John
I have been chasing this exact problem since May 20th and finally it looks like
it may be cured, but without actually finding anything wrong.
I will explain.
At 4900 rpm and 25" manifold pressure it was smooth as you could want. At 4900
rpm and 24" map down to 18" map and really severe vibration.
Over the next few weeks I checked and test flew
Carb balance
Replaced the carb needles and jets
Changed both the carbs to a couple of spares
Flew using only one then the other mag
Checked the whole exhaust system
Replaced the whole exhaust system for an old spare setup
Checked over the whole Airmaster propeller assembly
Checked cylinder pressures
Checked the engine mounting rubbers
Checked for anything touching or loose
All of these things made absolutely no difference to the manner or severity of
the vibration.
Finally after advice from a Rotax expert service agent in the UK I removed the
gearbox and took it to him. He took it apart but couldn't find anything wrong.
I got him to replace the bellville washers and the front bearing as it was all
apart.
Upon reassembly it now runs smooth again, so probably or maybe it was the
gearbox.
I am still very wary at the moment but I am hoping the problem is solved.
Dave Watts
G-BXDY Classic MonoWheel
2150 hrs airframe 1150 hrs 912S Rotax engine
> On 13 Jul 2015, at 21:29, JohnFrance <77alembert@gmail.com> wrote:
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> Hi All,
> during a recent flight I experienced (propeller!) vibration at the start of
> the
descent when I reduced power. This was after about two hours in cruise flight.
The frequency was quite high and I could feel a tingling sensation in the
feet in contact with the rudder pedals which makes me think the vibration is
coming
---From the propeller/engine combination.
> Upon landing I made a close inspection of the propeller and everything seemed
normal except for some flies and bugs. After cleaning, during the next flight
I experienced the same problem. The vibration is at its worst at 4800 rpm and
reduces slightly at 5000 but it is still noticeable.
> Before I start taking everything to pieces does anyone have an idea what could
cause this sudden change?
> Regards,
> John
>
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> Europa mono Nr 192
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> Read this topic online here:
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> http://forums.matronics.com/viewtopic.php?p=444702#444702
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