Hmmm, let's see here. It does it while coasting.....as in when you're in Neutral or when you're in gear and engine braking? Have you tried replicating this if you have the clutch handle pulled in? If it's when the clutch handle is pulled (as it should be if coasting), then it's unlikely the clutch that's the issue here as half of it would be free-wheeling. Not unheard of, but not likely either. Time to turn to other issues. And considering you have 16k+ miles on the bike, when was the last time the chain and sprockets were replaced? I ask that because in a vast majority of these types of scenarios, it's the chain/sprocket that's lurching from tight spots and you feel it. Or it could be that the tires/wheels have a flat spot and that's what you feel.
- Check the wheels/tires for roundness
- Check the chain for tight spots are it goes around
- Check that the chain/sprockets are smooth when they mess together and aren't hitting any bolts/nuts/pieces in sprocket cover
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.