Hi Fishwinker,
Been brooding about what could be causing your motor vibration ... and I'm still brooding ...
In the meantime, take a look at 4yanx's post from a while back and see if it applies.
04-27-05: 4yanx
"As a further aside, we've found that the proper "tension" placed on the nose end screw is such that it the cupped end just seats onto the end of the rotor spindle and allows free travel of the "springy" doo-dad (less than a millimeter). Too little tension causes slop and too much causes restriction. It is a very fine line and impossible to "see". It helps when you get it right to have one person hold the motor casing with one hand, and a small screwdriver set in the slotted end of the screw with the other, while a second person FIRMLY tightens the hold down nut. In our experience, tightening that nut otherwise almost always results in the screw tightening a bit along with it and mucking up the works. Too, if the nut is not secured tightly enough, it backs off - the screw along with it. On out first couple, the doo-dad was so frozen that we didn’t even know it was supposed to “give”. Getting the proper tension was a BEAR until we discovered that."
Is there a numeric designation on the GL Delta Lady?