Undetermined Noise

[zoom45]

I just returned from a 1700 mile (did the dragon and Smokies in Tennessee) ride on my 2000 Nomad 1500 (carbed) with 52,000 miles on it. Before I left, I had noticed a slight rattling sound at a certain speed but couldn't tell where it's coming from. I never noticed any power difference the entire trip. It sounds like two big washers that are loose on a bolt and rattling. It's only noticeable when you are cruising at 50-60. If I pull the clutch in I can't hear it and if I accelerate to a faster speed I can't hear it. It's only at a steady speed. I have looked everywhere and can't find anything loose. I can't touch anything while riding that seems to vibrate so it's hard to narrow down the location. I was wondering if the timing chain adjusters could be maxed out and do it? It almost sounds like a baffle plate in the muffler could be rattling. Has anyone experienced this or had problems with the adjusters? I talked to a Kawasaki dealer mechanic and he had never heard of it or had to replace any timing chain parts in a Nomad.
Thanks,
Zoom45 ???