Cushman engines
The first Cushman scooters were called "Autoglides" and they were powered by 1, 1.5, and 2 horsepower "Husky" engines. In 1938, the Husky got four horsepower. These engines had a vertical cylinder with a flat head and the spark plug on the front of the head. The head and block were cast iron. There was a detachable oil sump on the bottom and so they were called the "two-piece block Husky." It was a good engine in it's day and was fairly easy to repair.
In the mid 1940's Cushman dropped the Autoglide name and came out with the 50-series Cushmans, but they kept the 4 hp, 2-piece Husky.
About 1949* Cushman introduced a one-piece version of the Husky. The spark plug was moved to the center of the head. It came in 3.2, 4, 4.8, and 5 horsepower versions. Often, the horsepower rating depended more on regulations than actual power. Some states specified that you had to be 16 to ride a scooter with five or more horsepower.
About the middle of the run of 60-series scooters, Cushman introduce a new, more powerful, Husky. It was rated at 7.3 horsepower (5 in some states) and had a 2 7/8 bore. Because the cooling fins were different, it became known as the square-block Husky. By default, the earlier one-piece Husky became the "round block."
Early Cushman Eagles were often powered by round block engines with five horsepower, but the standard soon became a three-inch bore, 8 hp square block.
By 1960, Cushman had been sold to Outboard Marine Corperation, the company that made Johnson and Evinrude outboard motors. They set out to modernize the Eagle with an aluminum, overhead valve, nine horsepower engine with the cylinder tilted toward the front of the scooter. They called it the Super Husky, but it's usually referred to as "the OMC engine." The Eagles with these gleaming silver engines were called Silver Eagles. Some had electric starters.
Who knows where Cushman was heading. Was there to be a Golden Eagle? Was the two-speed transmission to be replaced with three or four gears? Unfortunately, scooter production ended in 1965.
Howard
*Dates are approximate, because Cushman didn't keep very good records.