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Yamaha's TZ750:
Where Legends Began ...
Kel Carruthers recalls the early days of the TZ700
by evan williams

The mighty Yamaha TZ750 was one of the legendary race machines of the 1970s, winning races for nearly a full decade -- including the Daytona 200, which it won nine times in a row. 

The TZ700/750s's first win was Daytona in 1974 with Giacamo Agostini -- Ago to his pals -- at the helm. Ago came from the pole, raced with Roberts and company for a while, and was gone. 

The TZ750's last win was at Pocono 1983 with Gregg Smrz bringing the aging machine home that day. Doug Brauneck and Miles Baldwin made it an all-Yamaha podium. The TZ was the dominant machine in AMA racing for years, but faced stiff competiton at times from Kawasaki, Suzuki and was replaced as the class standard in AMA F-1 racing by the Honda RS500.

But, while the coals were hot ...

The winning was not limited to just factory riders, almost anyone with enough cold hard cash could buy the TZ750 from a Yamaha dealer. In total, Yamaha sold nearly 600 of the machines, and many more were constructed from spares.

With all that success, one might think it was easy for Yamaha. It certainly didn't begin that way...

Although it initially displaced 700cc, the machine was called the TZ750 because it had been designed for the Formula 750 class in Europe. The FIM had banned it before the TZ ever turned a wheel, but the machine remained AMA-legal. 


image by the guy whose name dean can't remember

TZ pilots Kenny Roberts (2) and Skip Aksland try to control their 140 horsepower beasts during a mid-1970s AMA national at Laguna Seca.

The spec sheet tells the tale: the TZ700/750 was an in-line four two-stroke, with reed valve induction and a fragile dry clutch. Simply put, Yamaha's design department grafted two detuned 350 cc race engines together and came up with a somewhat conservative design that put out 90 horsepower. That was more than enough to shred every race tire of the day. The bore/stroke ratio was 64mm x 54mm.

1969 250 world champ and 2000 Chaparral Suzuki crewchief, Kel Carruthers, recalls the introduction of the TZ700, way back in 1973 when he tested the machine in Japan. 

"When I first rode it in Japan I was a little disappointed in it," recalls Kel. 

"I was Yamaha's number one rider at the time, and I went over there to test it. So I flew over and got ready to ride the bike at a test track. They said, 'Kel-san, the bike is good except for one small problem'. Well, the problem was the thing used to just shake it's head at any speed over 160 miles per hour.  Incredible tankslappers! I mean it was scary..."

"Another rider went with me, and after a couple of laps he came in and refused to ride it any more," recalled Carruthers. "The Japanese said, 'Kel-san, now it's your turn. You try'. 

"Being the young idiot I was, and being Yamaha's number one rider at the time, I went out and did some more testing."

Kel's knowledge of motorcycles that later benefited Kenny Roberts and Eddie Lawson win World Championships also helped tame the TZ. He says, "Basically it was too short. We went back to the factory that night, cut through the swingarm, added a couple of inches and lengthened the wheelbase. 95% of the problem was gone right there, then we played with the suspension a bit and got it pretty good."

The TZ remained a brutal dance partner to the unsuspecting rider, however.

"Everything on it was just too flimsy," confides the 1969 world champ. "The first time we tested over here, at Ontario, we had Kenny, Gene Romero and Donnie Castro on the bike. I can't remember what lap times Kenny was turning, but Castro and Romero were like eight seconds slower. Basically, they couldn't ride the bike. It scared them because it wouldn't handle like they wanted it."

"I had just retired to run the race team, but I got on it to do about five laps to see what the problem was. I was about a second and a half off of Kenny's times. I just piddled around the corners and held it wide open around the banking. They were fighting it all the way around the track instead of letting it do its thing. The bike was very flimsy because it had these little-bitty baby fork tubes and chassis."

Carruthers thought the initial version could have been even better. "It wasn't as fast as it could have been. They were really conservative in the way they built it. After about three or four races, we had another twenty horsepower. 

"Then the chassis really started to flex," laughed Kel.

And so the legend began.

Ends

Compare: 
the 1974 TZ700 and the 2000 R7 Superbike
TZ700 R7
Wheelbase 56.28" 56" 
Weight 345 lbs 356 lbs 
Front Tire  3.25 x 18 3.5 x 17
Rear Tire 3.5 x 18 6 x 17
Horsepower 145 173

 
 

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