Turn the crank very slowly and shift from the next to largest cog to the largest cog. As you shift, watch the chain between the top of the pulley and the bottom of the big cog. There needs to be enough room between the the top pulley and the teeth of the big cog for the chain to pass through as the shift is made. If there isn't you'll see and hear it as it forces its way between the two bumping the pulley, cage and RD .