You are hearing your primary chain (as you thought). The blast does not have an inspection cover, so you just need to adjust the bolt underneath, which puts pressure on the chain via a shoe. What I would do is adjust it until you no longer hear the clanking, then go for a ride. clanking comes back adjust slightly in Its better to have it lose than tight.
The pushrods are on the opposite side of the inspection cover. The inspection cover only allows you to adjust the clutch, and add oil.