Yamaha TZ-750 Retrospectby Jim ReedRoad Racing Technical Editor (c) 1995-1996 Motorcycle Shopper. All Rights Reserved. Daytona is here again. Sitting in my office during lunch the other day, I was thinking about my preparations for this year's AMA/CCS event while idly looking at a poster on the wall, celebrating Crosby's 1982 200 win. Then it struck me! It's been 10 years since a TZ-750 Yamaha last won Daytona. How things have changed! Introduced at Daytona in 1974, the TZ-750 overnight became the weapon to have, if you were serious about winning an AMA National Championship, let alone Daytona. No other manufacturer offered anything near it, in terms of speed, reliability and availability to the privateer rider. From 1974 to 1982, a TZ-750, either factory or privately backed, won every Daytona 200! Add to this the number of World Championships and National championships worldwide, and the TZ-750 will surely go down as one of the greatest racers of all time. A win at Daytona was the reason for the creation of the bike. By winning Daytona with a 750--as opposed to a 350 as Emde in '72 and Saarinen in '73 had done--Yamaha hoped to make inroads into the big-bike market. Unlike Honda and Kawasaki--and for that matter Suzuki--Yamaha had no bike eligible to compete in AMA events. AMA rules required 200 units of a bike to be produced before it was allowed to compete. Yamaha did have the awful 750 twin, four-stroke, street bike. Turning it into a racer was out of the question! For years, Yamaha had been manufacturing 250 and 350 production GP bikes based on year-old "works" technology, from their efforts in the World Championship. In October 1973, engineer Naito and designer Matusi were given the green light to produce a 750, AMA-legal racer. Since, unlike Kawasaki and Suzuki, they had no acceptable street bike upon which to base their racer, a radical decision was made; take their hard-won and closely-guarded knowledge for building 500cc GP bikes, and make it available to private racers, in quantities required by the AMA. When the news of what Yamaha had done got out, other manufacturers were in apocalyptic shock! The resulting bike was essentially a bored-out and mass-produced OW20 YZR 500 GP bike with reed valves. The bikes were available to dealers by December 1973, less than ninety days since it's inception. When I purchased my '74 TZ-750A from its original owner, Bill Labrie of St. Petersburg, Florida, I received the original MSO which Bill was given by Barney's Cycles, when he purchased the machine. Typed on the MSO was the purchase price: $3,600! A privateer's dream come true. My bike was one of the first delivered, and one of only three allocated to Florida. The other two going to John Long and Pat Hennen. As it turned out, it was the only one of the three that ran really well. Bill's son Billy, rode it to a 19th at the 1974 Daytona 200; 1st at Pocono and in the top-ten the rest of the season, earning Billy his expert license. The first 266 TZ-750As were actually 700s. The first full 750 began with bike #409-00367. Conversion kits were made available, so those with a 700cc could turn it into a 750cc. For 1975, an additional 111 bikes were manufactured. In 1976, forty were produced. The '75 and '76 models were designated TZ-750B and C. These bikes were virtually identical to the A model, except for improvements in clutch-plate material and gussets welded to the outside of the pipes to prevent them from cracking.
Agostini won Daytona in 1974 on the bike's first try. For 1975, Roberts and his tuner
Carruthers appeared at Daytona with a factory OW29 750. The bike was essentially a modified B
model. For the first time, the bike carried a monoshock rear suspension. The unit was similar
to the motocross shock in that it also had a bell reservoir at its swingarm end. This suspension
increased travel from 3.1 inches to 5.1. Another change was the new routing of the expansion chambers. The two center and one right-hand pipe, still went under the bike, but the left-hand pipe went up over the transmission behind the carbs, across the frame, exiting below the seat on the right side. This arrangement allowed for more ground clearance and better pipe shape, resulting in more power and greater reliability with regards to the pipe.
The flat pipes of the A, B and C models were good for no more than three 100-mile
races, before they were patched and broken beyond use. Also mag wheels were substituted in
place of the stock wire wheels. Aside from these changes Roberts OW29 was identical to the
privateer twin-shock bikes. In fact, it used the same frame with only brackets added as
required for the modifications. As we shall see, the OW31 was a very different machine in terms of its frame and running gear. It is obvious however that this bike was the direct forerunner of the OW31. At Daytona, Yamaha showed up with four new 750s. Aside from the engines, which were visually the same as those in the production bikes, these new bikes were 40-lbs. lighter, and overall, lower and wider. Those privateers who had modified their twin-shock bikes along the lines of Roberts 1975 bike, and figured they would be competitive with the factory, had a collective heart attack. In practice the bikes were 10 to 25 mph faster than anything else. Because of the lighter weight and lower stand, they were much easier to handle around corners, as long as the wick was turned up judiciously upon exit. The bikes were exotic, to say the least. Titanium was used for all fasteners, axles, fairing stays, chain adjusters, brake caliper pistons and anywhere else you could think of, all this in an effort to trim weight. The lower triple-tree and additional engine castings were made of magnesium. The steering-stem and brake calipers were made from aluminum, not steel and cast iron as on the earlier bike. The monoshock unit was constructed from 26mm-diameter tubing, not the 24.5mm tubing used on the TZ-750A, B and C. Finally, the engines were carefully assembled according to specs set down by Kell Carruthers. These four bikes, plus a fifth, were originally intended to compete in the 1976 running of the Formula 750 World Championship. With Yamaha's withdrawal from GP racing in 1976, the bikes had nowhere, but Daytona, to compete on an international level. The Yamaha factory entered one of the bikes for Hideo Kanaya to contest Daytona. The remainder of the bikes were loaned or sold to the following teams: Yamaha International with Roberts; Yamaha Motor Canada with Baker; Venemotos with Cecotto and the fifth for Agostini's use if he desired. Cecotto won the race after a ferocious battle with Roberts, and in the process, literally left everyone in the dust. The other factories were devastated and the privateers were yelling for copies.
For 1971, Yamaha was back with the factory OW310s. For Suzuki and Kawasaki that was bad
enough, but to top it off, Yamaha had built an additional 70 "replicas" to be sold to the top
privateers. The OW310 replicas --designated OW31--were very close copies of the factory racer.
They differed from the factory bikes in that they used no titanium and less magnesium
components. They also differed in that the standard production engine provided motive power,
rolling on wire wheels, not Morris mags. 1978 marked the end of development of the TZ-750, due mainly to the end of the 750 class in World Championship GP racing, effective at the end of the season. Production ceased with the TZ-750E, although additional bikes were assembled from spares in 1979 and sold as F-models. Between 1977 and 1979, 162 OW31 replicas were built starting with serial No. 409-200101 and ending with No. 409-200262. The last bike Yamaha USA had on hand to sell, was sold on January 20, 1983 and delivered to an individual in Europe. From the figures I received from Kenny Clark, head of the Yamaha Racing Department at Yamaha International, it appears 527 TZ-750s were built by the factory. This of course does not take into account unnumbered frames and engine cases which may have been sold across the parts counter. I consider myself lucky to have owned a TZ-750, and foolish to have sold it. Fortunately Scott Guthrie of Bonneville motorcycle-record fame bought the bike, so it's in good hands. I was also lucky to have raced, or should I say, have ridden the bike at Daytona several times. WFO on the banks at Daytona on a TZ-750. Awe inspiring! Surely, today super bikes handle better, stop harder and are just plain-better race bikes. However, I have yet to witness a Superbike 200 that compares to the experience of seeing a master such as Roberts, Cecotto or Baker, rocket around the banks approaching 190 mph. If you missed the nine-year reign of the TZ-750 at Daytona, you missed something very special in the history of motorcycle racing. Something not likely to come our way again. Jim Reed served as Motorcycle Shopper's Road Racing Technical Editor. He's written several articles for the magazine as well as other publications. — Copyright — |