1971 Bridgestone SR 100
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Today, the Bridgestone name is mostly associated with the Japanese tire manufacturer. That’s always been the company’s main business, but it had a thriving motorcycle arm through the 1960s, making some of the most sophisticated two-strokes built anywhere in the world. The best of them was the 350 cc Bridgestone 350 GTR, made from 1967-71, and any of the 9,000 made would be an excellent addition to a collection.
Bridgestone is the literal translation of the name of the owner, Soichiro Ishibashi. “Ishi” means stone, “Bashi” is bridge. The company built bicycles from 1946, powered bikes in 1949 and motorcycles from 1958 onwards. Sales to the U.S. began in 1963, through the Rockford Scooter Company of Rockford, Illinois.
The earliest offering was a fan-cooled 50 cc two-stroke, followed by others in 90 cc, 100 cc, 175 cc, 200 cc and 350 cc sizes. The motorcycle business was always just a side-project as the majority of the company’s attention remained on the tire business, but the bikes were extraordinarily well-made, using rotary valve technology brought to Suzuki by defecting East German champion Ernst Degner of MZ in 1961.
A number of small Japanese manufacturers failed in the early 1960s, like Tohatsu (which would become Hodaka in the U.S.) and Lilac (which built a shaft-drive Guzzi-style V-twin). After they failed, Bridgestone went on to hire their former employees to put together a serious amount of talent for the bike business. Their small two-stroke racers were very successful and a number of race-only bikes sold to the public.
The crown jewel of the lineup would be the Bridgestone 350 cc two-stroke twin GTR, introduced in 1967. It generated 37-40 bhp at 7,500 rpm, had a top speed of 95 mph, weighed 354 lbs and sold for about $700.
Bridgestone used 100 percent phenolic, self-lubricating disc valves instead of two-part units with metal, which would separate. The engines featured close-tolerance chrome plated aluminum cylinders and aluminum pistons, automatic oil injection, five- or six-speed transmissions, primary kick-start, high-output alternators and ignition, dual leading-shoe brakes and adjustable suspension.
Part of the problem with such a large corporation, however, was that motorcycle profits were lost in the tire division. Rumors also arose that other motorcycle manufacturers were concerned about Bridgestone’s success, and hinted that their tires might not be OEM fitment in future. An additional issue was the trend away from two-stroke engines due to increasingly tight U.S. emissions regulations. Faced with building a new factory and retooling for a completely new lineup, Brigestone ceased motorcycle production at the end of 1971.
Bridgestone then sold its tooling to a Taiwanese company that continued to produce Bridgestone spares and some small bikes of its own until it ceased production in 1975. These days, Bridgestone has an enthusiastic fan base, and a sound Bridgestone 350 GTR would be welcome at both Japanese and European bike shows as a contrarian talking piece in both camps.