just curious, but what happens if you pull the air intake line off the carbs
and do the test. Other thing
is have you or the rotax man checked the timing. If the timing is late then
you will get incomplete combustion of the fuel, and the extra plug firing
will help overcome the late spark. If its late timing
it wont hurt the engine, but it wont be at its best either.
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com]On Behalf Of Keith Hickling
Sent: Friday, 27 February 2009 2:56 PM
To: europa-list@matronics.com
Subject: Europa-List: large mag drop on both mags, 912uls
Hello all,
On first running my new 912 uls a couple of weeks ago, I got a mag drop pf
just over 500 rpm on one mag and just under 600 rpm on the other mag,
starting at 4000 rpm. All else was OK; oil temp and press, EGTs, CHTs etc,
and the engine ran quite smoothely; even on 1 mag with the rpm drop it was
not obviously rough or misfiring. Prop is Airmaster, operating correctly -
testing done on fine pitch.
Our local Rotax man thought it was probably not a real mag drop but a
tacho problem, though it sounded real. So yesterday we checked it with an
optical tacho and it was real. The optical tacho showed a rpm drop on the
prop from 1700 down to 1490, which is equivalent to a 500 rpm drop on the
engine.
Another rotax owner here suggested it might be the mag ground leads
shorting to the screen, as I had left the screen quite close to the end of
the wire where it enters the ignition modules. So today I stripped the
screen a bit further back, disconnected the screen ground and connected the
mag shorting wires to 2 temporary switches, bypassing the ignition switch
completely. This made no difference, still the same mag drop, eliminating
partial shorting of the mag wires as a cause.
The plug gaps are correct, and the plug colour looks OK. The throttle
cables are set correctly. The engine always starts first go, easily, and
runs smoothly. Our local engineers have no ideas, although they are not very
familiar with rotaxes. So I would really appreciate any advice on where to
go from here - what should I look at next?
Thanks,
Keith Hickling,
New Zealand,
Mono XS, Kit 613.
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