Yamaha jumping jacks

[Annie Grieshop]

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Good evening,

I had two tuning jobs yesterday that involved relatively new Yamaha
verticals - an M500 and an M450.  Both have very jumpy jacks (or, at least,
that's my analysis of why they're tending to double-strike, even when
well-regulated), and I'm wondering why.

Both have plastic jacks and synthetic buckskin.  The M500 had been treated
with something that looked graphite-like and was less jumpy than the M450,
which leads me to believe that the proper lubricant (or other treatment)
might solve the problem.  I would very much appreciate any suggestions as to
how to proceed.  Thanks!

Annie Grieshop
in the wilds of balmy Ioway, where winter is still in our future.....

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