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Bridging the Gap: 1972 Yamaha R5 350

The Yamaha R5 bridged the gap between road and track and had a lasting effect on amateur road racing in the U.S.

| March/April 2020

1972-Yamaha-R5-350 

1972 Yamaha R5 350

Engine: 347cc air-cooled 2-stroke parallel twin, 64mm x 54mm bore and stroke, 7.5:1 compression ratio, 36hp @ 7,000rpm (claimed, 1970 model)
Top speed: 100mph (claimed), 95.31mph (period test, 1970 model)
Carburetion: Two Mikuni VMSC 28mm
Transmission: 5-speed constant-mesh, left-foot shift, chain final drive
Electrics: 12v, AC generator, ignition points
Frame/wheelbase: Tubular double cradle frame/52.8in (1,341mm)
Suspension: Telescopic forks front, dual coil-over shocks rear
Brakes: 7.2in (183mm) TLS drum front, 7.2in (183mm) drum rear
Tires: 3 x 18in front, 3.5 x 18in rear
Weight (dry): 326lb (148kg)
Fuel capacity/MPG: 3.2 gal (12.1ltr)/34mpg (period test, 1970)
Price then/now: $739/$2,000-$7,000

By the late 1960s Yamaha’s production racers, the TD (250cc) and TR (350cc)  were enjoying unparalleled success on racetracks around the world. But the racers’ street bike counterparts — Yamaha’s bread and butter consumer products — were showing their age.

Compared to other contemporary middleweight models on the market, bikes like Honda’s CB350 and Kawasaki’s Avenger A7 350, Yamaha’s DS6 (250cc) and R3 (350cc) models relied on 10-year-old technology to lure customers into dealer showrooms. No surprise, sales began to lag.

1972-Yamaha-R5-350-fuel-tank



That was about to change in 1970 with the launch of two all-new models — the DS7 (250) and R5 (350). Beyond engine displacement, these new models were joined at the hip in many ways, sharing similar and updated platforms.

But when Yamaha Motor Corporation released those two models (the R5 in particular) the folks at headquarters in Hamamatsu, Japan, had no idea that the new roadsters — both powered by all-new air-cooled twin-cylinder 2-stroke engines — would have a lasting impact on amateur road racing in America. And the R5, in particular, did exactly that.

jdunne
3/12/2020 7:17:12 PM

Sure the Yamaha R-5 was a "bridge"....and I've got a bridge in Brooklyn that my family owns and that I'd like to sell! I owned and rode a 1971 R-5B (orange & white gas tank) during 1972-73, putting about 20K miles on it. While Cycle magazine had declared it the "winner" in a 1970 350cc comparison test and Yamaha claimed "race-bred" power and handling, I very quickly found out that a Honda CB-350 would outrun it, particularly if you didn't put a new set of plugs in the R-5 immediately before the run. At first I was very frustrated and bewildered about this situation, but I later came across the Cycle World tests of both bikes and learned that their CB-350 had been almost 1/2 second quicker in the 1/4 mile than the R-5 (15.1 vs 15.5 sec.). I also got the chance to ride several CB-350s (as well as other R-5s and, later, the RD-350s) and found that they were easier to get off the line than the R-5 and covered ground much faster than their engine note would otherwise indicate (the R-5 always sounded fast...it just simply wasn't as fast as it sounded). The idea that a stock R-5 would run as fast as a bike "twice its size" as indicated by many propagandists (or old owners with "rose-colored glasses) is quite simply preposterous and mythical. While an R-5 could, possibly, give a single-carb, 4-spd Triumph or BSA 500 a hard time, it would simply be an appetizer for a Triumph Daytona or CB-450 with a 5-spd box. As well, the R-5's tranny ratios didn't help as there were significant gaps between 1st and 2nd and 4th and 5th gears. One had to wind 1st gear pretty tight to avoid bogging when you shifted into 2nd (despite the R-5's relatively wide power band for a piston-port engine) and you could get caught in city traffic situations "between gears" (1st being too low, while 2nd was a bit too high). As well, 4th was useless as a passing gear above 60-65 mph (it needed the "bridge" of an RD's 6-spd gearbox). The handling was also less than stellar, being that the R-5 had too little weight on the front wheel (at least with the stock handlebars), a short wheelbase and quick steering...can you spell t-w-i-t-c-h-y? While the light front-end enabled you to pull easy (and many times unintentional) wheelies (reinforcing the illusion of speed and power), it also made the steering and handling rather dicey coming out of corners, particularly on a road with slow, tight curves (just the kind of road where you might think that you could catch that CB-450 or Triumph Daytona 500 that had just blown you away on acceleration). And like most 2-strokes of the period, points and plug life were also issues...aggravated by the fact that Yamaha didn't have any check-valves in their Autolube system (Bridgestone, Kawasaki and Suzuki all had them) which contributed to over-oiling, particularly at idle. I eventually gave the R-5 to my Dad and purchased a left-over '72 Honda CB-500 Four, riding and racing it with AAMRR and WERA for 3 years and 30k street miles and being much happier. The only "R-5" that could run with it was disqualified for having TR-3 cylinders (and may've had a 6-spd box too). I will give Yamaha credit for one thing; however, "The Sow's Ear to Silk Purse" award for converting the R-5 into the 1973 RD-350...which corrected almost all of the R-5's shortcomings (except for plug fouling)....but was really no quicker than a 1969 Kawasaki A-7 350. I will forever wish that I had bitten the bullet and bought a Bridgestone 350 GTR instead of the R-5...6-spds (no need for a "bridge"), rotary valves (more power and a wider power band), rubber-mounted engine (no vibration), more weight on the front wheel and a much better highway bike for running home from college on weekends. 'Course the CB-500 Four addressed all of those issues...plus!!


rkover
2/27/2020 2:29:55 PM

Thanks for this. My first bike was a 1972 R5C. I recently found another, currently awaiting restoration in my garage. Thanks!


Gary W.
2/27/2020 9:27:59 AM

You certainly pushed my fun-button with the RD 350 story. Like many of the day, we were mid-pack endurance-racers with an RD 250 and its huge reliability and killer power, with added pipes, or course. Like many, it never spit any of us off even when the tires were showing cord and even when we probably deserved it. I do wonder about what happened to Ivan Wagar. I recall him telling us one time about him racing a Moto Guzzi in the 1950s and why the factory purposely declined to paint their dustbin fairings of the period. Does anybody remember why that was, or what ever happened to Ivan? Thanks for the continued excellent contributions. Gary W.











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