I've kinda always figured the Klingons that were investigating V'Ger were Klingon Defense Force ships, and sort of the equivalent of the poor bastards in the helicopters with the signal lights in the movie Independence Day
. They weren't there because they
wanted to attack, or were looking for treasure, or anything else. They were there because the Klingon government said, "go find out what that is and if it poses a threat or can be turned to our use" and so they followed orders.