Have you check that the setting for rotor position is correct or not? How about normal vibration in steady stage and how much VPF in this?
I agree with Walt that more information would be needed such as:
- Drawing and measurement point.
- total free movement of rotor without bearing and how do you set the rotor position? is it a half of this value?
- How about flow, temp, pressure of this pump and performance curve respectively.
The VPF when coast down not talk too much as at that time, the flow is not stable and far from BEP.