Hi Ron
I think it must be the primary chain. The motor went into the bike in the mid 1990s as an unsuccessful attempt at a 730cc or so motor with a large engine sprocket. Perhaps the current chain has been predicated on the longer one required for the large sprocket, I can't remember off hand. The gearbox retaining bolts are further to the front than the rear in their slots, the gearbox isn't in an extreme position.