Several of the members here got a chance to hear that noise on mine when we were in Eureka Springs, AR earlier this year. My starter quit working altogether on a rain gear stop. I had my starter replaced, and that solved the problem for about a day or 2. When I got back home, I had my local dealer check out the ACR's (automatic compression releases) and that was the problem, or at least the other part of the problem. Since having the ACR's replaced, I haven't had that problem anymore.
Just a few weeks ago, my friend was having the same problem on his Ultra with a 113" engine. It had the identical symptoms as mine, but they found that the problem was in the electronic throttle on his. They replaced the throttle by wire setup with what they told him was a new, upgraded setup. That fixed his problem.