I’M sitting on a bike I once only dreamed of touching. This seat is usually reserved for genuine racing heroes. Kenny Roberts and his son are among the very few who have graced it.
The mid-day Californian sun beats down on me, sweat beading under my visor. My heart is beating just that little bit faster than it should – senses on fire from a heady brew of two-stroke and a disbelief that I’m actually awake while all this is happening.
I’m on a bike that makes today’s GP 500 racers look like user-friendly pussycats. While the racers you’ll have seen at Donington Park at the weekend may make 180bhp, they put it down through a tyre the width of a bus and with the aid of the best suspension technology the 21st Century can offer.
I am on a Yamaha TZ750. It’s a two-stroke, in-line four-cylinder monster from a time that sanity forgot. It makes 120bhp and puts it down through a tyre skinnier than Kate Moss before breakfast.
The TZ750 was the ultimate race bike of its day – dominating the Formula 750 class on the world stage and the equivalent of the superbike championship in the UK. And in the mid to late ’70s I believed their riders were supermen.
And this example’s owner, American Nick Ienatsch, wants me to give it some beans.
" Jim, don’t be afraid to rev it, it’s pretty tough. " I don’t need asking twice...
Resting on the thinly padded seat, I am almost dribbling at the prospect. This is one of my all-time dream bikes – and one that very few people are ever allowed a crack on.
This thing is tiny. It feels almost half the size of a modern 750cc superbike. Even my little legs allow my feet to be flat on the hot Tarmac.
The rev counter bears a red line that starts at 10,500rpm and the all-important water temperature gauge rests in a foam mounting bracket. A neat custom-made alloy bracket holds aloft the RC30 front brake master cylinder. All the switchgear on this beautifully-crafted rebuild is from a Honda RC30.
I snick the bike into first gear – upwards in true race bike style. The dry clutch spins as I push the TZ down the hill, bringing the engine to life. I blip the heavy twistgrip, keeping the motor spinning above 5000rpm. Anywhere below that figure isn’t taken well.
A quick glance at the temperature gauge shows the motor is ready for more and I turn on to a slip road to crest the short uphill drag to the freeway. As I change into third I hardly notice that the TZ’s front wheel is a foot in the air. The short chassis is so well balanced it hovers effortlessly.
I tuck down behind the smoked bubble of the fairing and find myself daydreaming about what it must have been like driving off the high Daytona race track banking at over 180mph – blasting into the braking zone heading into the right-left chicane. Chasing a whole bunch of shrieking two strokes, the noise in your helmet must have been immense.
Five miles later, after playing with the traffic and getting to know the power of the TZ, I head for some canyon action. I run up and down a two-mile section of sweeping bends, starting to give the big two-stroke some stick and enjoying myself. Now its time to really kick its guts.
The same section of road is transformed. As I twist the throttle to wind the big motor’s reed valves open, the rev counter dives into the blood zone. It feels like I’m short-shifting just to keep up with the rev counter.
The suspension allows you to go where you point but it beats your ass, buzzes your body and even gives you a pain in the eye sockets. Firm but fair. The body pummelling makes you feel good – like a Turkish massage.
And the front end... even though it’s fitted with a steering damper and forks from a more up-to-date Kawasaki ZXR750, the power from the engine hits with such a rush it patters all over the road – and that’s only at 90mph. God and some god-like riders know how it must feel at 150mph. We definitely have it easy these days.
I can hear the four carbon tail pipes spitting fury. As I glance across at the bike’s owner I can see he’s grinning from ear to ear. He loves it. Every time I flash past I give it some more grief. I can feel the chassis fighting to keep the wheels on the ground.
Right now I’m in heaven. This is raw power at its finest. The braver you get with the throttle the closer you get to two-stroke Utopia.
In my short time on the TZ I’ve answered a thousand questions that have been rattling around the back of my mind for 20 years. If it wasn’t for the TZ700 and TZ750s we’d have had to do without Barry Sheene, Kenny Roberts and Freddie Spencer.
They only weighed 152kg (335lb) and blitzed allcomers. If you didn’t have a TZ 750, you weren’t even in the ballpark.
For almost 10 years, they dominated race tracks around the globe. And in those days you and I could buy one. Imagine being able to buy the equivalent of a Honda NSR500 for the same money as an R1.
If you or your tuner knew what he was doing, you could end up with a racer that could take on the best " factory " bikes around.
I would watch in awe like everyone else as the likes of Ron Haslam, Mick Grant and Steve Parrish wrestled the spindly-framed beasts, suspension fighting to keep the wheels on the deck as the narrow power band kicked both machine and rider around the track. And that was in the dry. To see 40 TZ750s race in the wet was a lesson in Teflon-coated chaos.
Their day eventually ended – hastened by the arrival of Suzuki’s RG500. They became confined to the backs of damp garages, hidden under blankets, or simply sold into club race obscurity and inevitable destruction.
So when American motorcycle journalist Nick Ienatsch came across a 1978 spec one for sale he bought it – without even taking a cursory look at it.
When the crate was opened, to Ienatsch’s dismay the TZ750 was a wreck. In disgust, he wheeled the TZ to the back of his workshop. Where it sat for another five years.
Somehow chassis expert Chris Geiter, from Allentown, Pennsylvania, heard about the old TZ. Every few months he would talk about taking it back to his workshops and rebuilding the " pile of junk " . In the end Ienatsch gave in, but with the proviso that it became a street-legal machine.
When the TZ finally arrived from Los Angeles in the back of a shipping truck, he realised there was more to the rebuild than getting out a wire brush. Parts were missing and the bike had started to deteriorate. The frame was broken in two places.
" I didn’t know where to start. In fact, I didn’t know if I should start at all, " says Geiter. But Geiter’s memories of a youth spent staring slack-jawed at bikes just like it got him going.
He yanked out the motor and sent it back to Los Angeles, to two-stroke expert Steve Biganski. When Biganski stripped the four cylinders he found serious damage to the crankshafts, the crankcases themselves, barrels, pistons and gearbox.
With no new parts available, he spent considerable time on the phone pulling in favours. Biganski had raced the
TZ750 back in the ’70s and had friends who still had TZ bits and pieces in storage – people like Don Vesco, Jim Reed and Kel Carruthers. He even tracked down the owner of the TZ750 dirt-trackers raced by Kenny Roberts and Stevie Baker in the mid-70s.
Back in Pennsylvania, the serious chassis work began. Precision Chassis Fabrication chopped the snapped frame tubes out and replaced them.
They added mounting brackets for the necessary bits and pieces to make it road-legal.
The three-spoke Dymag magnesium wheels were sent to Connecticut Cycle Refinishers to be crack tested, stripped and repainted.
With most of the major components back in Geiter’s workshop, the rebuilding began.
Geiter wanted light. He banned heavy steel bolts, having one-off titanium bolts and aluminium brackets machined to order.
" This was a once-in-a-lifetime chance to build a dream bike, and dreams should be done in full Technicolour, " he says.
The standard Yamaha front end was beyond repair. Geiter grafted a set of modified Honda RC30 triple clamps to Kawasaki ZXR750 fork legs, re-valved to cope with this lighter bike.
The Yamaha’s old twin-piston brakes were replaced with Performance Machine billet four-piston calipers with 310mm full-floating rotors. The rear brake got a new 255mm rotor matched with a twin-piston caliper.
The only piece of bodywork to escape the skip was the fuel tank, stripped and primed. Geiter sourced a set of bodywork and a TZ750 fairing which would now hold the single headlight. He added a TZ500 single seat unit. He even managed to find a distributor who, after all these years, still had a brand new TZ750 screen in stock!
At last only the finishing touches were needed. A set of Dunlop K591s was spooned onto the freshly restored gold Dymag wheels. Yamaha France racing colours finished the job.
The TZ was loaded into Ienatsch's pick-up truck and driven to Kenny Roberts’ ranch for its debut.
" Kenny spent 20 minutes flashing back and forward pulling second and third-gear wheelies! It was just like the old days at Daytona... "
To date the only major problem has been with an errant first gear. With no spares on the shelves the old gearbox ‘dog’ was welded, recut and then heat-treated to sort it.
Ienatsch won’t say how much it has cost to make his childhood dreams come true. Like myself, Ienatsch is truly passionate about his TZ, he raves about it. You get the feeling that whatever it cost him, he feels it is money incredibly well spent.
Even sitting dormant on its rear stand at the end of my magic moments on board, it still has the power to captivate.
I now have a quest, a burning desire. One day I’m going to find myself one of Yamaha’s old four-cylinder two-strokes. Maybe in 20 years I’ll allow someone to test my bike.
I’ll choose very carefully, as Nick Ienatsch did and I’ll make sure whoever does it knows how great the favour is I am granting them. One day...
TAMING THE BEAST…THE ROBERTS WAY
KENNY ROBERTS SNR first learned how to tame violent, powerful two-stroke beasts on a TZ750. The battle gave him all he needed to go on to become a GP legend.
But for a rider with his level of skill, taming the TZ was nowhere near as hard as us mere mortals would find it.
" It’s a misconception that they were real nasty, " he said. " Only when you pushed the early brutish 750s did they get real out of shape. As the tyres would start to wear throughout the race the chassis would get out of shape.
" Some riders would just pull in and retire when their tyres wore out. But because of my dirt-tracking background I could almost ride around it. The later TZs like the OW31s were so tractable they would pull from 4000 revs. Even on wet tracks, because of the way the motor pulled, they were great.
" The biggest problem I ever had was snapping the rear wheel chain adjusters. With the short swinging arm the rear suspension would tie itself in knots. They were pretty simple to set up, as there was literally no adjustment. So it was who was prepared to run it against the guardrail that would win. At tracks like Daytona, we would be running top speeds around 190 to 196mph depending on gearing.
" All the non-Japanese works riders’ bikes were almost identical. The Japanese racers’ bikes were always faster, though. Strange thing that. On some tracks the front end would get so out of shape I would have the mechanics rebuild the steering damper, drilling out the internal valves and refilling them with 30 weight motor oil. "
So that’s what Kenny Roberts Snr means by something that isn’t " real nasty " . Thank you Kenny. It’s been an education.
Engine: Liquid cooled, 747cc (66.4mm x 54mm) two-stroke in-line four. 4 x 34mm Lectron carbs. 6 gears
Chassis: Tubular steel double cradle
Front suspension: 43mm Kawasaki ZXR750 forks, adjustments for pre-load, compression and rebound damping
Rear suspension: Single shock, adjustment for pre-load.
Tyres: Dunlop K591; 110/80 x 18 front, 140/80 x 18 rear
Brakes: Performance Machine; 2 x 310mm front discs with 4-piston calipers, 225mm rear disc with 2-piston caliper
Power and torque: (est) 120bhp, 78ftlb
Weight, power to weight ratio: 152kg (335lb), 0.79bhp/kg
Top speed: 170mph (geared for the road)
Geometry (Rake, trail, wheelbase): 26°, 9.7cm, 139cm