Yamaha TZ750: Meeting The Monster

Patrick Bodden: I peer into the back of Russ Bigley's dingy gray Chevy van and get a face full of carbon-fiber two-stroke silencers. "Impressive," think, "this thing's the business!" After all, here was a seemingly competent example of one of the most legendary racing motorcycles of all time, the bike that struck fear deep in the heart of every manufacturer with large-bore roadracing intentions during the middle and late 1970s. If you had the balls and a decent racing rsum, and wanted a real chance at winning, even big-time, world-class winning, well then, mister, it was a Yamaha TZ750 or nothing.

"You wouldn't be alone in wondering if maybe the TZ750 isn't more than can be managed by mortal man. Plenty of people are having such thoughts. Reports in the foreign press have told of the TZ500's impact in GP racing, told of the stunned panic within the opposing MV team. Jarno Saarinen's death gave MV another 500cc championship, but the Yamaha's early performances would seem to give it a place of pride as the fastest motorcycle in GP roadracing history. What, then, might it be with more displacement, with virtually a pair of the engines that made Yamaha's TZ350 so formidable during 1973? The whole concept is intimidating enough to have given everyone pause." -- Gordon Jennings, Cycle, January 1974

Bodden: The TZ750 forged a well-deserved reputation as an unbeatable and unstoppable racer. But I'd been blinded by this bike's array of shiny new silencers. Unloaded in the dismal, soggy environment of our Daytona pit, the TZ looks tired and shopworn, and inspires little confidence. Boehm and I stand there gazing at it, not saying much for fear we'll come to our senses and go off in search of margaritas (for him) and root beer (for me). I break the silence first: "Well, Mitchie, we've not only got a vintage racer, but vintage workmanship to go with it!"

Mitch Boehm: I see none of the downsides at first. What I see is a real-deal TZ750, and a late-model monoshocker at that. I'd been in awe of Yamaha's big TZ since the summer of '76 at Michigan's Grattan Raceway. I'd gone there to check out a real roadrace with Dale Dahlke, an RD350/TZ250 mechanic who was tuning my XR75 and YZ100 motocrossers while running a small bike shop near my northern Ohio home. In an early practice session my 14-year-old senses were electro-shocked by a particular red-and-white two-stroke racebike that shrieked past the pits at what seemed to me an unbelievable rate of speed; had to be 130 or 140 mph. And the sound! Ear-splitting was way too tame a descriptor. After the session I walked the pits to see what sort of animalistic machine was capable of such mind-bending velocity and racket, and found it cooling menacingly in the pit of Midwest racer Robert Wakefield. I approached the bike from behind and saw smoke curling slowly from the skinny stinger exhausts. But it was the shredded, half-melted rear slick that lazered itself into my gray matter. Having never seen a warm and recently used roadrace tire up close, the sight filled me with genuine awe. I remember thinking, "This thing's a monster."

"Yamaha quite naturally has reservations about selling TZ750s to just anybody with money and a bag of brave pills. But AMA rules require 200 copies and you can't expect them to simply warehouse the production left over after Kel Carruthers takes what he needs. All the big fours will be sold, some of them to riders whose talents were barely equal to last year's TZ350. That thought plainly has the AMA spooked, because they know they don't have 200 Juniors and Experts who can cope with what it is feared the Yamaha will deliver. But there's nothing to be done now; Yamaha created the TZ750 in good faith and strict conformity with rules long-standing if not necessarily wise." -- Gordon Jennings, Cycle, January 1974

Boehm: Yeah, the TZ was a beast, but I still wanted to ride or, better yet, race one, ideally at a circuit with an equal measure of history. Daytona seemed perfect, and when Bigley offered up the chance to ride Kurt Lentz's bike (which Bigley took care of for Lentz), I jumped at the chance.

Bodden: I thought I'd seen the last of this sort of bike prep back in the '70s during my days as an East Coast club racer. Boehm said, "we'd" just have to make the best of things. Of course, the Heritage Racing guys have managed the impossible in impossibly short time so many times over the years that Boehm has come to expect this as an entirely reasonable approach to racebike construction--never mind we're dealing with a device, old as it is, capable of 170 mph even in less than top-notch condition.

Fact is, racing rsum or not, many a TZ750 fell into less-than-expert hands, meaning they didn't have much exquisite workmanship lavished on them. Nomatter. The TZ750, like its smaller brethren before it, was so inherently good and so naturally cooperative that, as long as the bike was reasonably well bolted together and no one went crazy with ignition timing and carburetor jetting, would go like fury and do so for a long time. Parts were readily available from local dealers and, as long as they were replaced as Yamaha prescribed, didn't often fail. Many a ratty TZ750--Miles Baldwin's and Richard Chambers' bikes come to mind--would allow a motivated and capable second-echelon privateer to upstage the more elegant (read: factory) front-runners.Bigley had had his hands full trying to prep two TZs--Lentz's bike and Bigley's own Spondon-framed racer--and the preparation he'd done wasn't meticulous. It was the rough-and-ready type that had sufficed all those years ago during the TZ's heyday. Problem was, there hadn't been enough preparation. The Lentz machine is a long way from something Boehm or anyone else would consider an acceptable risk on the racetrack. There's a lot of work to do, some evident and some yet to be discovered.

This hadn't been part of the bargain when Boehm presented me with his latest Daytona scheme a few months earlier. It was supposed to have been Heritage Relaxed Racing this time; just show up, look the bike over, check the tires and spark plugs, and let's have a go at it. But here it was, take it or leave it. Might as well get on with it, I thought.

Boehm: My plan going in, which I communicated ad nauseum in the lead-up to Bike Week, was simpler--and therefore potentially less angst-generating--than many of our previous vintage-racing adventures. Bigley had told me over the winter the TZ would be "basically ready to go" when it arrived in Daytona. He'd spooned a fresh set of sticky Avon vintage tires onto the bike's old sand-cast mags, and although heavy snowfall in New Jersey kept him from bumping the bike off and making sure it ran, he told me not to worry. Because AHRMA didn't have a class for what's arguably one of the most historic racing motorcycles in the world (highly ironic, considering it's the American historic Racing Motorcycle Association), I planned to run the TZ in the Championship Cup Series' Formula 40 event, which allowed any racebike but was limited to riders aged 40 and older.

Bodden: When you're in trouble you turn to your friends. And if there aren't enough of them, you draft innocent bystanders. Heritage Racing partner R.L. Brooks is a long-time friend who's helped me through more than one Motorcyclist vintage-racing adventure. He and I make new friends on the spot--Phil DiGiandomenico (whom we'd met briefly a few years before, and father of Jimmy and Tommy) and congenial but unsuspecting TZ750 racer (and Brit) Mark Middleton, to name just two.

We size up the situation from clues provided by Bigley and our own sleuthing and chart a course of action. Someone detects excess fork oil on the tubes right away, so Boehm is wise to at least one problem. No big deal. Bigley has new seals, so R.L. and Phil D. get busy replacing them. As is so often the case with seemingly minor problems, unforeseen snags ground our resolution to a halt. The guys aren't any sooner into the job than they're stalled by the Allen bolt holding one of the fork legs together; its internal hex is no longer hexagonal and the bolt isn't responding to wrenches or cusswords. It's off to locales with better weapons--DiGiandomenico's nearby Daytona garage--where extracting the bolt proves fairly easy, even if it means destroying it in the process. Of course, it isn't a garden-variety piece--it's of an exotic thread pitch/diameter, and much running around reveals that a replacement isn't to be found in all of Daytona. Back at DiGiandomenico's home machine shop, a different-style bolt has its head turned on the lathe and a slot sawed into it to substitute for a hex. We're back in business. A one-hour job takes two capable and resourceful technicians an entire day.

Meanwhile, I'm working through my own misery. Carburetor synchronization, in particular, seems either interminable or impossible, I can't decide which. This thing might be a legendary motorcycle, but its carburetor linkage--four individual cables from throttle to carburetors--is becoming a legendary pain in the ass. Get three just right and I run out of adjustment on the fourth. Get four more or less OK and, if I move the cables a bit reinstalling the fuel tank, the carbs go out of sync again. Finally, when everything seems reasonable, I discover a crack in the top half of the throttle assembly. Bless his heart, old Bigley (working feverishly on his own TZ) just keeps the parts coming and offers up a replacement for the cracked piece. The new part installed, I check carb sync for the thousandth time and pronounce it fine.

As the day rolls by I keep finding things to do or fix. Racebikes are like infinite sponges of time and resources. All done (or so I think), I step back, admire how simple it all looks, and wonder how preparation--and replacing a few parts--could possibly take so long. Of course, there are other concerns, such as, would the bike be safe for Boehm to ride? At this point I'm not sure.

Boehm: By this point I'm horribly frustrated. We'd planned to run the bike in today's informal Team Hammer practice so I could get accustomed to it and the revised, much-tighter Daytona circuit. Not a chance. And the way things are going, getting any practice the following day looks iffy at best. Not a good start.

Bodden: A Daytona day has come and gone. Boehm announces quitting time (with help--via threats--from the ear-bleed PA system) and herds the crew to the local Mexican eatery, the Cancun Lagoon. A veritable food fiesta ensues, the first of three consecutive such sorties. The fare is acceptable, as are the margaritas (so I hear), some of them doctored with what looks like blue toilet bowl freshener. The more everyone drinks, the better everyone pronounces the food. By evening's end we could have substituted linoleum for taco shells and Boehm & Co. would have pronounced them mucho splendido.

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.

Sunday dawns clear and bright, and the crew arrives early to check the bike in anticipation of the precious few practice laps I'd been granted. We get the bike through tech inspection (raised eyebrows galore) and warm it up along pit row, which attracts a crowd. As Bodden blips the TZ's throttle, rapid-fire smoke bursts and two-stroke Brrraaaam! sounds fill the air, and I have the feeling ghosts are stirring throughout the Speedway's towers and garages. It'd been many years since that unique four-cylinder/two-stroke sound had ricocheted off these legendary grandstands. Speedway announcer Richard Chambers, who'd ridden TZ750s to some exceptional finishes back in the day (and who still has his TZ racer), rides by on his scooter with a knowing smile on his face. He tells several old-school tales over the PA system about Kurt Lentz and his TZ, which I'm about to ride.

"A hard shove gets the Yamaha rolling. You work it up to a trot, then hop on sidesaddle and bang in the clutch to spin the engine, which responds with a few raspy barks before settling into a sullen staccato as you head for the course. At first you go gently, waiting for the water-temp needle to lift off its peg, teasing yourself with short bursts of speed. One full lap, then another half-throttle tour of the infield before you let yourself fall into the familiar racing patterns, pulling the bike upright and rolling on throttle as the last yards of the final infield turn flicker past." - Gordon Jennings, Cycle, January 1974

Relatively speaking, the TZ750 is a tiny motorcycle, more like a current 250 than an open-classer. I'm reminded of this as I roll down pit lane for the first time and enter the track just before Turn 2--the International Horseshoe. The cramped seat-to-peg layout makes it really hard to move my body around on the bike through the much-tighter infield, and by the time I accelerate onto the back straightaway a quarter-mile before the chicane, my calves, quads and lower back are already cramping."With that the busy, four-cylinder snarl becomes a hard, hammering shriek and the Yamaha hurls itself at the high south banking, its front wheel almost too light to steer. Quicker than memory it claws its way around and flashes out along the back straightaway, tach needle surging next to the red pie-slice as your toe twitches at the shift lever. All the sensations are familiar but of a magnitude that reaches past the limits of experience. Speed blurs everything but a narrow tunnel ahead. Wind buffets and plucks at your leathers, and a rash of heat from the radiator sears your face." -- Gordon Jennings, Cycle, January 1974

The TZ feels incredibly light and whippy despite the narrow (and low-mount) clip-ons, which offer little leverage. The bike seems to respond to weight transfer as much as bar pressure entering corners, and I find I can get fairly aggressive with it early on. Midrange power is surprising, but I'm taking it easy at first; Bigley told me the engine was fairly fresh and probably needed a few laps to get up to temperature before I flogged it. Both ends feel way soft, but it's not a problem at the speeds I'm running. The brakes are positively wooden, but I'm used to that. Luckily, the Avon tires warm and scuff quickly, and keep me from worrying about grip--unless the back tire suddenly gets oiled up, that is.

You clamp your knees against the tank more tightly and sneak a finger forward to tug at the brake lever, just checking. You never did that before, but you do it now. Moments later you're braking for the chicane, downshifting, hauling at the handlebars and feeling the tires shudder. Then you're driving hard into the north banking, hunching forward to keep the front wheel from lofting, waiting until you have it aimed before using all the power, bracing yourself for the bike's awesome, catapulting acceleration. And forming in your mind is the nagging thought that while sure as hell somebody has done the right thing, somebody at Yamaha, what they've done just might not be the right thing for you. -- Gordon Jennings, Cycle, January 1974

By lap five I'm starting to get into the groove despite my cramping legs. The thing is fast. But then I notice the temperature gauge as I head for the tri-oval; it's gone past 90 degrees Centigrade and is heading for 100, which Bigley called the danger zone. I imagine being flicked off into Turn 1 as the engine seizes, so I back off and roll into the pits a lap later, thinking unhappily that these might be my only laps till my race later in the day.

The crew goes over the bike while I head for the CCS office to double-check my race time. Two hours later we're pushing the bike to start/finish and the butterflies are swarming. Not because I'm worried about being competitive (I'm gridded last, and in a class filled with late-model R1s, GSX-Rs and ZX-10s!), but because I want the bike to last, want to make it back in one piece, want to bump right up against this thing's ragged edge and see what's there. Dunlop's race-tire guru Jim Allen walks by and gives me a thumb's up, but wonders privately about the bike's magnesium wheels, which are known to become brittle with age and disintegrate at speed. He keeps his concerns to himself, which is probably a good thing.

I take it easy at the start and use the first lap to get re-acquainted with the bike. My goal is simple: Run the thing as hard as I can, and hopefully catch a few backmarkers so the race feels like something more than a practice session. The TZ feels reasonably good entering the chicane on lap one so I carry extra speed through the exit and hammer the throttle. The bike shakes its head under power but remains true, and I've got myself a decent drive. I can hear the TZ's raspy exhaust note bouncing off the wall of the banking, and it sounds great. Time to see how fast this thing is. Ripping off the east banking a quarter of a mile later headed for start/finish, the bike bottoms forcefully on the roller bump at the banking's exit and goes into another speed wobble at what must be a buck-fifty. Roberts wasn't kidding.

The shimmy's not bad enough to cause me to back off, and I carry Big Speed past start/finish. But I blow the entrance to Turn 1, arguably the toughest bend in all of motor racing. Through the Horseshoe and the rest of the neutered infield I'm having a hell of a time getting any sort of rhythm going; the brakes are weak, the bike has little engine braking on deceleration, and though I'm riding a lot faster now than I had in practice, I'm lurching all over the place--and surely looking like an idiot on an old bike floundering at the back of the pack in the process.

The bike wants to wheelie through the gears exiting the infield onto the back straight, but I'm more worried about the oily mist that seems to be rising from around my crotch. I sneak a look down at my right thigh and knee and find the leather there shiny with petrochemicals. It's just the gas/oil mixture backwash through the carbs and intake system typical of most two-stroke racebikes, but I don't know that--and images of oil-coated rear tires begin playing on the insides of my eyelids. Pitching the bike into the chicane five seconds later at 90 or 100 mph takes mammoth faith, but there's no slide. Guess it's OK.

I try to get ready for the high-velocity shake/shimmy that's coming through the east banking's G-out, but my attention is focused on an almost unreal level of vibration and noise permeating the cockpit. It's way worse than I remember, so I naturally think something's gone terribly wrong. What's happening is that I'm riding the bike a lot faster now, and it's doing what big, nasty two-stroke racebikes do at speed. But again, I don't know this, all of which keeps me from nailing Turn 1 again. The temperature gauge again flirts with the 100-degree C mark, but I ignore it. Bigley said to.

By this time both my feet are asleep and buzzing with pins and needles due to reduced blood flow caused by my pretzeled legs, but there's too much craziness happening to think about them now. I get a bit overzealous exiting the Horseshoe, lose the back end in a lurid slide and almost run off the track after I get things buttoned up. The bike rockets toward the tight section of the infield and I nearly overshoot the right-hander due to my right hand cramping from grabbing the brake lever so hard for so long. I tell myself to relax, but my rapid-fire breathing fogs my shield and I miss my turn-in point two corners later. I can see folks in the grandstand as I rattle by, and I just know they're laughing their asses off.

I realize I'm tired and riding out of control--and then I get the crossed flags that signal the race's halfway point. still four laps to go? Damn! It's not so much the power that's making the TZ hard to ride; power hits hard at 7000 rpm and redlines at 11,000, so there's a decent spread there. The problem, for me at least, is that the engine is so much better than the chassis. The soft suspension, weak brakes and racklike ergos are taking their toll, making me ride spasmodically, unable to be smooth. Somehow I manage to relax a bit ripping along the banking, and I wonder briefly how riders--especially those larger than average--rode these things at race speeds for 200 miles here. Amazing.

In the race's latter stages I manage to put together a couple of decent laps, and even catch a few slower riders--although Team Yamaha's Jason DiSalvo and Jamie Hacking lap me toward the end while testing for the AMA races the following weekend. At the checkered flag I pull in and collapse onto the TZ's tank as I roll to a stop where Bodden is standing. Hacking and DiSalvo come over to check out the bike, as does Jim Allen, who then tells me of his concerns about the mag wheels. Someone says they got me at 168 mph on radar, which makes me extra happy the wheels stayed together. Hacking breaks us all up with his quip, "My mountain bike's got thicker fork tubes than that thing!" DiSalvo throws a leg over the TZ's saddle and fits perfectly; he says he'd like to try riding it sometime. Allen, who rode his share of race laps on big TZs, laughs at the thought. But we all know DiSalvo would be crazy-fast on the thing.

Bodden: I'm relieved afterward, just as I'd been 10 years earlier when I'd watched Boehm race the Drixton Honda 500 I'd prepared (the very reason we were having this 10-year commemoration at Daytona). I was afraid there might be some problem I didn't know about--and didn't have time to find--lurking deep within the TZ. I felt a great sense of privilege being able to work on one of the most legendary racing motorcycles of all time. The few moments I wasn't preoccupied during that long weekend, my head was filled with images of Agostini, Roberts, Johnny Ceccoto, Steve Baker, and, as a compatriot, of Patrick Pons and his win at this very circuit in 1980. I also reminisced about local greats, some champions, some not--Chambers, Rich Schlachter, Greg Smrz, et al. I reminded myself that, despite all the apprehension surrounding the TZ750's release, and despite its mind-boggling acceleration and top speed, it earned an enviable safety record. It may have been fierce, but it wasn't vicious.

Boehm: I'm spent, but hugely jazzed about the way it all came off. By riding the TZ hard in a real roadrace at Daytona, I'd gotten a firsthand glimpse into a large portion of American roadracing's history. Lentz's TZ wasn't quite the monster I expected. But the experience did show me the monstrous skill and determination of the riders who went fast on them back in the day. Amazing stuff. MC