Pete,
I had the same issue with the vibration when I got over 5000 RPM. Did an
analysis
which I include as attachment. You can see how the vibration spikes as the
engine RPM crosses 5000 RPM and it is indeed a peak corresponding to the engine
RPM frequency.
Clive Sutton had a theory that maybe the carburetors where resonating and
causing
issues.
According to RPX (DynaVibe) they indicated it was a carb balance issue at those
RPM. Bud once had a writeup on how he had issues with carbs not working in
unison
because of age and only going to new carbs solved the issue. Since the carbs
were a bit old that is certainly a possibility.
But I have to report that I bought a new engine and the vibration is gone.
Can I conclude it was a problem with the engine? no I can't because before
before
I flew the airplane with the new engine I removed the cone K&N air filters
I had and installed the cold air plenum (too many changes). So three possible
reasons:
1.- Something off with the old overhauled engine (kind of broad)
2.- Old carburetors coming out of balance at high end
3.- Vibration on the supported carburetors. I was told my carb support spring
were
a little soft.
For some time I thought the culprit could be something in the airframe
resonating
but with the vibration going away with the engine change that is not high on
my list.
I hope this helps.
Chris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=506582#506582
Attachments:
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