Yamaha CFlll Question

[Phil Bondi]

I am caring for one presently, and from G#5 to about D6 is noticeably 
lacking in sustain of any kind..almost like the damper is still on the 
strings. There is good tone, with no sustain.

Is there something I can do for these few notes to blend them in better?

The tech that normally has this piano in his possession does not like 
liquids..and I'm not sure this is really a hammer problem since there is 
good tone, but no sustain.

Any ideas?

Thanks,
-Phil Bondi(Fl)