Have you tried the Atlas Web site? There are a lot of exploded drawings in the "Parts" section. You will want the models that say "Japan" for the Kato built units.
You might try here: http://www.hoseeker.org/otherhotrains.html
Trying to do some maintenance/repairs on a late 1980's Atlas diesel with a Kato motor & mechanism.
Does anybody know where to find diagrams of the locomotive mechanism?
Thanks