Are reservations required for the April 18th Event ?
Only if you want to stay in one of their cabins. Otherwise, they have free-range camping - put your tent down where ever you find a convenient space - and no reservations are needed for that.
Even if their cabins are full, Tellico Plains has a lot of other options. I know several people who come for the roads and the friendship, but prefer to stay at other locations due to privacy, sleeping needs, etc.
One other thing. Except for coffee, food is on-you-own at Hunts Lodge. But for the spring and fall get-togethers, Lori cooks for the entire crew on Saturday - breakfast and dinner. It's usually standard breakfast fare and dinner is usually barbecue. But Lori is a *great* cook. And she says that she actually enjoys cooking for 40 or 50 people. Masochist.
One (more) other thing, these events are usually referred to as "SME's". The acronym stands for SabMagEvent - referring to the fact that the group started as a collection of riders of old 80's Honda Sabres and Magnas. But nowadays those old bikes are in the minority. You'll still find lots of Hondas, of course, but a lot of the riders have switched over to all kinds of brands - Triumphs, Suzukis, BMW's, Yamahas, Kawasaki's, even (shudder) a Harley. (We call him Harley Boy, and he takes it well).