It's always ok to run it out of the box. However if you want some extra zip, do the following:
1. Pull motor apart, remove plastic / Phenellic washer. It does nothing but rob power.
2. Run a ball point pen through the grooves on the commutator. This will smooth any rough edges that may drag on the brushes.
3. Apply one drop of bearing oil to each bearing.
4. Re-Assemble and run motor at 4v for about 4 mins to seat brushes and generally get everything broken in.