found significant pitting in the driven gear and advised
replacing the gear pair which he did. He said there was nothing worth
speaking of in the filter, but it had only done about 20 hours in the
engine. He thought the wear might be due to using Castrol GTX, which
used to be recommended, and I have now changed to Shell. The rest of
the engine was fine and it was clear that the source of the debris was
the gearbox.
It was very interesting to see Conrad working on the engine. He was
very quick and exceedingly careful and in particular he took enormous
trouble to ensure that all air was removed from the cooling system, and
then after running the engine did a further air bleed. This made me
wonder whether those who are having cooling problems may have got air in
their cooling system. A slight leak on the suction side of the water
pump could cause air to accumulate in the high spot above the starboard
radiator and prevent proper circulation. Although mine doesn't have
one, some people drilled a small hole in the radiator outlet pipe so
that they could bleed out the air by sliding the hose to the end of the
pipe, but not off, and subsequently the hole was covered by the hose and
the hose clip. Incidentally Conrad's hourly charges are very
reasonable, but at 81p a mile (which includes his own time when
travelling) travelling can add up and in my case, with two visits being
necessary, it was the largest item on the bill.
Frank Mycroft
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