I should just qualify Mark's statement about the factory demonstrator having a
'similar problem' with regard to mag drops. The 914 engined demonstrator
exhibits
a larger mag drop on one mag relative to the other but both are within limits
(300 rpm and 150 rpm difference). This is normal on the 914 as one mag runs
all upper plugs and the other all the lower plugs. Due to the geometry of
the cylinders, when one of the plugs ignites the mixture, it results in a
different
flame path to that of the other, hence the difference in mag drop.
One of the factors that should not be ignored is to check the balance of the
carburettors.
A mis-balance could result in one bank of cylinders or even one cylinder
causing the problem. We shall investigate this on Mark's engine before
anything else.
Regards
Andy Draper
>>> "Mark Chetwynd-Talbot" <markt@avnet.co.uk> 06/05/03 11:55am >>>
This does not seem to be an isolated case. I have had a mag drop
'on the margin' for many months and I have now asked Andy at the
factory to see if he can come up with a cure. When I spoke to him
earlier this week he did mention that the factory demonstrator
was also suffering a similar problem! So, when anyone comes up
with a solution, please let everyone know about it!
Mark G-CHET
-----Original Message-----
Hello group,
I long for a good old reliable Lycoming engine! My 914 is now
failing the mag
check and everything I try has actually made it worse. I have
consulted with
Rotax and they have suggested several things - cleaning up the
connections at
the plug wires, swapping plugs too to bottom to see if the
situation reverses
(indicating a plug problem), changing the plugs to new.
The problem is I get a mag drop of 300 on circuit B and now 500
on circuit A.
At this point, with cleaned up wires, new plugs - it runs rough
on mags A
and B one at a time, with the large drop coming on A still. I now
cannot fly -
I
think it is even running rough with both mags on.
The latest suggestion is to check and clean up the ignition
ground bolt by
the electronic boxes. Then, it is to again check the carb synch -
THEN they need
to "see the engine", which can be a big problem where I live,
since I won't
fly it until I figure out what is wrong.
One other thing I can say is I don't think I ever had a very good
mag drop
since new. It was less than the limit of 300, but not by much
compared to what
most people are telling me.
Any suggestions out there besides replacing the engine with one
that a
control freak like me can adjust!
Dave
A227
Mini U2 (grounded)
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