1974 Yamaha 250 Road Racer Motorcycle History - 10-Page Vintage Article For Sale

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1974 Yamaha 250 Road Racer Motorcycle History - 10-Page Vintage ArticleOriginal, Vintage Magazine Advertisement / ArticlePage Size: Approx. 8" x 11" (21 cm x 28 cm)Condition: GoodYAMAHA 250ROAD RACERHistory ot the Privateer’s Best Friend-By Kevin Cameron©In the years following World War IImany riders in England and Europelearned roadracing on single cylinderManx Norton production racers These500s and 350s were designed to be simple,maintainable, and effective. Above all,they were available. Those who didn't race30M and 40M Nortons very likely wentto starting grids on AJS 7R and G-50Matchless models. Riders on their way upwere spared the tasks of engineer, ma-chinist and financier., and were thus ableto concentrate on riding. The British sin-gles gained a reputation as rugged, well-engineered motorcycles.A similar situation exists today, but thebrand is different. Yamaha 250 productionracers have been the standard mount forbeginning roadracers for ten years now,and they have dominated international250 racing for five years. In any countryof the world where roadracing exists, youwill find most riders and tuners are thor-oughly familiar with these machines.The engines are derived from roadmodels, and al the present lime, theframes, forks, and other important partsare shared with the street-going counter-parts as well.How has this situation come about?What combination of circumstances hasled this company to produce hundreds ofbasically simple machines that win bothclub events and international races?Many companies in postwar Japan sawdiversification as a key to economic sur-vival. Cheap transportation was needed,and motorcycles were a good answer. Ya-maha made the improbable jump frompianos to motorcycles. The early machinesclosely resembled European models. If. . ./-*i »r>T 1 H7/1you have no national motorcycle industry,you gel a piece of someone else's. Bylicense agreement and exchange of engi-neers, Europe's motorcycle design tradi-tions were absorbed by the budding Japa-nese manufacturers. About 1955. such anexchange took place between Yamaha andthe German Adler firm, Germany hadbeen the birthplace of effective two-strokes with the prewar DKW machines,and had continued to lead the world intwo stroke design. The first Yamahatwo stroke twins strongly resembled theAdler. The carburetors were bolted to thecrankcases, feeding the cylinders throughslots. The clutch was crankshaft-mounted.Rivalry among the new companies inJapan was strong, and the leading raceof that time was the Mt. Asama cinder-track “roadrace.” Competing against suchnow-defunct names as Tohatsu and Me-guro. the Yamaha company was deter-mined to win this event, which took placein the shadow of Ml. Fuji.This first Asama racer was the mostdistant forerunner of the production racersof today. The first machines were madewith two different bore/stroke ratios, theP model having the dimensions 54 x54mm. and the PQ measuring 56 x 50.In 1956. Fumio Itoh succeeded in win-ning the Ml. Asama event for Yamaha,which increased the determination of themanagement to seek further successes.The Honda Motor Company could onlylook on enviously at this time, but laterthe two firms would meet in competitionon the Asama course, a foretaste of thegreat European GP struggles they wereto fight out years later.The design of the P model required thecylinder to be sunk very deeply into thecase, thus limiting fin area. The pistonsof the time were made, like car pistons,from a fairly soft, high-expansion alumi-num. These two facts made trouble forthe racer. The gearbox held only fourspeeds, creating a further limitation.Two stroke tuning in Europe was re-ceiving a powerful impetus from the EastGerman MZ firm, which was building onthe knowledge gained by DKW. Their1953 125cc racer gave a pitiful 9 bhp at7800 rpm, well below the performance ofcontemporary four strokes. In the nextfive years, they tried and discarded a fan-tastic array of strange designs, finallyemerging with what was to be the defini-tive two stroke powerplant of the future.This was the loop-scavenged, disc-valve-inlel engine, exhausting through a baffledmegaphone, or expansion chamber. The1960 version of this 125 single gave 22bhp at 11.000 rpm. for a bmep (brakemean effective pressure) of 104 psi.Yamaha kept informed of trends inEuropean design, and they too saw theadvantages of this layout. They begantheir own work with this type, and broughttheir first rotary' valve racer to Europe in1961. This 250 RD-48 model gave 35 bhpat 10,000 rpm. 94-psi bmep. The enginewas air-cooled, pump and gas/oil lubri-cated. and housed in an open-loop framemuch like that of the G-50 Matchless. Itwas no match for the championship-win-ning Honda of that year, but it addedgreatly to Yamaha's growing knowledge ofracing two strokes.While this European effort was gettingunder way. management looked into ex-porting road machines to the United...17442 RL- mb3370-7408-04