I'm not sure if I have ever read any Silverberg. None of his novel titles ring any bells, but one did remind me of Bob Shaw's Night Walk, which I just added to my Kindle, so thanks for that.
As for the 2-strokes, I've ridden many over the years from 25cc to 750cc and the one abiding memory I have of them (apart from "ring-ding-ding-ding" and the smell) is the vibration. However, they were from an era when even the big 4 cylinder 4-strokes were "buzzy" and you had to go to 6 cylinders (CBX1000, Z1300, Benelli Sei) if you wanted smoothness.
The other problem I had with most of them was their size. At 6'4" they all felt like mopeds, even the H2's and the Kettles.
Yes, the singles were the buzziest, but that was the same on the XL600 as on the CR250 (both 48bhp). Parallel twins are better and triples even more so, but only with 120° cranks like the Jota. The RD500 and the RG500 were about as smooth as any modern bike, but then the RD had a balance shaft and the RG didn't need one due to the square design.
The powerband on 2-strokes is addictive though.