It's Alive! Dr. Sean Dwyer transforms ex-works TZ750 into a one-off monster.
Bethesda, Maryland ~ Dr. Sean Dwyer has raced BSAs, big Wood-Rotax singles and Yamaha TZ350s. He currently street rides an R90S Beemer, and a Vincent Black Knight.
In the remaining interstices of life, he's managed to rebuild one of the all time great works-based specials.
It's early fall, a lazy Sunday in a wooded neighborhood in the suburbs of Washington, DC. Suddenly, the peace is rent by an otherworldly shriek. Moments before, cardiologist Sean Dwyer had broomed aside marble-like acorns from his sloping driveway and bumped started his TZ750 Yamaha, an ex-"works" bike turned "naked" special. He's blipping the throttle gently because even indulgent neighbors have their limits! The jaunt to follow will continue the bike's running-in process. Only not here.
At a turnout beside a road less traveled, we roll the bike down the ramp and Dwyer mixes the two-stroke's special 16:1 gas-oil elixir. I push him off and with a sound totally unrelated to an old RD 350's he's off the shady turnout and gone.
After a period spent blitzing traffic up and down the road like a man possessed, the normally dour doc pulls up all smiles and grins. Had the new "friendlier" gearing helped? Indeed! "Didja' see the front wheel come up? The front was shaking & I think I need a steering damper!" We managed a few snaps in our time in public, but were almost shut down by a stone-faced US Park Policeman. "Visitors want peace, not smoke and excitement." Sure, but the tree pruners with their chain saws were just as loud and.... (Shut up, Walsh!) By a hair's breadth we avoided an impounded bike - or worse.
"I'd raced TZ350s for a number of years," Dwyer goes on, "so I sorta' had the 'TZ Disease.' "
Back from our "action shoot," we give the still-toasty four-cylinder racer a once-over. It's tiny, save for the giant engine in the Spondon frame. With few nods to fashion or legality (pip-squeak horn, prop stand, simple lighting), the racetrack pedigree is obvious to any aficionado of Yamaha's late '70s 'strokers. This whole project began, Dwyer relates, when friend and local TZ wizard Gary Bernstein mentioned a race bike going to seed down in Florida. The owner "decided he was keener on jet-skis than he was on reconstituting an exotic old two-wheeler." His loss. "I'd raced TZ350s for a number of years," Dwyer goes on, "so I sorta' had the 'TZ Disease.' " That forgotten Florida project bike was comprised of a disassembled motor, a great big bucket o' bolts and one complete Spondon race frame. It was pronounced "good" by another Dwyer mate in Georgia, but cobbling it all together would entail more than a quick stitch job. Clamp! Sutures! Circlip pliers!
Happily, a large selection of spares was included with the neglected bike. Those spares proved the dealmaker, as Dwyer the TZ350 campaigner knew parts for these pure race bikes were achingly expensive and exceedingly rare. Ultimately, the mélange was trucked from Florida to Maryland, by vintage Triumph racer John Gallivan.
Like most things worth doing, the rebuild took time and grit. "I was fooling around with it," Dwyer recalls, "between a ton of other things, racing a lot of bikes and go-karts - but I sort of pressed on." Like any good doctor, he consulted specialists here and abroad, ending up with a complete 1990 Suzuki GSXR750 front end and narrow-rimmed 1980s rear wheel, both from salvage yards. For the front, I machined up the various carriers for the bearings 'n stuff, to fit that. Then, I got an early Gixxer rear wheel with the correct 4 1/2" rim." (The first one was too wide at 5 1/2 inches). "King Kenny" also flat-tracked a TZ700 very similar to this 750, afterwards remarking, "They can't pay me enough to ride that thing!" "I machined the sprocket carrier, narrowed it down, sunk the bearing in and moved the sprocket in to fit inside the Spondon swingarm." After much machine work, he'd grafted the Gixxer 750 wheel, rotor and caliper onto the swingarm. "I narrowed the rear caliper, fabricated a caliper hanger and squeezed the package into the swing arm with only shim room to spare."
Yamaha produced some 300 of the big 700 & 750cc TZs in their 6-year production life, including a half-dozen variants. Some were superbike-class machines geared for "horsepower" tracks like Daytona, others for tighter European roadrace circuits, with a couple even configured as dirt-trackers. The best-known TZ pilot was Kenny Roberts. He won the big bike-dominated 19__ Daytona 200 miler on a TZ350! "King Kenny" also flat-tracked a TZ700 very similar to this 750, afterwards remarking, "They can't pay me enough to ride that thing!" The remark, along with the bike's smoky fumes, helped sound the death knell to the screaming racer and in fact all two-strokes in the 'States.He'd hoped to get an original TZ750 front end and rear wheel, but "They were incredibly pricey and not worth it you know, when I could find a setup that was much better for a street special." (Dwyer's a bit ho-hum about this work, but as is typical with specials, the entire process was maddeningly slow with countless cut fingers and binned "attempts.") The Suzuki's stanchions are several mil larger than the works items, and their four-piston brakes are a big improvement on the stock racer's two-pot items. Another key asset was the tubular Spondon frame, which mated with unexpected ease to the more robust Suzuki pieces. Dwyer explains that the "stiffer and stouter" British-made race frames largely did away with the flex problems of the factory iterations. (In the early 1970s, racers Kel Carruthers and Kenny Roberts commented rudely on the big TeeZee's handling).