Do alternator brushes need to "seat" to the rotor?

Been fighting a charging problem on this Maxim, finally got an ohm-meter with a zero adjust so I could get some good readings, and the rotor is out of spec (8 ohms) at the connector to the regulator. Rotor itself is within spec when placing a lead directly on each ring, so I'm thinking "piece of cake". Clean the regulator connector, clean the separate connector that leads to the brushes, replace the brushes, clean the two rings on the rotor, and still can't get this thing to measure within spec. Finally, out of desperation, I sanded the two tips of the brushes, put the housing back on and cranked it over a few times, and finally got it to measure at 4.9 ohms (spec is 4.5 +/- 10%), so success. Ran out of daylight before I could get the bike charged, started, and verify that it actually charges now, but I'm hopeful.

Anyway, is this common? Do the brushes need to seat to the rotor?

Also, the brushes are made of graphite, right? Which must be conductive, so the graphite residue that accumulates on the rotor rings should not be a cause for concern?

 

most brushes on electrical apparatus need bedding in.
wee did this (before i retired) on larger machines by placing a piece of emmery cloth between the brush and the rotor then moving it back and forth to concave the end of the brush ,to be the same shape as the rotor or commutator.
i belive the slip rings are flat on your machine ,so bedding the brush in would not be nessesery, except maybe to clean the end prior to fitting

brushes are made of carbon, so the carbon dust that accumulates between the rings ,would be conductive, so keeping it cleac is a must.
stu