Fluttering keys is a common problem with Aeolian actions.  Generally,
the cause is a combination of porous pouches and excessive valve travel.

That the fluttering occurs only on specific notes suggests lack of
precision and/or thoroughness in a previous rebuilding.  Although
fluttering may be caused by porous pouches alone, when excessive
valve travel is present, the valve when fluttering may never reach
the extremity of its travel in either direction.

#65 bleeds, a common size, require airtight pouches for optimum
performance.  Whatever Aeolian used originally to seal its pouches
(egg white?) usually seems to have evaporated without liquefying,
leaving no trace; the porosity of the effectively unsealed pouches
will vary from one to another even when the finest leather is used.
Two thin coats of "Best Test" rubber cement seems to be the most often
recommended treatment.

Reducing valve travel is accomplished by adding paper punchings to
those already present.  Travel distances of .032" to .040 have been
suggested by various rebuilders.  Cross valves controlling large
pneumatics of graduated sizes would logically require greater travel
than regular type valves in a stack having small pneumatics all of the
same size.

Personally, I have never sought to find the optimal minimum travel,
not wanting to redo a set should I have tried too short a distance.
Usually, however, subtracting a few thousandths will result in marked
improvement owing to greater efficiency.

It goes without saying that the old, dried-out burnt shellac used to
seal the lower valve plates to the wood needs to be replaced with a
sealer that will never completely harden, such as silicone rubber but
_never_ PVC-E glue.  Beyond that, there is the question of resurfacing
and re-plating (if not aluminum) the lower valve plates.  This type
of work provides the inexperienced and often hurried rebuilder ample
opportunity to really mess things up!

Finally, the fluttering problem may never be solved for certain rolls
other than original Duo-Art production.  For example, when a roll is
recut using dull punches and/or certain types of paper, the paper may
pucker as the punch goes through, after which the pucker will close in,
resulting in a smaller hole.  Punch sizes and spacing are found to
vary, too.

Jeffrey R. Wood