Then I shouldn't bother to suggest that the chokes themselves are unbalanced
or not operating on one side. OK, you've probably done this but it may be
instructive to find out which exhaust header pipes get hot during this
starting process.
Duncan McF.
----- Original Message -----
From: "David DeFord" <davedeford@comcast.net>
Subject: Europa-List: bad cold starts
>
> 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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