Keith,
I didn't notice what fuel you are running in on. 100LL aviation gas
gives less mag drop than the 92 to 94 RMS Premium fuel here in the
States. I must show my ignorance since most of my experience is with
the 914. I have yet to see a mag drop below 300 on Premium and even
less on Aviation Fuel. If the engine is running smooth as a sewing
machine on one mag, I would suspect the octane rating.
Hope it all works out. I used to think that if it didn't say Lycoming
or Continental, it didn't belong on an airplane. These Rotax's have
changed my opinion. My experience is they start and run well when
properly serviced right out of the box. Just wish they were fuel
injected.
Bud Yerly
Custom Flight Creations.
----- Original Message -----
From: Keith Hickling<mailto:keithhickling@clear.net.nz>
To: europa-list@matronics.com<mailto:europa-list@matronics.com>
Sent: Thursday, February 26, 2009 11:56 PM
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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