Does Montresor explain why he wants to take revenge?
It is that he has no bona fide cause for revenge (one that he states) that makes this story so horrifying. By not identifying the cause for revenge, we cannot dismiss it as unworthy or outside of our range of experience. Instead, the revenge achieves a universality, a flaw of human character, or perhaps more aptly, a commonality of human emotion that Montressor works out for us that we, only in our unconscious, would dare to think about. Poe often treats such taboo subjects that he considers fundamental to human experience but too awful for a person to lay claim to. Indeed, in an essay on poetry he calls such horrific experiences and emotions "beautiful."
Unfortunately, the answer to your question is no. Montresor does not detail his reason for revenge other than to say that Fortunato had "done him a thousand injuries". He doesn't detail any single one, nor does he ever give any specific reason for his cruel revenge. It could be assumed that, as in many of Poe's tales, there is not actually any wrong deed done to lead to the horrible action, but there is nothing in writing to prove that.
the writer isn't reliable because montresor is writting the story after half a century. he just says that fortunato has injured and insulted him . i kept waiting the whole story to find out what did fortunato do but the writer didn't state it eventhough he said that a revenge is not worthy unless the victim understands his wrong and he didn't state it to justify his revenge.maybe montresor was just jealous of fortunato of being a connoissuer like him and maybe fortunato didn't insult montresor at all because when they meet in the festival fortunato greted him withwarmth.
based oN our discussiOn furtunatO insulted moNtressor to tHe extent thaT montressor's familY was incLuded...!! iT caUseD montressor to revenge.. (thiS is OnlY base on our discussion...)