Here's one book every dedicated Vintagent should own. Originally titled 'Motorcycles and Side Cars', later amended to add 'Cyclecars' in the 1919 third edition, 'Early Motorcycles', published by the Norman W. Henley Publishing Co., appeared in 1914. 
Victor W. Pagé, Mechanical Engineer (M.E.), seemed to be a one-man mechanical explicator, having written 'The Modern Gas Tractor', 'The Modern Automobile', 'Automobile Questions and Answers', etc, all in those very early days when an 'owner's manual' was nonexistent, and a lot of bad advice was available in the many paper publications of the day.
I especially love some of the 'speed tuning' secrets from the pre-WW1 period, when drilling everything - pistons, con-rods, barrels, engine plates, valve stems - seemed to be the hot ticket.
'Early Motorcycles' is a huge book by contemporary standards, 550 pages long with over 350 illustrations, most contributed by motorcycle manufacturers themselves - Indian, Schickel, Reading-Standard, Rudge, Triumph, Bosch - and in the parlance of the day, the book had "the most valuable series of Drawings pertaining to Motorcycle Design and Construction ever published." Which may well have been true in the day; in England one could have purchased 'Motorcycle Repair and Upkeep' and many more titles by 1914, but they are dwarfed by Pagé's efforts. The illustrations are beautiful in themselves, carefully drawn and intended to enlighten the viewer technically with their attention to detail.
The list of topics is intriguing in itself, and hints to how green was the industry at that moment, and the vast number of options being explored by mechanically-inclined home inventors.
The book illustrates about 18 different configurations of engine placement alone - only one of which is in the eventual 'normal position' in the middle of a diamond frame. Like the dinosaurs, the motorcycle family tree had a lot of freakish oddballs vying for customers in the 'Noughts and 'Teens. Design started to settle down by the 1920's, but thankfully creative thinkers continued to explore other solutions to the two-wheeled question into the 1930's and beyond, although we seem to have been in a period of extreme stagnation since the 1980's, by comparison.
Chapter 1: Motorcycle Development and Design. The industry had been around for 30 years, since the Hillebrand & Wolfmuller became the first series-produced two-wheeler, but quite a few problems plagued these early beasts, most notably the inevitablity of catching fire due to 'surface carbs' becoming torches, and losing sparks due to inadequate ignition design. By the time Bosch began to supply a decent magneto, the industry was already 25 years old, and it took a few years yet before this technical leap eliminated the early battery-coil ignition.
Chapter 2: The Motorcycle Power Plant Group. This explores the basics of two- and four-stroke engines, then illustrates a few of the thousand variations on the theme, including early efforts at water-cooling by the likes of Scott and Precision (who used two little radiators like earmuffs on the engine).
Chapter 3: Construction and Design of Engine Parts. Goes into depth with good, clear illustrations of oil pumps, crankshafts, pistons, rods, gearboxes (both planetary and sliding-dog), etc.
I could certainly go on, but I'll skip to the best bit; as copyright ran out 30 years ago on Pagé's book, it has been reprinted several times since the 1970's, and can be found easily and cheaply from Amazon.com and other sources, for about $22. Buy it!
