Yamaha TZ 750
The official Yamaha 350 racer, Jarno Saarinen, rode to victory
in the 1973 Imola 200 Miles after having won that year's Daytona 200. It was at
the Imola race that motorcycle fans first got word of the four-cylinder Yamaha
700, a new speed demon that had been built by the most famous manufacturer of
international racing motorcycles to challenge the Suzuki and Kawasaki
Saarinen was responsible for the publicity leak, although it was not all that
indiscreet. The new Yamaha engine consisted of two 350-cc. racing engines put
together. In tests it generated 140 h.p.
The Yamaha 700 was tested secretly on the company's own track.
Giacomo Agostini, who had joined the team, tried it out first after the test
driver Hideo Kanaya had tuned it. Agostini had switched to Yamaha chiefly to
race formula 750 in the
United States. He rode the new 700 to win the 1974 Daytona 200 Miles and the
Imola 200, sister race of the Daytona. From that moment on, the 750 class
throughout the world was the exclusive property of official and private riders
of the Yamaha, except for occasional sorties by Kawasaki and Suzuki.
At first the four-cylinder 700 had an engine built by putting
together a pair of two-cylinder Yamaha 350s with gill-port distribution. The
engine generated some 115 h.p., making possible a top speed of about 185 m.p.h.
The chassis had the classic double cradle with traditional suspension.
Altogether the motorcycle weighed over 350 pounds, which was too much for a
racing motorcycle. Agostini tried out an interesting chassis modification in
order to improve the vehicle's maneuverability and stability.
A rear suspension with triangulated Yamaha 700 Four-cylinder
swinging fork was installed. The upper arm worked the single central shock
absorber, which was mounted in a semihorizontal position under the fuel tank.
The new type of suspension, called "monocross" or "cantilever," was installed on
all subsequent Yamaha racers. In 1975 the TZ 700 became the TZ 750. It was not a
question of merely increasing displacement, but involved an overhaul of both the
engine and the chassis. The Yamaha Daytona had always looked bulky and clumsy,
but after this overhauling it looked sleek and powerful.
The Yamaha TZ 750 was unbeatable in formula 750 racing. Suzuki and Kawasaki
turned out new models without being able to overtake it.
Until the end of the 1976 season, Cecotto, Roberts, Romero, Agostini, and Victor
Palomo—FIM formula 750 champion in 1976—rode official, private, or
partially-assisted Yamaha TZ 750s. Thanks chiefly to its mechanical robustness
and its 140 h.p., this motorcycle dominated the major speed races.
Motorcycle: Yamaha TZ 750 (model OW 31, official 1976 version) Manufacturer:
Yamaha Motor Co. Ltd.,
Type: Daytona and FIM formula 750 Year: 1976
Engine: Yamaha four-cylinder in-line, two-stroke, with cross-port distribution.
Displacement 750 cc. (66 mm. x54 mm.)
Transmission: Six-speed block
Power: About 140 h.p. at 10,700 r.p.m.
Maximum speed: Over 185 m.p.h.
Chassis: Double cradle, continuous, tubular. Front, telescopic fork suspension;
rear, cantilever telescopic suspension
Brakes: Front, double hydraulic disk; rear, single hydraulic disk
Close your eyes for a moment and try to visualize
the ultimate café racer. What do you see? A tricked-our RD400? Not enough motor.
Think bigger. What do you see now? A reworked Kawasaki 1000? Not enough
handling. Try again, and think exotic. You see a Ducati Desmo 900? Not exotic
enough, and too slow. Close your eyes again. Picture Kenny Roberts in 1974.
Picture Kenny Roberts road racing. Now picture that kind of bike with a
California license plate. What? A street legal TZ750? Totally outrageous? Yes.
Sifting on a side street, you familiarize
yourself with the TZ's controls. You remember that the shifting pattern has been
converted to one-up, four-down. Across the Molly-striped tank, the clip-ons are
fitted with the standard controls as well as an added mirror and light switches.
The K&N filters on the outboard carbs crowd your knee-space, but thankfully they
are somewhat flexible. Instrumentation consists of a water temperature gauge and
a tachometer red-lined at 10,500.
You flip on the ignition, check the petcock and
get a push. Easing out the clutch, the engine springs to life. Instantly you are
assaulted by mechanical noise: straight-cut gears, dry clutch and hissing
intakes—all funneled up by the fairing. You almost have to listen for the
muffled exhaust note, but the unmistakable tone of a racing Yamaha four-cylinder
is there. Blipping the throttle, the engine revs freely with no sign of
hesitation. The clutch isn't grabby at all. More surprising is the amount of
low-end torque available. The bike feels like a strong 500 and isn't the least
bit fussy. Sifting at a stoplight the bike idles like your garden variety street
bike. But looking down, you see a yellow TZ750. Your mind reels—you should be
gridding on a race track, not waiting to merge onto a freeway.
Into traffic, and the bike rolls merrily along,
content to go with the flow. The road clears up ahead, so you dial up some
power. The tach hits eight and rockets to 12,500. Your heart stops at TDC. It's
like being launched from an aircraft carrier. The front wheel begins to skip off
the asphalt, spending equal time in the air. You're in trouble. The cars around
you that were doing 55 mph seem to have suddenly stopped and parked. Those cars
that were ahead, out of sight, are suddenly right here, and you haul down on all
three discs. Off the main road and into the curves, and the TZ is ready. Heeling
over, nothing scrapes. Braking is strong but smooth, progressive and fade-free.
The bike does all you ask of it, and then some. Why not? It is, after all, a
road racer—and it's much better at going fast than you are.
Putting a road racer on the street isn't quite as
impossible a task as one might think. It doesn't require any political
connections, bribes or even much money. But it does require a fantastic amount
of patience. Joe Taormina had sufficient patience to complete the task, as well
as a little help from his friends. The fact that Taormina is a mechanic at
Yamaha of Pacific Beach, near San Diego, also helped. The manager, Bob
Schaeffer, was quick to provide Joe with access to the shop on Sundays. Service
manager 011ie Olivera and fellow mechanic Tom Zaragoza provided Joe with
suggestions, advice and helping hands whenever needed. This sense of voluntary
teamwork was typical of the project in general. Friends, acquaintances and
customers alike were drawn toward the project, always willing to be of service.
The creation of the street-legal TZ750 began as
the typical quest for "something different." Taormina had been considering
construction of a street-legal flat-tracker. Then he read an article in which
Don Vesco alluded to the fact that someday he expected to see someone ride up on
a TZ750. For Taormina, that was enough.
Searching in the San Diego area soon yielded a
somewhat thrashed TZ750 whose owner was retiring from racing. The price of $2900
was reasonable, but
Taormina needed help. Banks and loan institutions
weren't receptive; for some peculiar reason, they considered building a café
racer untenable grounds for a loan. Undaunted, Taormina altered his premise for
a loan to read as "funding for a research project for an experimental
motorcycle." One banker finally accepted this line of reasoning, and Taormina
was the new owner of a used TZ750.
Stripping down the bike revealed the TZ to be in
better condition than it appeared. Coolant had been leaking into the
transmission, but this proved to be only a minor problem. A tube which routed
water through the gearbox had been kinked and cracked. Replacement of seals and
this tube constituted all of the necessary repairs. The transmission looked as
good as new. Even the clutch plates and piston dimensions were within acceptable
limits. The painstaking task of assembly could not ignore the State of
California. The list of street-legal requirements set forth by the Department of
Motor Vehicles in- cluded: an electrical system, complete with a battery and
charging system; a brake light which would operate with a dead engine; turn
signals; mirror; and horn. A headlight was not required but included in the
plans. Taormina wanted to keep the TZ as close to its stock appearance as
possible. Having seen too many other specials and custom bikes cluttered up with
poor detailing, he was determined to make his modifications as unobtrusive as
possible. To do it right would take a lot of time.
As Taormina worked in the shop on customers
bikes, he would develop mental pictures of alternatives for fitting in the extra
parts. By picking up ideas here and there, trying some, keeping a few and
discarding most of them, the bike began to come together. The biggest obstacle
was locating a lighting system. The wiring harness from a DT 400 looked like it
would work perfectly, but its tight-fitting CDI unit couldn't handle the
12,000-rpm engine speeds and would produce too much flywheel effect. The R5 350
alternator system wouldn't work without modifying the side case. Finally, a call
to Weda instruments in Aurora, Oregon produced results. Known primarily for
their off-road lighting kits, they were willing to tackle Taorrnina's lighting
dilemma. The cornpany was able to develop a unit which worked off the existing
T7 unit. By tapping the source coils in the CDI, the solid-state unit would
charge a 12-volt battery at the rate of one amphour, without affecting the
ignition system. The small Weda unit was easily hidden away and the battery was
tucked in under the tail section. The stock DT 400 key switch was discretely
situated under the seat, while a stock set of Yamaha switches provided
finger-tip accessibility. Fitting the light switches on the short clip-on
handlebars required relocating the choke lever by attaching it to the steering
While the electrical system was being
straightened out, Taormina stripped the frame, added tabs for the sidestand,
etc., and then repainted the chassis. The tank, fairing and tail section were in
serviceable condition but in need of a new coat of paint. Dave Harris, a former
customer, volunteered to undertake the task. Harris had given up flattracking
and was going back to school. He was, however, still doing painting in his
garage. They chose to model the bike after Kenny Roberts' 1974-1975 racer.
Harris' execution was flawless; the bike turned out to be a virtual replica.
Installing the glasswork, lighting, horn and
mirror left only one major task—installing mufflers. Taormina chose Supertrapp
silencers from Discojet. These silencers can be tuned for backpressure and/or
loudness by adding or removing plated discs. Stacking more discs increases
loudness while relieving back pressure, while removing discs does the opposite.
Martin Specialties in nearby Spring Valley cut and welded the pipes and mufflers
to achieve the appearance Taormina desired, while maintaining the Ground Clearance and strength necessary. After repositioning the four mufflers
innumerable times, they arrived at the correct combination. Once together and
running, the only modification necessary was the replacement of the carburetor
slides. Taormina replaced the racing slides with standard Mikuni slides. He
drilled and tapped holes for idle screws on the four carb bodies, and he now had
a TZ750 that would be streetable and street-legal. The hard part was over—or so
Taking the bike down to the Department of Motor
Vehicles, Taormina began a series of confrontations with the bureaucracy of the
State of California. The person behind the registration counter at the D.M.V.
listened to Taormina's proposal. Sorry, he was told, but the Yamaha TZ750B was a
racing machine and was on the list of motorcycles deemed "unlicensable." He
pointed out that his TZ was a TZ750A model, not a "B" model. After much
discussion with the person in charge, the D.M.V. countered that ploy with one of
their own: they added the TZ750A to their "black list." Attempting another line
of attack, Taormina asked them what he had to do to make it legal. If he had
constructed a trailer from scratch, for example, he could just follow D.M.V.
guidelines to make it legal and license it. Why couldn't he just do that with
the TZ? After extended hemming and hawing, the D.M.V. people did the logical
thing and passed the buck. They said it was up to "Sacramento."
Calling up the main office in Sacramento produced
more excuses. They couldn't explain why not; they just knew he couldn't. They
gave no logical or rational argument; just a flat no. Being the patient sort,
Taormina countered again with the suggestion that if the TZ was up to acceptable
specifications, he should be able to operate it on public roads. The D.M.V.
people, with no logical course of action, carried through with their form of
logic and passed the buck again. They agreed, with no lack of snickering and
eye-rolling, that if the California Highway Patrol would certify that the TZ was
indeed up to Vehicle Code specifications, they would license it. Their
understanding, of course, was that the CHP would reject the bike and settle the
matter once and for all. On his way out, Taormina vowed to himself that he would
be back to beat them at their own game. After three weeks of phoning the CHP,
Taormina arranged for a vehicle inspection. The inspection would take place in
the San Diego Stadium parking lot and would include tests with a sound-level meter.
The morning of the test, Taormina arrived at the
stadium to find four patrolmen present, bristling with code books. Their
attitudes ranged from interested and sympathetic to hard-nosed and antagonistic.
However, they were all there to do their job—to make sure the TZ met all
regulations. First, they checked all bulbs and the taillight to insure they
carried the approved D.O.T. numbers. They were all legal. Next, they examined
the electrical system. Battery? Located under the tail section. Charging system?
Taormina produced schematic diagrams and offered to take voltage readings. The
electrics were approved, as were horn, mirror and signals. The TZ had passed all
tests, save one—the sound test.
The test requires that a motorcycle be operated
at 80 per cent throttle in second gear as it passes the sound-level meter. The
meter is located 50 feet away from the motorcycle's path, at a 90-degree angle
to the direction of travel. As Taormina made his first pass, an officer
signalled him to down-shift. Due to the TZ's high gearing, they assumed that he
was in too high of a gear. Assured that he was in second gear, Taormina made
another pass. The reading was 106dB(A). Sorry, he was told, but the legal limit
Disappointed but undaunted, Taormina began
working on the bike. Contacting Discojet, he explained his problem. They
suggested using their "quiet core" kit and reducing the number of plates in the
muffler. After making these modifications, he arranged for another test date.
Meanwhile, he had borrowed a $300 industrial sound-level meter, which was used
for meeting OSHA sound regulations. Taking his own sound readings, Taormina had
recorded his TZ at 82dB(A).
At the second test, Taormina brought along
friends to take sound readings and to check what the CHP meter was reading.
Making his second gear pass, the borrowed meter read 82dB(A), but the CHP meter
read 92dB(A). Sorry, the officers said, they had to go by their own meter.
Failing the second time only made Taormina that
much more determined to pass the sound test. This time he took all but one plate
out of the muffler. He wrapped the pipes in asbestos. He built a foam-lined air
box to muffle intake noise. He mounted the fairing to shield the engine noise.
He was ready to try again.
The third test proved to be worse. His
modifications actually made the motorcycle louder by redirecting the noise.
After three tests and nine weeks of work, it seemed that it would be impossible
to pass the noise tests. The TZ was a racing bike indeed, and it just made too
much mechanical noise to pass. Taormina took his final recourse. He stuffed the
pipes. With fiberglass restricting the exhaust pipes, the engine wouldn't rev
past 6000 rpm, but it was quiet enough to pass at 86dB(A). One CHP officer
pointed out that 84dB(A) was all that was necessary since the bike was a 1974
motorcycle and therefore subject only to 1974 regulations. The bike was
certified. Before departing, the one officer who was the most zealous of the
group took Taormina aside. The officer reminded him that the motorcycle had to
be kept in this exact form; if one thing was changed, it would be in violation
of the state vehicle code and be subject to citation. Taormina replied that he
realized this and thanked him for the reminder.
On the way home, Taormina stopped by the DMV for
licensing. It was, to say the least, .an eminently satisfying experience. With
his temporary license in hand, he went home and did what any red-blooded,
all-American citizen and café rider would do. He unstuffed the pipes, removed
all the excess sound insulation and signals and went riding. He hasn't been
Source Cycle 1979