Hi! Dave
I'm Not a Rotax Man But there's a thread on this problem in prior
messages ....lots of them. Get the engine turning over without the mag.
Switches on, then drop one switch followed by the other, can't remember
where the choke was to be set though. The other serious factor was to do
with the sprag clutch since the rough running on start up may be
exercising it beyond it's capability and so need it replacing.
Search the Archives there's many messages, I think it is to do with the
ignition timing being so advanced it is firing against the starter
before top dead centre and so the energy generated from the first
charged cylinder is insufficient to get the next one over TDC which
re-occurs adinfinitum. However you must read up to get the choke
procedure.
Regards
Bob Harrison G-PTAG Europa 337 MKI/Jabiru 3300
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of David
DeFord
Subject: Europa-List: bad cold starts
<davedeford@comcast.net>
When it was new, our 912S started as prescribed by Rotax when cold,
i.e.,
full choke with throttle fully closed. Opening the throttle even
slightly
would kill the engine, whenever the choke was applied. Over time (400
hours), it began to need just a bit of throttle along with the choke, in
order to start. Now it runs very roughly on a cold start with full
choke,
and will die after a few seconds of this (if we can stand it) unless the
throttle is opened more than 1/4 inch. It then runs perfectly smoothly,
---From idle to full throttle, without the choke. Unfortunately, opening
the
throttle this much causes the shaking to become so violent (momentarily,
until it becomes suddenly smooth) that it typically dislodges the
muffler
---From exhaust header pipes. It starts just fine without the choke, once
it
is warm.
Please don't bother to suggest balancing the carburetors, which we have
done
very precisely (witness the very smooth running without the choke). We
have
partially disassembled the carburetors and cleaned all of the jets with
carb
cleaner (though there was no sign of any contamination or blockage).
Mag
drop on both sides is fine, compression is like new, and we have never
experienced any kickback on starting. We have searched in vain for any
vacuum leaks, and the float needles seem to be keeping the float bowls
filled properly.
We feel that we have exhausted all of the reasonable possibilities, and
so
are open to bizarre and unlikely suggestions as well at this point!
Dave DeFord
N135TD (monowheel XS, 912S, Airmaster)
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