Here's the history I've received from a close relative of Baker Williams, the man who produced these mini bikes. His son's first bike was a Go Kart Co. Green Enduro powered by a 2 1/2hp Clinton. He bought it with paper route money. They went to the factory in Azusa to buy a go kart but fell in love with the mini bikes instead. He learned welding, engine rebuilding and porting on that bike. Later it got a jack shaft and a 700 West Bend. Then they built their own prototype with a hard tail and the Earls fork. 2 More prototypes and racing were to come to get the desired geometry of the frame, fork, steering, rake and trail, and swing arm position. A main concern and design feature was the concentric swing arm and jack shaft, keeping chain tension consistent. Simplicity was also a major goal. A dozen or so experimental bikes were made with a lot of different features. One even folded to fit behind the seat of a 64 Porsche Cabriolet. It was too week for racing and turned into a parts donor as did some of the other attempts. Only 12 of the bikes in my photos were built and raced. About half of them can be accounted for so far. Little or no literature exists but it was confirmed there was a good article in Cycle World. We're trying to find the magazine. If I have any of this incorrect, I'm sure it will get straightened out. This is a great story and hopefully more info to come.