The law of unintended consequences is one which always defeats legislators throughout the world – and in whatever sphere they operate.
Gene Romero on the TZ750 at Laguna Seca.
In 1972, the AMA was becoming discomforted – and you can translate that into the vernacular to know how they were really feeling – about the way things were going in the Grand National Championship.
BSA/Triumph had started the serious rot by turning up with factory bikes which, except for a few engine castings, were full on factory racers. Not that Honda was any less guilty with its CB750 race kits which transformed a refined, but sedate, 750cc racer into a full on GP bike.
To the AMA, the answer was simple and obvious. Introduce a straightforward rule which said that if a bike was going to be raced in the National Championship there had to be 200 examples made. Now, the playing field would be completely level once more and, most importantly, Harley-Davidson would be able to re-join the major league.
In this golden period for American motorcycle sport the one race to win in the American calendar was Daytona and initially, Yamaha was at a huge disadvantage at the Florida race track. This was only ameliorated by the tri oval’s tire-shredding, high-speed banking. Suzuki and Kawasaki both had large capacity two-strokes which readily converted to race machines to meet the new regulations – but these bikes simply destroyed tires.
Not having a large capacity two-stroke in its road bike range, Yamaha could only field its 350cc twin-cylinder racer but this was good enough to win the “200” in 1972 and 1973. However, the writing was well and truly on the wall. When the tire problem was solved then the game would be up for 350s at Daytona.
What the AMA didn’t reckon with was a manufacturer actually mass producing a GP bike but this is precisely what Yamaha did with the TZ750. This would be no converted road bike but a full on race machine from front wheel to back.
To understand Yamaha’s decision, we have to go a fair way back into the history of motorcycle racing. In the heady days of Yamaha’s world-wide expansion, its flagship bikes were always twin-cylinder two-strokes. Yamaha’s management always liked to link racing very directly to its road machines and so right from the TD1 in 1962, they sold twin-cylinder race bikes which the well-connected privateer could purchase. These were true over-the-counter racers and you simply put gas in the tank and headed for the track.
In another example of the law of unintended consequences, the FIM decided to simplify racing in 1967 by limiting all 250cc racers to only two cylinders and six speeds. The effect was immediate and dramatic. Instead of exotic six-cylinder Hondas and four-cylinder Yamahas and Suzukis the class became as dull as the CEO’s speech at the office Christmas party with every bike sounding and looking the same.
Clearly, spectator attendance plummeted and GP road racing fell into a trough.
Factory interest was minimal too and this allowed some really odd things to happen. Ex-Yamaha works rider Phil Read took a completely standard, but tuned, 1971 Yamaha engine to British motocross frame builder Eric Cheney, with the instruction to make a chassis which handled.
Eric had never built a road racing frame before but didn’t think that the job was too difficult and set to with his artist’s eye, a tube bender and a welding torch. Three days later, the Cheney chassis was finished and it was good enough for Read to win the 1971 World Championship.
As well as the 250cc Twins Yamaha also made some lovely 350cc Twins and these too were freely available to well-heeled privateers.
When Yamaha decided that it would start taking racing seriously again, it did so with a 500cc, four-cylinder bike which was built for the “Flying Finn” Jarno Sarineen.
Tragically, Jarno was killed at Monza in 1973 and this was an immense blow to Yamaha which had really taken the charismatic Finn to their corporate heart.
However, before he died Jarno had won two 500cc GPs on the OW20. The inspiration for the 500cc Four came from Yamaha’s GL750 road bike – an across the frame, four-cylinder two-stroke which was displayed at the Tokyo and Paris shows but never made it into production.
) The instrumentation is basic on the TZ750. (Below
) A fabulous name on the fairing of this TZ750.
The engine of the OW20 was both simple and elegant. It was not, as is now widely reported, a pair of Yamaha’s existing 250cc Twins linked together but was very much a new design – although drawing heavily on the experience the factory had with Twins.
The Twins were linked together with a central gear – an idea that had been around for decades. This gave a 500cc four-cylinder bike with a lot of power.
To address the problem of 80 horsepower spinning the rear wheel when the power kicked in, Yamaha took the reed valve technology from its world championship motocross experience. The reed valves enabled much bigger bore carburetors to be used than in a conventional engine and also softened the power delivery.
If a pair of 250s could be harnessed together to make a 500, then why not up the game with two 350s? There wasn’t a reason why not and Yamaha had a further incentive in the arrival of one of the world’s greatest motorcycle racers in the form of Giacomo Agostini.
Ago desperately needed a big bike for Formula 750 races – and Yamaha needed to win Daytona which, in the early 1970s, was considered to be one of the most important international races in the calendar.
Ago came directly from MV Agusta where small, neat and light were considered to be the three paths to greatness. Like many riders before and since, Giacomo asked for what he knew best and specified a 53.5 inch wheelbase. A bike like this – 1.5 inch shorter than a Manx Norton or Matchless G.50 – turned on a dime but was more than incredibly frisky in a straight line.
Initial tests of the new bike – code named OW19 – were not encouraging. The Japanese test riders got off the bike in a state of shock and with no desire to continue riding it. Yamaha’s savior turned out to be Australian Kel Carruthers – one of the most intelligent and perceptive riders of his generation.
Kel was not only a very fine racer, and a World Champion, but he had also ridden some of the best handling bikes of the era in the form of Manx Nortons and Aermacchis. He looked at the big Yam in horror and immediately asked for the swinging arm to be extended by three inches.
Carruthers remembers the test clearly: “Well, the problem was the thing used to just shake its head at any speed over 160 mph. Incredible tankslappers! I mean it was scary...
“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 core of the problem was that the OW19, now officially called the TZ750, made superbike power but was still very much a classic chassis. Disc brakes apart, a rider from 1955 would have looked at the Yamaha and found it familiar. For example, the tiny swinging arm was constructed from two thin steel pressings welded together and the frame was an equally light construction. This would have been fine for 50 hp – but when over 90 hp was being put through it things were very different.
Regardless of the bike’s shortcomings, Giacomo earned his considerable salary by winning the 1974 Daytona 200 and the TZ750 took its first steps to fame.
Not that things were straightforward. The TZ followed standard Yamaha thinking by having its four exhaust pipes running underneath the engine. This was fine on the Twins, where the pipes were widely separated, but was a disaster with the four-cylinder engines packing four pipes in a space suitable for two.
The front forks are flimsy for 175 mph.
At 10,500 rpm, the exhaust pulses caused flexing in the expansion chambers and Agostini was very lucky to make it to the finish of Daytona.
It wasn’t a happy place in terms of handling either. As the 1974 season progressed, it was found that the retaining clips securing the front fork dampers could pop out, leaving the already flimsy forks with no damping at all. At this point, many owners of the $3600 TZ750 decided that they would be much better off on a 350 which had vice free, Grand Prix quality handling – rather than a desire to kill its rider.
Over the winter of 1974/75 Yamaha took the TZ from 694cc to a full 747cc and this is where the bike which features in this story comes into its own.
This TZ was originally allocated to Kenny Roberts and then came into the hands of Gene Romero. I must confess to being a Romero fan. As a baby journalist, I worked with Gene on a number of occasions and, at a time when riders were not PR trained or aware, Romero was kind, courteous and the complete professional. He was also a much, much better rider than he was sometimes given credit for and could have been a serious challenger for the 500cc World Championship.
In those days, qualifying for Daytona was a flat out lap of the 2.5 mile, steeply banked oval. It was a daunting task as Barry Sheene proved when his Dunlop tire gave up at 175 mph and he undertook the most famous high-side in motorcycle racing history.
Gene and the Yamaha were doing over 175 mph lap after lap and this was a seriously dangerous exercise.
Romero was, and is, a thoughtful racer and his race plan was, in his own words, “…to let the hot dogs wear themselves out.”
And there was a fine collection of the hottest of dogs in the form Kenny Roberts, Romero’s teammate in the Yamaha factory squad but riding the later and better handling Monoshock TZ; Giacomo Agostini on another factory Yamaha; Steve Baker; Steve McLaughlin and GP star Tepi Länsivuori . Every single one was a strong contender for a win.
Once Roberts got down to work he opened up a 15 second lead over Länsivuori until his clutch expired.
Länsivuori’s race ended when he dropped his Suzuki and the drama wasn’t over for Gene either. On lap 27, the TZ seized. Gene said: “I thought it was all over. I pulled in the clutch, coasted 50 yards and was ready to pull it onto the infield and park the bike when I decided to give it one more try.
“Everything seemed to work okay so I kept on going, but for the rest of the race I rode with two fingers on the clutch.”
Gene took the checkered flag, leading an astonishing 19 Yamahas home in the first 20 places. Truly, the TZ owned Daytona.
The TZ then passed through numerous hands, being raced in Britain and Ireland, but all the time with its history known.
Now, British auctioneers H&H are offering it for sale at their Imperial War Museum auction on April 24. The estimate for the bike is a serious $75,000 to $82,500 and then there is the 12% buyer’s premium on top of this. This will make the bike an $85,000 - $90,000 purchase which just goes to show the power of provenance and history when it comes to these exotic race machines.
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