The handle is just a couple of screws. No big deal. Just a simple cable.
It's an enrichment circuit though, so by "closed" do you mean engaged liek a choke plate being closed, or do you mean the enricher is closed i.e. normal running position?
If it's not pulled/engaged, just reach in to the carbs and pull the metal L shape back to slip it out of its retainer bracket. Then the ferrule (bead) on the carb side slides right out. Easy peasy. Push and pull cables are easier to do once the carbs are hanging out of the bike though.