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1967 Yamaha 350 Grand Prix YR1 - 4-Page Vintage Motorcycle Road Test Article
Original, vintage magazine article.Page Size: Approx. 8\" x 11\" (21 cm x 27 cm) each pageCondition: Good
The big race among Japanese motorcycle manufac-turers as to who would have a quality 350cc machinein the U.S. has finally been won by Yamaha. Factorydesignation is YR1, but to Americans the name GrandPrix will undoubtedly become more meaningful and easyto remember. Obviously Yamaha in its heritage, the GrandPrix reaches a new level in attractive styling. The generalappearance is similar to the now popular lOOcc twin in-troduced last year; in fact, public reaction has encouragedYamaha to pattern two 1967 machines along these lines.The gas tank has a slight decrease in capacity, aboutone-half gallon less, but what it does for good looks ingeneral makes up for this minor sacrifice. Also, the sidepanels housing such things as the oil tank, tool box andair cleaner are faired to match the gas tank styling.These, however, are all sheet metal changes and, whileexpensive to bring about, do not affect the total motor-cycle as much as engine modifications. It is in the enginethat the Grand Prix is really different from any Yamahasseen previously. Immediately obvious is the square shapeof the new cylinder finning. Closer inspection will reveala large circular hump on the rear of the primary drivecover. This hump is to allow for a gearbox mountedclutch; something very new for Yamaha.Previously, Yamaha used an engine speed clutchmounted on the crankshaft that performed well enough —even under the punishment imposed by racing — whenfitted to the TD series. There are disadvantages, though,with an engine speed clutch because of the high speed atwhich the plates are revolving. Most important to the rideris that it has a tendency to grab or snatch when trying toget underway. If the clutch is mounted on the gearboxmainshaft, it is turning at a fraction of engine speed, de-pending on primary drive ratio. In the case of the YR1,the primary drive ratio is 2.87 to 1, so if the engine isturning 2,000 rpm, the clutch is turning less than 700.At these lower speeds the clutch is much more predictablein operation, and the design engineers are faced with fewerproblems dealing with surface speeds and peripheral veloc-...13257-AL-68rta-08
