go back vs hark back

go back and hark back both are verbs.

Word	Noun	Adjective	Verb	Adverb
go back	No	No	Yes	No
hark back	No	No	Yes	No

As verbs, hark back is a hypernym of go back; that is, hark back is a word with a broader meaning than go back:

Other hypernyms of go back include come back, recall, return.

go back (verb)	hark back (verb)
regain a former condition after a financial loss	go back to something earlier
return in thought or speech to something
belong to an earlier time