Tag Archives: Honda

Archives: Blue Bolide


The Suzuki holds its line and changes direction easily.

The scene is the final hour of 1988 24 Heures De Leige at Spa in Belgium.  Suzuki France lead rider, Herve Moineau, waits nervously in the pit, quietly preparing himself for his final session on the GSX-R750.  After 23 hours of racing his teammate, Thierry Crine is leading by just 15 seconds from the Honda France entry.  But it’s not just the race that’s being decided on the track it’s also the World Endurance Championship.

The Honda pits first, Bouheben climbing exhausted off the ’87 model RVF that team manager, Jean-Louis Guillou, has entered in preference to the less reliable ’88 version.  Alex Vieira mounts the Honda to the clak-clak-clak of chief mechanic Coulon’s air gun as the rear wheel is changed.  Only 11.5 seconds have passed when Vieira blasts out of the pits.

A lap later Moineau is staring intently down pit lane waiting for Crine to come in.  The blue overalled mechanics ready themselves as they know the slightest mistake can cost them the Championship.  Crine dives into pit lane and hands the GSX-R750 Suzuki to Moineau who is refuelled and out the pit in 6.27 seconds.  Suzuki Team Manager, Domonique Meliand, stands by the pit wall, stop- watch in hand, ready to time the split as Moineau flashes by on his first flying lap, before flicking left then right through Eau Rouge and out of sight – but where’s the Honda!

45 seconds later Vieira’s Honda drones past. Word spreads down pit lane that on the last lap of his stint, Bouheben, who had heroically made up 13 seconds on the Suzuki, dropped the Honda at the bus-stop chicane before handing the RVF750 to Vieira.

The race and the championship are Suzuki’s, beating their great adversary, Honda, in the last year before the series loses its World Championship status.

*          *          *

Later that month half a world away, at Sugo in Japan, Suzuki scores its first win in a new production based World Championship, the World Superbike Series, with its new J model GSX-R750.  Yoshimura pilot, Gary Goodfellow’s win, however, is put down to luck, as the first leg victory was more the result of a tyre gamble, and in the second leg, an oil spill affects the outcome of the race.  Suzuki know they are in trouble as the privateers complain about the F.I.M.’s stock carburettor ruling, bemoaning the J models 36mm slingshot CV carburettors that won’t let the engine run cleanly at the top end, and even Yoshimura is having trouble getting horsepower from the new short stroke motor!

*          *          *

It was the culmination of these significant events that prompted Suzuki to produce a more competitive motorcycle for Superbike racing in 1989.   Taking a leaf out of Honda and Yamaha’s book, Suzuki has released the GSX-R750R, built specifically for Superbike homologation, and basically a road-going replica of Suzuki’s Endurance World Championship winning machine and its F1 racer.  Suzuki Australia brought 50 of these $19,950 beauties into Australia last September, with six earmarked purely for racing (no A.D.R. compliance and $500 cheaper) while the other 44 are fully road registrable.

Jeff Zammit, the owner of Adelaide’s Suzuki South, was kind enough to let Bike Australia borrow his personal GSX-R750R for a ride impression.  Jeff’s RR (I will refer to Jeff’s bike as the RR so as not to cause confusion with the standard RK model) had 800km on it when I picked it up but was fully run in after some careful kilometres on the road and a bit of stick on the race track.  But before we go any further let’s have a look at what makes the RR cost $11,000 more than its similar looking stablemate.

Suzuki looks purposeful but "pretty".

Suzuki looks purposeful but “pretty”.

The heart of the RR is its engine, and there are plenty of changes.  The carburettors are new BST 40mm CV items, up 4mm from the RK model and big enough to swallow birds and small dogs!  They feature easier resetting for race conditions and have a high-speed power jet which allows a leaner main jet for better mid-range throttle response.  Also improving throttle response is the atmospheric venting of the lower side of the carburettor diaphragm.  On the RK this is vented to the air-box where intake pulses can affect the pressure under the diaphragm and in turn throttle response.

A magnesium cover graces the factory-racer spec cylinder head, which features a valve system identical to the works racer and uses titanium nuts for valve adjustment.  Spark plugs are a new cold-type dual-electrode design by either NGK or ND with a smaller thread size of 10mm.  One reason for the change to a smaller thread size was to eliminate cracking in the combustion chamber that had occurred on RJ and some RK models used for Superbike competition.  The RR also returns to the four-into-one exhaust system of the earlier models but with a lightweight stainless steel design that uses an aluminium muffler.

Another significant change is the return to the old bore and stroke dimensions of 70.0mm x 48.7mm of the G and H model as opposed to the 73.0mm x 44.7mm of the shorter stroke J and K model.  One of the benefits the longer stroke provides is more time regarding crankshaft degrees for the cylinder to charge, which in turn increases port velocity.   The crankshaft is a high-rigidity lightweight unit, identical to factory racer, as are the conrods, which spins to the same 13,000rpm redline as the short-stroke RK model.  Horsepower has increased over the RK by 8ps  to 120ps at the same 11,000rpm and torque has improved from 7.9kg.m to 8.3kg.m again at the same 9,500rpm. The clutch has received an extra drive plate and the cooling system now features a curved radiator from the GSX-R1100 with a sub-cooler for the cylinder head to help deal with the increased thermal loads the optional $17,000 full race kit can create.

The chassis looks the same as the RK but has been strengthened around the steering head, and the swingarm is also heavily braced.  The front forks are of the inner- cartridge type, with beefy 43mm stanchion tubes that provide step-less spring preload and 12 positions for both rebound and compression damping.  A Showa remote gas shock is used at the rear with preload varied by screwing the spring collar up or down while a knob on the remote reservoir handles the compression damping and extension damping can be adjusted from the bottom of the shocker.  Wheel travel is 120mm for the front and 136mm at the rear, which is about par for the course for a serious sports bike these days.  Steering head rake is 30 degrees with 102mm of trail which is a bit slower than the RK’s 24 degrees 50 minutes and 99mm trail although the RR has a 5mm shorter wheelbase.

Racing riding position necessitates regular stops.

Racing riding position necessitates regular stops.

The Nissin four spot calipers of the RK set a high standard for its class and are retained at the front, but utilise slit-type floating disks from the GSX-R1100.  These are 5mm thicker than the RK’s and do a better job of drawing heat away from the pads, thereby reducing heat transfer into the calipers.  Wheels remain 17inches in diameter with the front the same 3.5inch width, while the rear is a massive 5.5inch job that takes advantage of Michelin’s latest fat low-profile road going radial and more obviously the current crop of racing slicks.  Tyre sizes are, up front an A59X 130/60 ZR17 and at the rear an M59X 170/60 ZR17.

The fairing is a quick-fastening two-piece affair of high cooling efficiency and low aerodynamic drag.  Suzuki has special sand-cast engine casings like those of the endurance racer to help reduce frontal area and give the RR a higher angle of lean.  The front fender and seat cowling are identical to the factory bike, and all the bodywork is made from fibre reinforced plastic that’s suitable for racing conditions.

The seat rear subframe is of aluminium/steel construction and for solo use only.  A nice touch is the maintenance free battery that resides under the seat and is canted back at about 45 degrees so it will fit the confined space.  It no doubt helps, in some small way, the centre of mass of the bike.  Also, the seat bum pad is removable and can be unlocked with the ignition key.  This reveals two small storage spaces, one of which houses the toolkit.  The fuel tank holds 19 litres – 2 less than the RK and is styled after the F1 and endurance bikes.

Visually the RR is quite stunning – purposeful, but with a rounded shape and curved lines that to my mind can only be described as “pretty”. It’s also very compact and weighs just 187kg dry (8kg less than the RK) which makes the RR seem smaller than its capacity suggests.

My first impression when riding the RR was of discomfort, as the seating position is pure G.P. racer.  The clip-on handlebars are slightly lower than the RK’s while the footpegs are mounted more rearward – that combined with the angled seat force the rider to assume a serious racing crouch.  That’s not a complaint, the whole purpose of the RR is to win races not cruise the main street. But while riding home from Suzuki South, along Adelaide’s bumpy Main South Road, the RR was telegraphing subtle messages that were all very positive.

Form and function.

Form and function.

Getting off the line takes a deft hand as the throttle is very light which makes it easy to feed in more revs than necessary, as the engine has minimal flywheel effect and responds instantly.  This is offset to a certain extent by the cable operated clutch which is smooth and progressive in its take up.  The tacho starts at 3000rpm, but the RR will take off with about 1000rpm less than this no problem, even though it runs a very high first gear.  Using the close ratio six-speed gearbox was a pleasure – even with only 800km of use.  The engine spins very freely with little vibration just a faint rumble at around 4000rpm in the higher gears that are felt through the footpegs and seat.  The RR will sit happily on 80kmh at just under 4000 revs in sixth gear and felt as though it would pull cleanly right up to its 13,000rpm redline.  In this sort of stop-start city riding the dual electrode spark, plugs showed their mettle, allowing the RR to pull away from traffic lights with only the occasional slight trace of a stumble.  I was quite surprised that the RR would tolerate such low revs and yet carburated so cleanly.

Another pleasant surprise was the suspension, which had been set-up by Jeff for fast road work yet handled the bumpy conditions well by giving a firm but compliant ride.  Two fingers were all that was required on the front brake as they are very powerful and combine with the riding position to make the rider feel sure the rear wheel is going to lift off the ground.  The fairing did quite an excellent job in the warm conditions too, managing to get the hot air from the engine away without scorching the rider. Some hot air is deflected by heat shielding under the fuel tank, however, onto the riders forearms when stopped at traffic lights.  I have to compliment Suzuki on the RR’s mirrors.  They are slightly convex, and an elongated oval in shape that gives a good view of the following traffic – not the riders elbows, nice one Suzuki.

It’s an understatement that the RR was not designed for the hostile environment of city commuting, but the Suzuki accredited itself surprisingly well (apart from the riding position), but to really get to know the RR better necessitates a more appropriate habitat.

The Adelaide Hills are crisscrossed with a great variety of scratchers roads, that vary from tight twisting turns to long sweeping curves – a natural place to head for with the RR.  In these conditions, the RR is in its element.  The Suzuki is so compact the rider can sense the centre of mass is just right, as the RR is so easy to flick into a corner, fast or slow, without any sign of top-heaviness that can affect an inline four in a double cradle loop frame.  The steering is razor sharp too, and it’s easy to place the Suzuki on the right line into a bend or change it mid-corner for that matter.

GSXR 750R in its natural habitat.

GSXR 750R in its natural habitat.

The engine is a real gem, it just loves to rev and gives such a linear power delivery that there is no real jump in performance.  On several occasion, when I managed to forget this was somebody else’s $20,000 motorcycle, my throttle hand got the better of me, and I ventured into this higher plateau of the RR’s performance.  Apart from the feeling that somebody had put the scenery on fast forward the RR handled up-rushing bends in exactly the same. way  A quick two-fingered squeeze of the powerful front disc brakes washed of excess speed, at the same time snicking down a couple of gears, tip the RR into the corner on the chosen line clip the apex and back on the power accelerating out.  No protests from the chassis or tyres just rapid progress.

On a couple of occasions, I did manage to get into a few corners a bit too hot and found that hauling on the brakes in a turn caused the RR to stand up and run wide, which on one particular off-camber corner caused the front-end to chatter.  However I put this down to a suspension set-up for someone else, and a too tentative response to the situation from yours truly.  High-speed stability was impressive also, the RR feeling rock steady in a straight line almost giving the impression of squatting down on the road as speed increased. The very effective fairing had a lot to do with this and made sustaining high speeds easy, helped no doubt by the tiny perspex screen which deflected the brunt of on-rushing air past the rider’s helmet with minimal buffeting.

Feeling at one with the exotic Suzuki GSXR 750R.

Feeling at one with the exotic Suzuki GSXR 750R.

Is it worth $20,000?  In my opinion, yes, it is that good. Suzuki has taken the evolutionary genes of their World Championship winning endurance racer and combined them with the DNA of their GSXR production model to create a racing thoroughbred.  But perhaps just as importantly it shows what good value for the money its slightly less race orientated stablemate the Suzuki GSX-R750K is.

Words Geoff Dawes (C) 1990. Photographs Geoff Dawes and Steve Frampton (C)1990. Published in Bike Australia May/June 1990.

Archives: Basic Instinct

Duncan Harrington and “Instinct”.

According to the Collins English Dictionary, “instinct” is an inborn intuitive power.  It’s also the name of the project that Duncan Harrington undertook in his final year as an Industrial Design student, and from which came the innovative motorcycle you see on these pages.  Duncan readily admits that it’s perhaps a misnomer when applied to his well thought out and engineered creation, but it does say something about his own intuition when it comes to questioning the primary and secondary safety of today’s motorcycle designs. But more of that later.

It was at the beginning of the year when 26-year-old Duncan proposed, as just one of his final year’s projects, to produce a motorcycle that would improve upon conventional chassis design and safety.  Unfortunately, the powers to be at the Underdale Campus of the University of South Australia needed a fair bit of persuasion, so the first half of the year was taken up with a research paper into roots and origins of motorcycle culture, which Duncan then used to help justify the project.  This was followed by a whole range of concept designs that were drawn up and presented before one was finally chosen.

Duncan then had to convince the University that he had the technical skills and know-how to complete the project in the time allowed.  Not an easy task with only six months left to do it in.  Fortunately, Duncan had completed an apprenticeship as a fitter and turner with CSR Softwoods in his hometown of Mt. Gambier before going to University and also had quite a few years experience restoring cars and motorcycles at home.

“Instinct oozes quality workmanship.

There was still, however, one more hurdle – finding the money to pay for the materials and components to construct the bike.  A sad farewell was said to Duncan’s bevel drive, square case 750SS Ducati,  when it was sold to help finance the project, followed later in the year by his rebuilt Suzuki Katana. Only the time factor remained, and as Duncan succinctly put it to me, ” I haven’t had a holiday all year!”

But after watching Duncan work meticulously on “Instinct” and listening to him talk about the ideas that went into the bike, I got the distinct impression that this was more than just a final year project. Which is quite understandable considering a large proportion of the bike had been handmade, polished and painted by Duncan.

The first impression of the bike is its high quality of workmanship, and a feeling of familiarity with its layout – the white chrome-moly steel trellis frame, single-sided swingarm and exhaust exiting under the seat is reminiscent of the Ducati 916. Even the exotic double wishbone front suspension has been tried before on other motorcycles like Kiwi John Britten’s V-twin, and the American Hossack (it’s also been experimented with by expatriate South Aussie Tony Foale who by coincidence is distantly related to Duncan).

The under engine fuel tank is also not new and has appeared on some racing motorcycles in the search for a lower centre of gravity – bikes like the Mead and Tompkinson endurance racer, and the French Elf endurance and 500cc G.P. racers.  But perhaps more importantly, it’s the sum of “Instincts” parts and the thinking behind them that makes this motorcycle special – particularly when it comes to selling new ideas to a very conservative bunch of consumers.

Twin wishbone front end is a primary safety feature.

Twin wishbone front end is a primary safety feature.

For example, the use of a more traditional engine design, in the shape of Honda’s venerable big single NSX 650cc motor, is not just merely to keep costs down.  Like most contemporary big singles, the dry-dumped Honda engine is designed to sit high in the frame and “Instinct” utilises this characteristic to enable the fuel tank to be easily mounted underneath it.  The chrome-moly trellis frame was another natural choice, as Duncan has designed it to be made in a kit form to suit most big single-cylinder engines that generally have their mounting point at the cylinder head and above or below the gearbox.  Just as important though, is that this type of frame offers good mounting points for the front wishbone suspension, and it’s also more visually acceptable in the eyes of purists.

The solid looking front “fork” is also made from chrome-moly steel and is encased in carbon-fibre for added torsional stiffness.  This is attached to the two alloy wishbones by a 14mm upper and 16mm lower ball joint that can be adjusted by thread and lock nut to vary the forks rake from a fairly standard 25 degrees to a very steep 18 degrees.  The front suspension also makes use of car type polyurethane bushes, while the double wishbones move on plain bearings in order to keep costs down.

The clip-on style handlebars and top yoke pivot in what looks like a conventional steering head (the lower part of which doubles as the top mounting point for the front shock absorber) and uses two rods with eyeball joints at both ends to attach the steering yoke to the fork. The bottom of the front shock absorber is angled out onto a mount at the front of the lower wishbone.

The shock absorber itself is an American car racing A.V.O. unit, with infinitely adjustable rebound and compression damping.  Duncan found the A.V.O. shock absorbers specification to be very good, and apart from being a lot cheaper than the “name” brand motorcycle type, it can also be purchased as a single unit with the added bonus of different rate springs being available for a mere $30.

The fuel tank is a carbon fibre, glass fibre and kevlar composite, wrapped around aluminium side panels and inner bulkheads that also act as baffles to stop the 18 litres of fuel sloshing around.  A reliable solid state Facet electric pump is mounted down by the petrol tank and takes care of the fuel supply to the carby.

The dummy tank and seat unit are made from injected high-density polystyrene that incorporates aluminium plates for strength at its mounting points and is wrapped in overlapping layers of carbon and glass fibre, again to add strength.  The whole thing pivots upwards at the front for good access to the battery, cylinder head and oil tank, although the oil tank cap is also easily accessible even with the dummy tank unit in place.

The seat and dummy fuel tank pivot forward for good access to the battery cylinder head and oil tank.

The seat and dummy fuel tank pivot forward for good access to the battery cylinder head and oil tank.

The seat itself is sculptured from a thin rubber base and covered in vinyl before being glued in place.  Another interesting feature of the dummy tank/seat unit is its single rear mounting point.  This is directly below the seat and uses urethane bush to help the thinly padded perch absorb some of the road shocks.  The paint job is also a local product called Two-pack Pro-Tech polyurethane and is used by HSV on the Commodore.

Duncan also made the stainless steel exhaust system, (apart from two one hundred and eighty-degree bands in the header pipes just after they exit the twin-port head, courtesy of Pace Maker Exhausts) and the aluminium muffler.  When viewed from the rear the muffler combines with the seats tail-piece to look uncannily like a snakes head!

Underseat exhaust is neat and tidy.

Underseat exhaust is neat and tidy.

As mentioned earlier the bike was designed to be built in a kit form and can use a variety of single cylinder engines, rear suspension, swing arms, wheels and brakes.  On Duncan’s prototype, these were cannibalised from a 400cc V-Four Honda NC 30.  A special thanks has to go to Alan Rigby Motorcycle Service in Mt. Gambier who supplied the wheels and tyres for just $300, including the cost of sending them to Adelaide.

This brings us to how Duncan Harrington’s design has improved primary and secondary safety over the latest motorcycle designs from the worlds largest manufacturers.  Well, not surprisingly, there first came an intensive study of motorcycle design, followed by extensive research into motorcycle accidents, which included material supplied by Adelaide Universities renowned Road Accident Research Unit.

To improve primary safety ,two things had to be accomplished that in general terms are contrary to each other – manoeuvrability and stability, which in most modern motorcycle designs is at best a compromise.  Duncan got his design off to a good start in the manoeuvrability stakes with a wheelbase of just 1380mm, helped by a light weight of 140kg with oil but no fuel.  This compares well with the likes of Suzuki’s 250cc RGV two-stroke (they also share similar power to weight ratio’s), but where “Instinct” shines is with its lower centre of gravity, thanks to the underslung fuel tank, and also by keeping the centre of mass as close to the middle of the bike as possible.

The other innovation that Duncan’s bike has over conventional designs is the improved stability achieved by taking advantage of mechanical characteristics of a twin-wishbone front suspension.  With a conventional telescopic front fork even normal braking will cause them to compress and effectively shorten the wheelbase.  Combine this with turning into a corner, which rolls the contact patch across the curved tread away from the centre crown of the tyre to the smaller diameter shoulder, and you reduce the wheelbase further to undermine stability even more.

"Instinct" looks good from any angle.

“Instinct” looks good from any angle.

When “Instinct’s” front suspension system is compressed under braking (or over bumps), the twin-wishbones move through an arc which slightly increases the wheelbase and also helps compensate for the decreasing diameter of the tyres when leant over in a corner.  Another safety benefit with the twin-wishbone front end is that it rides over bumps a lot better as there is none of the stiction associated with a conventional telescopic fork, and the inbuilt stability of the system makes it more difficult for large bumps and potholes in the road to unsettle the motorcycle.  Duncan is still in the process of getting “Instinct” road registered (mudguards, lights and a speedo are all that’s needed), but has managed to put in some exploratory laps at the Mallala race track, and these have more than confirmed his faith in the design.

Just as impressive though are the secondary safety features of Duncan’s design.  From his research, he found that the front end t-bone was one of the most common accidents happening to motorcyclists and that there was a marked increase in the number of injuries to the lower abdominal region of the rider, whom according to the statistics are mainly males under 25.  Not good for the family jewels.  It was discovered that the increasing size of air boxes on motorcycles to help manufacturers meet noise pollution and performance requirements, were also increasing the height and width of fuel tanks with the aforementioned consequences.

By using an underslung fuel tank on “Instinct”, Duncan was able to go “organic” with the design of the dummy tank and seat unit, allowing it to be made lower in height and narrower in width as it is purely for styling.  The next problem our poor crash victim faces once he makes it past the fuel tank are the handlebars.  These have a nasty habit of shattering parts of the lower leg, which most definitely is not something to look forward to while holding onto one’s crotch.

Shear pins are used to secure the handlebars in place.

Shear pins are used to secure the handlebars in place.

Duncan has solved this problem by using shear pins through the steering yoke to lock “Instinct’s” handlebars in place.  As the name suggests the pins will shear when hit with a reasonable force, causing the handlebars to pivot forward and away, thereby saving the rider from a more serious leg injury.  While we’re on the subject of lower legs, Duncan has also made the foot pegs solid and mounted them at bumper bar height as he believes this offers better protection from errant car drivers than the swivel up type, which are more likely to cause the riders lower leg to be squashed in an accident.

Perhaps more than anything Duncan’s design project highlights how almost laughingly obvious some of the solutions are to the inherent problems built into the traditional motorcycle, and just as equally, how conservative motorcyclists are when it comes to accepting new technology.  Ask anyone at Yamaha involved with the GTS 1000.  Even the successful BMW R1100RS incorporates a sliding fork un its single wishbone front-end, not only as a necessary part of the design but also, no doubt, so as not to scare away too many traditionalists.

Will weever see it in production.

Will we ever see it in production?

In Duncan’s case, he has taken a step backwards to go forward by basing his design on a simple, reliable, single cylinder engine, and of course, a tubular steel frame to help package his concepts.  Although “Instinct” is designed to be built in a kit form, it, unfortunately, is beyond Duncan’s means to manufacture and market the design in any realistic numbers.  Let’s just hope there’s a manufacturer out there with enough foresight to prevent such an interesting and practical design becoming more than just another one off special.

Words and photographs Geoff Dawes (c) 1994. Published in Streetbike  April/May 1995.

Archives: Kawasaki Z1 Super 4

The Z1 had a majestic presence

When Honda unveiled the CB750 at the Tokyo Motor Show in 1968, it immediately captured the imagination of the motorcycling public.  It would become the first mass-produced, large capacity, across the frame, O.H.C. four-cylinder motorcycle.  And it also boasted another motorcycling first, a front disc brake.  But just as importantly, it would be affordable for the general public to buy.

The CB750 was a technological tour de force that set a new benchmark for the other manufacturers to match.  When it hit the showroom floor a year later, it set a precedent in large capacity motorcycle design that has lasted to this day.

But if the Honda “four” captured the public’s imagination, then the Kawasaki Z1 super4 stole it.

Conceived in 1967 after intensive research by Japanese-American Sam Tanegashima into the needs of the world’s most important motorcycle market, the United States, Kawasaki set its design parameters for a new large capacity motorcycle.  Its heart was to be a compact D.O.H.C. 750cc four-cylinder engine that placed emphasis on lower exhaust emissions and running noise.  The project had reached wooden mock-up stage by September of 1968 only to be still-born when Honda revealed the similar in concept CB750.  But although this blow initially shelved the project, code-named “New York Steak”, it also proved useful to Kawasaki.  They could now gauge market reaction to the big Honda, and in 1969 another intensive survey of the U.S. was undertaken.

Z1 final mockup courtesy Kawasaki Australia

Later that year the final decision was made.  The small team involved in the project, Mr Inamura and Mr Togashi, (chief engineers for the engine and chassis) and Mr Tada, (chief designer) were told “New York Steak” would go ahead.  But Kawasaki’s re-evaluation had concluded that the engine capacity should be 900cc.  This created a new niche in the large capacity motorcycle market, and Kawasaki would regain the mantle, formerly held by its W series 650cc twin, as the largest capacity motorcycle on offer from Japan.

The real challenge for the engineering and design team, however, was to meet Kawasaki’s ultimatum to have the new bike ready for final testing within 24 months.  Although a lot of groundwork had already been done, with over $800,000 invested in development costs for the 750cc version, the timetable was still a tough one.

In the Japanese spring of 1970 the first prototype hit the demanding Yatabe test course, and in the hands of its American test rider lapped at an incredible average speed of 200kph.  There were problems though, the crankcase breather system let oil out instead of keeping it in, and piston crowns succumbed to the intense heat of combustion.  But the issues were rectified, and rewarded, with one prototype recording 95bhp and a top speed run of 225kph.

Z1 final prototype (curtesy Kawasaki Australia)

Z1 final prototype (courtesy Kawasaki Australia)

In January 1972 pre-productions models were shipped to Los Angeles for testing on public roads.  On a round trip to Daytona in Florida, they covered over 20,000km which included endurance testing on road race circuits.  Apart from some minor chain and tyre problems, they proved the reliability of Kawasaki’s design.  Not content with this, Kawasaki returned to the States three months later for more extensive tests.   The results even surpassed Kawasaki’s own expectations.

It was time to go public, and in June 1972 the worlds motorcycle press were invited to Japan by Kawasaki.  The Z1 super4 was officially announced and opinions of the motorcycle, both good and bad, were eagerly sought – if Kawasaki were to beat Honda at their own game everything had to be right.  By August the production lines were readied, now it was up to the marketing men.

Press release from Mr. Yamada (courtesy Kawasaki Australia)

Press release from Mr Yamada (courtesy Kawasaki Australia)

In September 1972 the Z1 was launched at the Cologne Motor Show while in Japan the production lines started to roll, building a conservative 1500 units per month. The Kawasaki design team held their collective breath while they waited to gauge market reaction to the new model.  There was no need to worry, the Z1 super4 took the show by storm, as it did the other European shows that followed.  By 1975 Kawasaki would be building 5000 units per month.

It was the demands of the tough American market that had fathered the Z1, and something special was in store to underline the muscle-bound roadsters capabilities.  In March 1973 a team of riders, mechanics and officials, arrived at Daytona Motor Speedway.  Their aim, to set new speed and endurance records for a production motorcycle.  Three days later they had established 46 F.I.M. and A.M.A. records including a new 24-hour record for a production motorcycle of 176.412km/h.

Paul Cawthorne on the Bolton's Z1

Paul Cawthorne on the Bolton’s Kawasaki Z1.

Later that year, at its first attempt, the Kawasaki Z1 came second, fourth and fifth in the gruelling Bol d’Or 24 hour endurance race, while in Australia, after an epic solo ride, Kenny Blake won the prestigious Castrol Six-Hour production race.  The opening chapter of a legend had been written.

Z1 Technical File

“You can design the most beautiful motorcycle in the world, but if it doesn’t have the right engine, there’s no way you can make a complete package.  Therefore, in all our bike development, the first consideration is the engine.” – Mr Inamura Chief Engineer Four-Stroke Engines, responsible for the Z1.

In the four years before the launch of the Z1, the Honda CB750 had established itself as the yardstick that other large capacity “sports tourers” were judged by.  But although the contemporary Honda engine set the trend for an across-the-frame four, the technical specification between it and the Z1 was poles apart.

The CB750 boasted a single overhead camshaft with the valves actuated by rocker arms and adjusted by screw and lock nut.  It had a bore and stroke of 61mm x 63mm with two-piece connecting rods that bolted together on a forged one-piece crankshaft which was supported by five plain main bearings.  The primary drive was by dual sprockets and two single row chains, while the engine oil was supplied from a separate oil tank mounted under the frames side cover to a “dry” sump.  It produced a maximum of 67bhp at 8,000rpm and 6.1kg-m of torque at 7,000rpm.

Bullet proof.


The Z1, on the other hand, featured twin overhead camshafts that operated directly onto the valve via a “bucket” which used different thickness metal shims located on the top of it to adjust valve clearance.  It had a “square” bore and stroke of 66mm x 66mm, while the crankshaft was a pressed up five-piece unit that allowed the use of one-piece connecting rods.  The crankshaft was supported by six caged roller main bearings that required only low oil pressure to spin freely.  The lubrication system was by wet sump, while the primary drive used a straight cut gear on the crankshaft web and turned directly on the clutch.  The Z1 produced a whopping 82bhp at 8,500rpm and 7.5kg-m at 7000rpm.  It was also a very compact design – over 7.6cm narrower than the Honda.

Both engines were sound designs and relatively under-stressed, and both responded well to tuning, but it was the D.O.H.C. design of the big Kawasaki that had the edge.  During Kawasaki’s record-breaking blitz at Daytona, a stock Z1 with slightly modified camshafts and cylinder head, different carburettors and a four into one exhaust system, produced 105bhp at 10,500rpm.  French Canadian road racer, Yvonne Du Hamel, used this bike (fitted with full fairing, race seat, clip-ons and slicks) to set a new closed course flying one lap record of 257.9km/h.  Its top speed on the straight was 280km/h!

Factory dynometer readings for the Z1 9courtesy Kawasaki Australia0

Factory dynometer readings for the Z1 (courtesy Kawasaki Australia)

But the outright performance was not the only consideration that had to be made by the engine team.  The tightening pollution regulations in the US, particularly in California, required contemplation.  Mr Inamura and his group took a leaf out of the auto industries book and came up with PCV, Positive Crankcase Ventilation.  This was a means of recirculating “blow-by gasses”, mainly unburnt fuel that passes the piston rings and enters the crankcase.  These gasses can contaminate engine oil and were usually vented by a crankcase breather into the atmosphere.  The PVC valve allowed the gasses to be separated and vented from the crankcase back into the airbox to be re-burned, bringing about a claimed 40% reduction in hydrocarbon emissions.

Another feature of the engine design was hardened valve seats and phosphor bronze valve guides, which allowed the Z1 to run on unleaded fuel.  The valve guides, however, were found to wear rapidly enough for the factory to replace them in later models with iron items.

The Z1 engine quickly became the favourite of performance tuners around the world and established itself as the engine to beat.  From endurance racing to drag racing the Z1 engine proved almost unbreakable.  Perhaps the greatest form of flattery is imitation, a compliment paid by Suzuki when it introduced its first large capacity multi-cylinder four-stroke street bike with the GS range that featured an engine configuration almost identical to the Z1.


In the early seventies, Australia was in the grip of the worldwide boom in motorcycle sales.  Two-wheeled transport became so popular that car dealers took on motorcycle franchises as a sideline to their passenger car sales.  It was into this buoyant environment that Kawasaki launched its new “super4”, and with their first shot, they hit the bullseye.

Author and his 1973 Z1A.

Author and his 1973 Z1A.

Never had a motorcycle been more anticipated in Australia than the Z1.  The American magazines were full of superlatives about the big new muscle bike before it arrived on Australian shores, and when it did, it received the same kind of acclaim from the local press.  There were some reservations about the big Kawasaki’s handling under duress, but remember, this was the most powerful production motorcycle in the world!  Not only could it cut the standing 400 metres in 12 seconds flat, but it had an amazing (for 1972) top speed of 217km/h.

Bolton’s, the South Australian distributor for Kawasaki, displayed the Z1 in the window of its Greenhill Road showroom with a sign that was in keeping with factory publicity, and boldly stated, “for experienced riders only”.  That sign did little to deter would-be purchasers, if anything, it just underlined the performance of the big Kawasaki.

It should be remembered though, that in 1972 it was not unusual for Japanese motorcycles to have some “interesting” handling traits.  Most Oriental motorcycles were fitted with home brand tyres that quickly qualified for the title “rim protectors” as they were good for little else.  Japanese suspension manufacturers had yet to master the art of effective compression and rebound damping, especially on the new breed of heavy big bore motorcycles coming from the land of the rising sun.


A superbike superstar.

All of the above though was pretty academic.  It was the outright performance of these new machines that were all important and the engine technology that provided it.  Plus a build quality, finish and reliability that made the minuses much easier to live with. And there was nothing quite like the sound of a Honda CB750 with all four baffles out, that is until the Z1 came along…

The big Kawasaki exasperated problems with the chassis technology of the day, simply because it was heavy (209kg dry) and so powerful.  It should be noted that even the European tyre manufacturers were not prepared for the Z1 and it soon started a race to produce more suitable rubber.  English tyre manufacturer, Avon, was one of the first with their “Roadrunner” range and quickly developed a presence in production racing, which was by then dominated by the Z1.

For the average owner to improve a Z1, it merely meant replacing the standard rubber for a set of Avon’s, trading the original shocks for some Koni’s, plus experimenting with different front fork oil. Fitting an adjustable Kawasaki steering damper also helped.  All the above made an improvement and it was possible to use up more of the Kawasaki’s good ground clearance during a Sunday blast.  But somewhere along the way, the Z1 would always remind you that it was still one big heavy motorcycle.

Kawasaki’s publicity called the Z1 super4 a super sports tourer, and it was ably suited to that role.  With two-up and luggage onboard the bike could eat up the miles effortlessly, with 4500rpm in top equating to 110km/h and returning around 6 litres per 100km fuel consumption.  The Z1 did suffer some shortcomings – the standard handlebars were too high and wide, making the rider a wind sock at speed.  At cruising speeds secondary engine vibration could be felt, although on its own it was not really a problem, but combined with the hard plastic hand-grips, it became hand numbing after a while.  Also, the seat was too narrow at the front and a bit too firm over long distances.

Another gripe was the front disk brake.  It had a high content of the stainless steel, which prevented it from rusting – unfortunately when it rained and the brakes were applied nothing much happened!  A makeshift solution was to drill holes in the disk which helped dissipate the water more quickly.  It was a problem that sent Kawasaki on a search for better brake pad material and is responsible for the superior sintered metal pads we enjoy today.

Twin disk brake was an option.

Twin disk brake was an option.

General maintenance of the big Kawasaki was pretty straightforward and well within reach of the home mechanic.  A relatively inexpensive special tool was required to allow shims to be changed for valve clearance, and a set of vacuum gauges made synchronising the carburettors easier.  Unlike the CB750, Kawasaki had designed the Z1 so the cylinder head and barrels could be removed with the engine still in the frame, in fact, it was only in the rare occurrence of the crankshaft or gearbox needing attention that the engine had to be removed.

Although the Z1 was fitted with the heaviest duty chain available (630), an adjustable automatic chain oiler was fitted to help extend its life.  An oil tank under the left side cover fed a plunger type oil pump that ran off the gearbox output shaft and lubricated the chain from small holes above the gearbox sprocket.  It was fitted to the Z1-Z1A before a lower maintenance Hatta o-ring chain became standard on the Z1B.

The Z1 was a good looking machine, and it was interesting to read the policy notes of Mr Tada, chief designer of the Z1, as they sum up the appeal of the Kawasaki at the time.  They read as follows ” a: a gallant and inspiring leader of Kawasaki’s street line, b: originality in styling, to be different to any other bike on the street (anti-Honda styling), c: a better look and higher quality than those of other competitive machines”.

The Z1 had a majestic presence about it and some good detail design innovations.  The faired automotive type mirrors were a  first, and not only looked good but functioned well.  The bullet-shaped gauges blended well with the overall styling and featured yet another first – a “dashboard” for the warning lights that also incorporated the ignition switch.  Pretty hot stuff in 1972.  Also, the reflectors fitted to the front fork and rear shockers were not just for style – side on visibility of motorcycles at night was of some concern in the United States, so reflectors were a practical response.

The Z1 incorporated a first in having the ignition an "idiot lights" between the gauges.

The Z1 incorporated a first in having the ignition and “idiot lights” between the gauges.

It may be hard to imagine now, with all the Japanese manufacturers offering ballistic big bore models as front-line weapons in the battle for street bike supremacy, but from the Z1 of 1972, through to Z900 of 1976, the Kawasaki reigned supreme as the all-round performance King of production motorcycles.  In 1967 when Japanese-American Sam Tanegashima researched the kind of large capacity motorcycle that Americans would buy, he envisioned a super cruiser, a machine that was equally at home in city traffic, or cruising lazily down country roads, to running flat out on America’s superhighways. A motorcycle that could stand proudly alongside the legendary Vincent HRD of yesteryear.  From those of us that owned a Z1, Sam, you got it right.

Words and photographs Geoff Dawes. (C) 1997. Photograph Viv Dawes (C) 1984. Published April 1998 in Two Wheels