Hi,

I break in my 700 motors by running them half submerged (just the brushed end, NOT the ballbearing) on a low voltage, just enough to let the motor run.
As the brushes are very hard and the motor runs very slow, it takes several hours to break in the brushes.
Check regulary and don't walk away to go do something else!

When the water begins to turn dark(ish), I cut the power and take the motor out and check if the brushes are seated on the commutor curve, if i'm happy with the result, I let the motor dry thoroughly, overnight on the central heating will do fine, and lightly oil the rear bushing.
If the brushes are not to my satisfaction, I continue the process.

As the water softens the brushes, make sure they are completely dry before running the motor at a higher voltage, or you'll wear them down excessively!

Regards, Jan.