If you have a picture of the spots, that would help.
I doubt it's acne. It's more likely it's pyoderma - which needs to be treated via a prescription. Also, pyoderma is always secondary to something else like allergies, Cushings, thyroid...etc...
Does he chew or lick his paws? Where does he try to itch and is it year round?
For allergy info, go here:
http://www.yorkietalk.com/forums/die...tart-here.html