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Yamaha Ascot Scrambler 1963

Southern California's Ascot Park was the hotbed of flat-track racing in the western United States in the 60s and 70s. AMA rules required first year professional riders to compete on 250cc machines in the novice class until they made enough advancement points to move up to the Amateur class. Amateurs and Experts rode machines up to 750cc, pretty much exclusively 4-stroke twins or 500cc 4-stroke singles.
The top prospects in the Novice class often showed up with twin-cylinder Yamaha TD1 engined machines with custom frames built by companies like Trackmaster and Redline. On Ascot's super sticky 1/2 mile oval track, it really wasn't fair as the twin cylinder machines had more than a 5 horsepower advantage over single cylinder bikes from Europe.
Yamaha decided to seize this opportunity and the publicity that came out of winning races by introducing the Ascot Scrambler. The limited production model, set up for scrambles and flat-track, was a derivation of the street going YDS2 model using aluminum cylinders similar to the TD1 road racer model. Carburetors were 24mm Mikunis - larger than the 22mm units on the S2 but smaller than the 1 1/16" Amals that came standard on the TD1 and the machines were fitted with expansion chambers. Brakes were the same as the TD1 as was the frame. Naturally, all street going equipment was shed including the front fender.
Sales of this model were indeed brisk, but owners soon found out that handling was sub-par to the custom frame twins that were being raced at Ascot. Imagine a 35 horsepower machine with a peaky powerband and a short wheelbase. Production of these very unique machines went from 1962 to 1967 with very few changes. The 1965 and later model had a fiberglass racing seat which is the only way to tell the difference between the earliest models.
Ascot's have become one of the most desirable early Japanese racing machines. Unfortunately, they are very difficult to find. The Early Years of Motocross Museum found this one in London, England.

Images are property of The Early Years of Motocross Museum, ®2006