Accelerating out of a curve with the two-stroke
engine revving hard, sun gleaming off the chromed tank and a high-pitched
exhaust note providing a vivid soundtrack, it’s easy to understand why
Bridgestone’s 350 GTR was widely regarded as one of the best Sixties
middleweights around. It’s also a bit sad to think that this model was the high
point for a firm that abandoned motorcycle production shortly after it was
built.
The GTR was one of the most sophisticated bikes of the Sixties, featuring a
disc-valve induction parallel twin engine as well as generally high quality
construction. Almost three decades after it was built, this immaculate GTR
impresses with its neat looks, crisp performance and reliable handling. Yet only
a few years after this bike rolled out of the factory in 1967, Bridgestone not
only ceased production of the GTR but gave up making motorcycles altogether to
concentrate on the tires for which the Japanese company is still well known.
After riding the twin, that decision seems strange, although it makes more sense
when you realize that the little two-stroke was expensive, costing as much as a
Triumph Bonneville in some markets. The GTR was good all right, but in most
people’s minds it wasn’t that good. Most motorcyclists were unconvinced about
the appeal of the relatively little-known Japanese company and its flagship
two-stroke twin, with the result that relatively small numbers of GTRs were sold before production ended in 1971.
Induction production
The most notable aspect of the GTR’s 345cc parallel twin engine was its rotary
disc-valve induction system, which allowed much more precise control of gasses
than the more simple piston-ported design being used by rival two-stroke
roadsters. Ironically, Bridgestone’s Japanese rival Suzuki had considerable
experience racing disc-valve two-strokes, but the firm’s 250cc Super Six
roadster, also a two-stroke twin, was piston-ported. Suzuki’s experience dated
back to 1961, when MZ factory racer and engineer Ernst Degner defected from East
Germany, bringing his team’s secrets with him and passing them on.
Bridgestone’s twin used a disc valve (one for each cylinder) on each end of its
crankshaft, with a 26mm Mikuni carburetor bolted outside each valve. Another
neat feature was the “piggy-back” alternator, situated above the engine rather
than at the end of the crankshaft, making the GTR unit quite slim despite its
side-mounted carbs. Peak output was normally claimed to be 37hp at 7,500rpm,
although a figure of 40hp was also quoted in some materials. (Most manufacturers
were optimistic with power and speed claims, and Bridgestone played that game
enthusiastically.)
In While heading Bridgestone's US
bicycle division, Petersen was able to express and evangelize his passions for
traditional good designs. A passion that had been fed by old world cycling
traditions from Europe and spread with the bike boom of the 1970's. But was
endangered by the marketing and flash culture surrounding the rise of the
mountain bike. Petersen was able to use Bridgestone's massive production
capacity to make inexpensive, high quality bikes that were aimed at a market
that valued long term use as well as performance. So the Bridgestone team took
the inherent advantages of the steel frame, mated them with well thought out
components and produced bikes that supported longer rides, greater comfort,
durability, everyday use and of course style without sacrificing performance.
They looked back at the Fin de Siecle bike boom and promoted the classic
aesthetics of that period. The bikes, which had always been nice now began to
look nicer, riders had the opportunity to sport Bridgestone manufactured classic
wool jerseys with nut buttoned shoulders and classic looks.
The bikes became better and better,
new designs were less flashy but better thought out than the rest of the market,
especially among major producers, which Bridgestone was. However, at some point
things began to go wrong. The Bridgestone ideology began to undermine sales.
Quiet quality will sell bikes to educated consumers but for any number of
reasons a shiny cheap bike will sell as quick. Bridgestone finally disappeared
from the American market when the rising yen made profitability impossible.
Bridgestone Motorcycle History Highlights;
1945-Bridgestone Bicycle Corporation Formed
1953-BS-21 “BAMBI” Production Begins
1963-Bridgestone Motorcycles Comes To America
1964-Bridgestone BS-90 Production Begins
1965-Bridgestone BS-50 Production Begins
1965-Bridgestone DT-175 Production Begins
1966-Bridgestone SR-Racer Production Begins
1967-Bridgestone 350 GTR Production Begins
1969 Bridgestone 100/GP & 100/TMX Production Begins
1969 Bridgestone Motorcycle Factory Production Ends
1971-Rockford Motors Cycle Production Begins
1975-Rockford Motors Cycle Production Ends
NOTE:
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to their articles being placed on Motorcycle Specs, it will be removed upon
request. Any correction or more info on these bikes will kindly be
appreciated.
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