Originally published under the title The Book of the BSA Twins by W. C. Haycraft this book is one of The Motorcyclist's Library series published in the USA by Floyd Clymer by arrangement with the original publishers Pitman Ltd. of London, England. It includes complete technical data, service and maintenance information and detailed instructions for the repair and overhaul of the major mechanical and electrical components for all models of BSA pre-unit twin cylinder motorcycles from 1948 through 1962. There is adequate detailed text and diagrams to assist in major refurbishing such as an engine rebuild or even a complete renovation. This is a - must have - reference for any BSA enthusiast and would certainly assist in helping any potential purchaser better understand the inner workings prior purchasing of one of these classic motorcycles. Applicable to all 500cc and 650cc variations of the A7 and A10 pre-unit OHV twins this publication has been out-of-print and unavailable for many years and is becoming increasingly more difficult to find on the secondary market and we are pleased to be able to offer this reproduction as a service to all BSA enthusiasts worldwide.