At 32 pages in length, it seems more like a cottage industry publication. Considering it was made in 1967, most likely it uses resistor speed control or no speed control at all.
As always Lyle, a neat find. > Product Details > > Titled: The Electric Motorcycle: A Builder's Manual > Unknown Binding: 32 pages > Publisher: Published by arrangement with "The Printer" > (January 1, 1967) > Language: English > ASIN: B0007HY4PS
