Yamaha TZ750: Meeting The Monster

From roach to racer in three easy, fun-filled days. (Ha!) We go butt-to-saddle at Daytona with the most notorious and successful roadracing motorcycle of the 1970s--Yamaha's TZ750

By: Mitch Boehm, Patrick Bodden, Photography by Catherine Brennan, Tom Riles

The next day is a repeat of the first, but this time the rear master cylinder is the Daytona Gremlin of the Day. According to Bigley, all it needs is a good bleeding. Boehm says bleeding is unnecessary, as he "never" uses the rear brake. (Funny how he manages to return every racebike I build for him with a seriously blued rear disc. Maybe not Cancun Lagoon blue, but blue just the same.) R.L. and I run fresh fluid through that legendary magnesium TZ750 master cylinder and can't get any pedal. We remove it only to find a punctured seal and big-time corrosion. Bigley announces that seals for these things are extinct. Now what? I notice 5/8 cast into the cylinder body and opine that an American or British seal might work, especially since it looks ordinary in every respect. Another tour of Daytona parts purveyors produces two likely candidates--a seal kit from an auto parts store for Lord knows what, and another for some Harley. I opt for the Harley part, and it works. Close enough.

Photographer Tom Riles is sympathetic to our plight, and although he seems to believe all this commotion is futile, he records it. He also holds the master cylinder while I hone legendary corrosion out of it. We reassemble everything and in short order have a functioning brake. Trouble is, the pedal now contacts one of the exhaust pipes. We run out of adjustment rod trying to fix it, and once again a modified garden-variety bolt is substituted for an OEM part and we're in business.

We munch Boehm's worker-compensation food--burgers, Milky Ways, sodas and Gatorade, but no blue drinks--and survey our progress. We now have a functioning, non-leaking fork, proper throttle action and working front and rear brakes. Paul Thede of Race Tech makes the TZ's yard-long single shock/spring unit work as well as he can with limited tools. Everything seems reasonably bolted together. We have water in the radiator, oil in the gearbox and premix in the tank. Do we have spark? We have faith.

Time to start the beast. After a spirited push the TZ comes to life in a grand spasm of sound and smoke. The smoke clears, and so does the exhaust note. I let it rip up the pit road. By God, it feels good and sounds fierce! I turn around and let it rip again. I'm thrilled, and so are the guys. The track Gestapo is less so. I can't hear him even at the evil PA system's 120db volume, but he's issuing threats of eviction if I don't cease and desist. I hear of the threats back in our pit, but I don't care. We're not hurting anybody. Maybe scaring a few people, but we're not endangering anyone.

The bike is beginning to look pretty good; Riles even calls it photogenic. It's scuffed and more than a little shopworn, but it's getting cleaner by the hour. Our second Daytona day is over and it's back to the Lagoon for more Mexican food and blue drinks.

Boehm: When the TZ lit off I was jacked! It sounded so cool, so crisp, just like the 500cc GP bikes I'd seen and heard at Laguna back in the day. I knew it'd be a rocket, and couldn't wait to ride it. After all the myths that'd circulated about the big TZ, I'd finally get to see what the monster was really like. Problem was, we'd once again run out of time for practice, and tomorrow was the Formula 40 race. I was highly pissed--which meant more margaritas that evening to drown my sorrows.

Bodden: Day three is race day, and we go backward. The front brake decides to quit working. We bleed it, and it comes back to life, but it isn't ideal. The crew knows we're running short of time and works with Boehm on control positioning, all the time cleaning this and that, checking fasteners, installing breather hoses and catch bottles, etc. Then there's some business with two of the plug wires. The bike starts, but reluctantly, and has a case of what Kevin Cameron once referred to as the piff, paff, poofs. Sometimes two-strokes do this and then clear up. This doesn't clear up.

Back in the pits it's decided the other two wires also need to be changed. But now the bike won't start at all. That's progress as far as I'm concerned and I say so, asserting the wires needed to be put back as I remember them regardless of what the book said. No one listens to me. Middleton appears, doesn't say a word to anyone, and repositions the wires just as I said they should have been in the first place. We push again and the bike starts. During all this frantic back and forth, practice and the Formula 40 race have come and gone. Like all of us, Boehm is not a happy man, and it shows.

Boehm: At this point I was in a foul mood. We'd missed every lap of practice along with my scheduled race. Luckily, CCS head honcho Kevin Elliott, who I'd been hounding every hour for what seemed like days, gave me the go-ahead to take part in a short practice the following morning (Sunday) and a Superbike-spec race later that afternoon with highly modified modern bikes. My goal of actually riding a legendary Yamaha TZ750 in anger wasn't dead yet.

Even so, I worried plenty that evening at dinner, our third in a row at the now-infamous Lagoon. The TZ's front and rear suspension remained way soft despite dialing in max preload (the springs were too soft), and damping seemed non-existent. Kenny Roberts Sr. told me a month earlier to get up off the seat on the banking, that the bike was "sure to wobble." Considering the thing was capable of 170 mph, this did not sit well, even with several blue drinks circulating through my system. (Who says alcohol makes you brave?) There was more: I barely fit on the bike. Seat-to-peg distance was a scant 13 inches, way less than even the sportiest of sportbikes, and lifting my feet onto the pegs while seated was a challenge. My knees hit the fairing sides once I got seated, and I wasn't sure the cutting we'd done to the fiberglass would be enough. And what of carb jetting? Would it be rich, which might have the bike loading up on the start line? Or would it run lean, and seize solid exiting the chicane, highsiding me into a cement wall at 80 or 90 mph?

And even if all of that stuff turned out to be workable, how difficult would it be to ride quickly? Stock TZs--at least the early twin-shock versions--made around 90 horsepower. But Bigley had told me Lentz's bike sported radically ported cylinders, Lectron carburetors, new-generation reed valves and modern expansion chambers, the end result being somewhere between 120 and 130 rear-wheel horsepower. That doesn't sound like much relative to today's 150-horse open-classers. But when you're talking about a 346-pound machine with famously abrupt power, mean-Alice handling, soft, damping-less suspension, skinny tires and a reputation for extreme wobbles at speed, all on a racetrack I'd not yet ridden, I was beginning to question the entire scheme.

By Mitch Boehm, Patrick Bodden
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