Yamaha U1 practice rail adjustment

[J Patrick Draine]

I have a Yamaha U1 I service annually, but I found myself a bit confounded
by the middle pedal/practice (quiet) rail adjustment this time.When I opened
it up, the rail was "engaged", i.e. in the "down" position, muffling the
impact of the hammers on the strings, but the pedal was in the "up"
position.
I wasn't able to adjust the plastic nylon turnbuckle to get it to proper
specs.
Is it likely that the rail's spring is the culprit (fatigued and unable to
pull the rail up to proper position)? Do the turnbuckle's threads strip out?
Anyone know the know the threading dimensions of the parts (the threaded
wires, nuts, turnbuckle)?
Seems elementary (maybe I just needed another cup of coffee), but I need to
go back this afternoon and "get it right." Help greatly appreciated.
FYI, I did call Yamaha tech services but the promised "we'll have the tech
service rep call you back" call never happened.

Patrick Draine
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