It does it while cruising or engine braking, but not when coasting with the clutch handle is squeezed or in neutral. I may have said that ass backwards before. That's the main reason I assumed it wasn't the wheels/tires.
In all honesty, the chain and sprockets are from when I did the conversion, which was pretty much off the showroom floor. I like to think I'm pretty good at keeping it cleaned and lubed. But I really didn't know what to expect to get out of it. But by the sounds of it, I'm probably overdue.
I guess I assumed if it was the chain and sprockets it would do it while coasting as well.
So, when coating with the clutch pulled in, the chain and sprockets are freewheeling around and there's little tension on the chain. It all other circumstances there's tension on one run of the chain or the other. If tight spots exists in it, they will be felt in the zones. And depeding on how you have ridden over that 16,000 miles, you may have one area of the chain that has stretched more that another creating that tight spot. Until you measure the chain you can't tell. In a lot of cases, lifting the rear end and spinning the wheel by hand will let you visually see how the chain reacts when going around.
But given the nature of this thread/problem, that should be the first thing to replace to address the issue.