You should make sure that the carb with the broken cable is in the "normal, running" position.
On a well-tuned airhead, you only need to enrich one side to get it to start.
But the best thing to do, is remove the lever and cables, (they make a blanking cap for the left perch, P/N 32 72 1 234 724), get some welding rod and bend it up like in the picture. One for each side, or like I said, you only really need one.