Is the replacement armature absolutely identical to the armature that was removed? There were variations over the years.
Is your loco smoke in tender, or smoke in boiler? In other words, where is the reverse unit located?
Does the armature turn freely when it it installed?
Why was the armature replaced? Why were the bushings replaced?
Are you applying power through the reverse unit first?
This motor is series wound. That means the power goes through the field, then through the armature, then back to the power source.
The more information you give, the better we can figure out what is wrong.
