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.

Tbird
7/17/2020 10:01:47 AM

As a high-schooler in 1975 I purchased my second bike, a stock R5C. Steeped in contempt for all things Harley and Honda, I went in search of prey, rarely finding any, to my chagrin. I saved enough for K81's, a bore job, and a Bell Star. A buddy with a brand new XS360 accompanied me on my first foray to the mountains for a camping trip. The R5 became a bit sluggish up there, but I attempted no adjustments. On a beer run to the valley I engaged a CB450 in a twenty-mile jaw-clenching road race, perhaps the most foolish fun I've ever had. I was able to take him in a tight turn, but spent most of the time looking at his taillight. I came away with a sore jaw and a grudging respect for Hondas and their riders.


jdunne
7/16/2020 8:21:48 PM

Scott...Glad that you're the "proud owner" of a highly modified R5B, but I was referring to "stock" R5s vs "stock" Honda CB-350s I raced both AAMRR and ERA/WERA 1973-1982 and saw a lot of RD-350s and 400s and a very few R5s (all of which had been converted to TR-3 road racer specs for "Cafe" and "Modified Production" classes). By 1977, yes, at many meetings that I attended (Summit Point, Rockingham, Charlotte Motor Speedway...VIR closed in 1974) almost 50% of the bikes that showed up were RDs, but almost all of them were RD-400s in the Production class, not RD-350s. While I suppose that you could shift lines with the RD more readily than a CB-350, I would have to tell you that I passed more than one RD350 by changing lines mid-corner on Honda CB500 and 550 fours (with Koni shocks) by knowing that I could rely on the Honda's steady handling (particularly at a bumpy track like VIR or Summit Point) and superior lean clearance (as compared to a stock-pegged RD350). I would also note that after shifting that line, as you suggest, the RD rider still had to contend with a front-end light machine that would want to run wide as he/she applied the throttle. Apparently Yamaha was also aware of this shortcoming as when they designed the 400, they moved the engine forward in the frame to put more weight on the front wheel, which steadied up their handling. The RD-400s also had their pegs mounted differently, eliminating the under-the-mufflers peg support of the RD350 for improved lean clearance. And certainly a CB-350F is much slower than the RD 350 or 400 or your tricked- out R5...they were also slower than a CB-350 twin! I would note; however, that I saw CB-400Fs during 1975-76 that consistently placed in the top five in ERA/WERA Production and Modified Production classes and saw 1978 CB-500T Hawks win the Production class against the vaunted Yamahas. I would also note that Peter Egan, a writer for "Cycle" magazine, won his AFM class in California with a 1978 CB-400T Hawk before he became employed by "Cycle." As for your comment that "...R5s handle like the GP racers they are directly derived from," one of the most successful Yamaha 350 racers of the time, the Don Vesco-tuned TR ridden by Kel Carruthers, had its engine moved forward in the frame to put more weight on the front wheel. Most of the other Yamaha racers of the day had similarly relocated engines. Back in those days, a bike didn't really handle on a racetrack without both wheels in firm contact with terra firma, particularly in a corner. In fact, even today's MotoGP bikes keep both wheels on the ground in corners... mid-corner wheelies are not fun!! I would also note that Yamaha's real GP bikes of the era, the RD-56 and RD05A, were hardly paragons of good handling. In fact, Mike Hailwood beat them regularly on less powerful, but steadier handling Hondas.


jdunne
7/16/2020 8:12:45 PM

Rhip ...I knew two other R5B owners in college. One, a stocker, was slightly quicker than mine until I put a K&N filter in my airbox and Yamaha accessory check valves in the my oil injection lines. They were then pretty much identical. The other R5B had expansion chambers on it and was a bit faster than the stockers, and even more wheelie prone. I also worked in a Yamaha shop one summer and got to ride R5Bs, R5Cs and RD-350s, so don't try to tell me about how the R5 was "all that. One of the shop's mechanics rode a CB-350 (yes...while working at a Yamaha shop!) and beat me regularly that summer. The R5C models, with the seamless "RD-style" mufflers were a little quicker and cleaner running than the R5s and R5Bs. I remember when Cycle's 350 Comparo came out (I'm an "old guy") and I based my initial thinking on their results...which were a crock of crap. Cycle World also tested the R5 and the CB-350K3 and the R5's best in the 1/4 mile was 15.46 seconds at 81.08 mph. The CB-350K4's best was 15.17 seconds at 83.87 mph. I even switched off with a buddy who had just beaten me on his Honda CB-350K2 (1970) and beat my own bike with my buddy on my R5. My bike had "no" issues...you just were racing "flower sniffers" on the Hondas. As an aside, Cycle World only got a 15.48 second, 82.19 mph 1/4 mile out of a Suzuki T-350 Rebel. And please spare me the whole "handling thing," I raced Production class bikes with AAMRR and ERA/WERA for about 9 years (1973-1982). On anything less than a perfectly paved racetrack (the complete opposite of your typical North Carolina back road), the Honda was much steadier, a lot more predictable and had competitive lean clearance. Btw... both Cycle and Cycle World got low-14s out of 5-speed CB-450s in the 1/4 mile.




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