1966 Bridgestone 175 Dual Twin Motorcycle Road Test - 3-Page Vintage Article for Sale

1966 Bridgestone 175 Dual Twin Motorcycle Road Test - 3-Page Vintage Article For Sale

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1966 Bridgestone 175 Dual Twin Motorcycle Road Test - 3-Page Vintage Article:
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1966 Bridgestone 175 Dual Twin Motorcycle Road Test - 3-Page Vintage Article
Original, Vintage Magazine article.Page Size: Approx. 8" x 11" (21 cm x 28 cm) each pageCondition: Good
® BRIDGESTONE 175cc“Dual Twin"177cc ENGINE sits in cradle-type frame. Mufflers connect to exhaust pipesby a plastic coupling. Carburetors are covered by chrome housing withPhillips-head screws. Note the folding pegs and the breather (small blacktube) for carburetors.REMOVING the chrome cover exposes the left carburetor and oil pumpnext to it. Cable on oil pump connects to the hand throttle. Side-mountingof the carburetors makes for easy servicing. Oil line on pump connects tothe small tank behind the fuel shut-off.BRIDGESTONE 175cc “Dual Twin”Cycle [S©si(fl“The fastest growing name in rubber” building motorcycles?And how they do! Besides being this, Bridgestone is also Japan’sleading bicycle manufacturer. The Bridgestone Tire Co. was estab-lished in 1931 and began building motorcycles in the late 1950’s.Only in the past few years has their motorcycle name becomefamiliar to the people of the U.S. Many still say “Bridgestone?Never heard of it.” But not so through the midwest where they areone of the leading popular makes. Rockford Motors (formerlycalled Rockford Scooter Co.), Bridgestone’s U.S. distributor, islocated in Rockford, Illinois. The bike was supplied to us byMcCulloch Corp, of El Segundo, Calif., the West Coast distributor.“Dual-Twin”The name “Dual-Twin” should be more like “Triple-Twin” forthe bike has two parallel cylinders, dual carburetors and two rotaryvalves. Instead of having the piston do the work of a valve(opening and closing the intake and exhaust ports with the pistonskirt) a separate disc-shaped valve is used. Bridgestone must haverealized this and went all-out to design a lightweight bike incor-porating rotary valves. The job of designing one was simplified forthem by having already produced a 90cc single with a rotary valve.The Dual-Twin is by all specs a doubled-up 90cc Bridgestone“Sport.” Bore and stroke are the same. Many ask “why don’t alltwo-stroke manufacturers use rotary valves?”—the reason beingthat it is expensive to design and produce, which increases the over-all price of the machine. Another problem with rotary valves iswhere to place the generator and ignition contacts. These areusually on the ends of the crankshafts but this space is taken up bythe rotary valves. A unique method was used to solve this problem.The generator and the ignition contacts were combined into a one-piece unit, and placed beneath the aircleaner behind the cylinders,driven by the center section of the crankshaft. All this is worth-while because of the higher hp obtained, which results from im-proved valve timing (over the standard two-stroke method). Athird transfer port is used to get a bigger, more balanced gas chargeinto the cylinders and is located on the inside of the cylinderswhere the barrels connect to each other.Enclosed CarburetorsA novel feature of the engine is the fully-enclosed carburetors.Both are connected to a paper-element aircleaner by chrome tubeswith rubber couplings. This aircleaner provides a “cold air box” forthe carburetors to draw from. An added benefit is that this keepsout dirt and water. They are side-mounted directly to the rotaryvalves (as in many two-stroke racing machines).“Oil Injection”The Dual-Twin is the first Bridgestone model to have an oil-mixing system as a standard feature. It is called “Oil Injection” andthe pump is located next to the left side carb. The amount of oilthat the engine receives is in direct proportion to how much throttleis applied and engine revs. When the bike is new the manufacturerrecommends that additional oil should be mixed manually with thegas to insure proper break-in. We found this not to be necessary.The cylinders are alloy with the barrels chrome plated—this virtu-ally eliminates any chance of piston seizure. The oil reserve is heldin a main tank between the frame and gas tank. A small sub-tankmounted above the aircleaner has the necessary “peep-hole” forchecking the oil level within. All in all a very neat and that lever for?” is one of the questions people ask whenviewing the Dual-Twin for the first time. Located on the left side ofthe transmission case is the “Sport-Shift” lever. Leaving it in theforward position you can only use the standard four speeds. Pullingit to the back position engages it in overdrive. Effortless 65 mphcruising is a reality. The overdrive fifth gear extends the top speedof the Dual-Twin to about 80-85 mph. Thanks to the precision-made transmission (and a heel-toe shift lever) down shifting issmooth and positive. Another design feature of the transmission isthe rotary shift pattern. When stopping at a traffic light on a motor-cycle you have to shift down through all the gears to reach first.Not so with Bridgestone. First gear can be engaged directly'fromfourth by just depressing the shift lever forward twice. This actionbrings you through neutral to first gear. Many would appreciatethis in situations that call for a panic stop which leaves no time fordown-shifting. The Dual-Twin can be started in gear without goingback to neutral. Just pulling in the clutch lever does the trick...16515