Hi all,
I am the unlucky owner of an engine (912ULS) which is prone to kick
back on cold starts. During the 6 years and 500 hours of operation I
have tried EVERYTHING suggested by the Rotax factory, Rotax
distributors worldwide and operators writing on this forum, including
the SoftStart module from Conair. All these alleged solutions have had
some positive effect such as a reduced occurence of the kick-back and
a less violent one, but none of them, even when combined together,
managed to withdraw the kick-back completely.
Now the good news is that Rotax has introduced (at last!) new ignition
modules and a new flywheel hub to fix this problem (see SI-912-020
R3). The new ignition modules do exactly what the SoftStart does: they
prevent the ignition timing to switch to the 26 degree before TDC as
long as the starter motor is activated. In fact the switching to 26
degrees occurs a few seconds after the starter button is released. The
new flywheel hub (see attached drawing) features extended trigger
cams giving a 3 degrees after TDC ignition timing during the cranking
phase instead of 4 degrees before TDC. Obviously the engine cannot
kick back as long as the ignition happens after TDC, so I strongly
believe this change is a radical solution to the kick-back problem. I
do not need the new ignition modules as I already have the SoftStart.
So I will replace the flywheel hub only.
Here are my questions:
1. The price of the new flywheel hub is 315 Euros, French VAT
included. To avoid spending that amount, I am thinking at modifying
the existing hub. I would weld a 7 millimeter extension to the
trigger cam trailing edge and machine it on a lathe or adjust it with
a file. It is not necessary to modify both cams as only one is used
with the SoftStart module, the other one being inactive during the
cranking phase. Does anyone know what material (presumably a variety
of ferromagnetic steel) the hub is made of? Any suggestion on how to
do this cam extension?
2. Removing the flywheel hub is very easy, even without removing the
engine from the aircraft. But a special tool is needed to extract the
hub from the crankshaft tapered end. This tool (Rotax P/N 877377) cost
76 Euros VAT included. This is not very expensive but is too much for
a tool I intend to use only once! Does any one have this tool
available and would lend it to me? Are there many other owners who
want to do this mod? If yes we could ask the Europa Club to purchase
the tool for use by the members.
Waiting for your answers
Regards
Remi Guerner
F-PGKL
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