|Racing Bikes Z750|
In 1974, Yamaha came out with its first-born 2-stroke, inline-four production road racer. The TZ700 was a 90 hp, 694cc engine that had the same 64mm bore size as the TZ350 and RD350. It had twin shock rear suspension. In 1975, cylinder bore was increased to 66.4mm yielding 747cc, producing about 15 more hp. The rear suspension was also upgraded to Monoshock.
The first version of the TZ750 was not actually 750cc, but a 700. Yamaha simply doubled up their successful TZ350cc twin to create one of the most successful racing motorcycles that dominated open class racing for a period of ten years. The next version, the "B" model was at last a full 750, obtained by increasing the bore to 66.4 mm, with peak horsepower at 105.
The Yamaha 1979 TZ750 "F" motorcycle was the last version of the TZ750, and was virtually a replica of the OW-31 factory racers. A total of five hundred and sixty seven TZ750s were produced from 1973 to 1979. The "A" version was actually a 700cc, the cylinder bores were increased to give 747cc in 1975.
Georgia pig farmer, Dale Singleton, rode this TZ to victory in the 1981 Daytona 200 Race. These big TZ's were the preferred motorcycles by the majority of racers of a span of six years until the regulations for the 750cc were changed, and specified four stroke motors only. The "F" model was the final version of the TZ750s.
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 three-cylinder 750s. 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 PalomoFIM formula 750 champion in 1976rode 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.) Cooling: Water 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
1978 Review 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 intakesall 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 reelsyou 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 racerand 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 damper.
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 taskinstalling 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 overor so he thought. 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 jobto 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 onethe 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 was 84dB(A). 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 stopped since. Source Cycle 1979