Kress Spindle speed fluctuatling randomly?

[Voicecoil]

Thank you.

I bought new brushes and installed them (the old ones were only a 3rd of length left).

Sounds different and wavers a bit on start up.

Do they need a bedding in period?

They can do in order to make full contact with the commutator: the shape of the end of the brush doesn't always match it exactly particularly if old.