Remi, Jean Philippe, and All,
To try to minimise the effect Remi has described, I have developed a
technique as part of my pre-flight walk-around. When I get to the business
end, I turn the prop several times in the normal direction of rotation and
then when it feels freed-up, I rotate it backwards to meet the compression
and at the same time, take up the 30 degs slack in the slipper clutch. I am
sure this technique helps and the amount of reverse rotation is not enough
to affect the oil priming. The other action I took when I replaced my 912
with a 912S, was to increase the magneto gaps to 0.020" (from 0.016"), which
has the effect of slightly reducing the amount of retardation at tick-over,
but probably has a minimal effect at >4,000 RPM. It also makes the
tick-over run much more smoothly. The increase of magneto gap was not my
idea, but it came from a Brit with well over 1,000 hours in Europas. If
anyone knows why Rotax set the mags at 0.012 to 0.016, please let me know.
(Apart from selling more sprag clutches, of course!)
Best wishes,
William
----- Original Message -----
From: "Rmi Guerner" <air.guerner@wanadoo.fr>
Sent: Monday, February 06, 2006 8:38 PM
Subject: Europa-List: Kick back is back
>
>
> Salut Jean Philippe,
>
> Je repond en anglais pour que tous en profitent. C=E2=80=99est mieux,
> n=E2=80=99est il pas ?
> The infamous kick back happens when the first cylinder to ignite does so
> before reaching top dead center (TDC =3D PMH in french) which is not
> unlikely with the spark advance set, by design, at 4 degrees before TDC,
> and not adjustable. Because the prop is driven through the slip clutch,
> there is no flywheel effect and the crankshaft stops immediately. Then the
> prop uses its own inertia to turn up to 30 degrees (slip clutch backlash)
> and violently hurts the dog. It is so violent that it can damage your
> exhaust, carburettor flanges and engine mount altogether, and possibly
> the engine itself. This happens mainly with the bigger displacement and
> higher compression 912S, but I experienced it once or twice with the 914
> too. Rotax allegedly solved the issue with a more powerful starter motor,
> but clearly the problem is still there with the new starter motor.
>
> Remi Guerner
>
> F-PGKL, XS S/N395 monowheel, 288 hours on a 914 + 91 hours since fitted
> with the 912S.
>
>
> From: NEEL Jean Philippe <jeanphilippeneel@yahoo.fr>
> Subject: RE: Europa-List: Kick back is back
>
> <jeanphilippeneel@yahoo.fr>
>
> Salut Remi
> S'agit il de battements generants des vibrations importantes empechant le
> demarrage?
>
> JP Neel F-PSLH 650h
>
>
> Rmi Guerner <air.guerner@wanadoo.fr> a crit :
>
>
> In spite of having the heavy duty starter, a 6 months old 28 Amp-hour
> battery,
> an ignition switch wired so that only one channel is energized during
> starting,
> pulling the choke only after a few prop turns, I experienced the infamous
> kick
> back again last week, during a few degrees above freezing cold start.
>
> To help solving this problem, I am thinking at replacing the low cost
> battery by
> a high performance one such as the Odyssey or Genesis. Any suggestion on
> where
> to find this sort of batteries in Europe ?
>
> Remi Guerner
>
>
> --
>
>
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