Baldor Grinder Motor Noise

[Rata222]

Hi All.
I purchased a Baldor 7" Model 7306D Grinder -manufactured in the 1960's) to refurbish as a project.. I disassembled the motor to paint and replace the bearings. I had not run it much before the tear down - only to see that it worked. After reassembly, when I start the motor it makes a growling noise in the first moments of startup as shown in the linked video. Then it runs smoothly. I hadn't noticed this before the tear down - but it may have been present.
Is this normal? If not what would it be indicative of? The motor was very clean inside. I replaced the bearings with NTN bearings and original shims. After hearing the noise, I pulled the motor back a part to look it over again. I did not see any damage to the rotor or stator . Only a little area on the rotor as shown in the picture. Could this be the cause?
Any ideas as to what else may cause this noise? Or is does it sound normal?
Thanks for any help.

Video:

 

[benmychree]

I think that if the damage marked on the rotor made any difference, it would be noisy all the time. I'm wondering about the capacitor and starting switch.

 

[Nutfarmer]

Gg

 

[silence dogood]

I suspect that the contacts on the centrifugal switch in the motor are tarnished or burnt. Cleaning the contacts should help.

 

[Rata222]

I think that if the damage marked on the rotor made any difference, it would be noisy all the time. I'm wondering about the capacitor and starting switch.

I suspect that the contacts on the centrifugal switch in the motor are tarnished or burnt. Cleaning the contacts should help.

Thanks for the input.
I should have mentioned that I replaced the old 7.5 uf capacitor with a new AmRad 7.5 uf capacitor - since I had it apart. The first thing I did, after hearing that noise was put the old capacitor back in. No difference. Of coarse it could be a bad new capacitor. I assume the existing capacitor was correct. It was aerovox - which is the brand used by Baldor. The motors do not have a start switch.
It just sounded excessive to me - but maybe that sound is not uncommon?