|Manufacturer||Kawasaki Heavy Industries, Ltd.|
|Also called||Kawasaki 900 Super Four |
|Production||1972–1975; 85,000 units (est.) |
|Successor||Kawasaki Z900 |
|Engine||DOHC 903 cm3 (55.1 cu in) air-cooled, inline-four|
|Bore / stroke||66 mm × 66 mm (2.6 in × 2.6 in)|
|Top speed||130–132 mph (209–212 km/h) |
|Power||82 PS (81 hp) at 8500 rpm |
|Torque||54.2 lb⋅ft (73.5 N⋅m) at 8500 rpm |
|Frame type||Full duplex cradle|
|Suspension||F: Telescopic, R: Swing arm|
|Brakes||F: 11.5 in (290 mm) disk (optional 2nd disk)|
R: 7.9 in (200 mm) drum
|Tires||F: 3.25-19, R: 4.00-18|
|Wheelbase||1,490 mm (59 in)|
|Dimensions||L: 2,200 mm (87 in)|
W: 685 mm (27.0 in)
H: 1,170 mm (46 in)
|Weight||510 lb (230 kg)  (dry)|
542 lb (246 kg)  (wet)
|Fuel capacity||18 L (4.0 imp gal; 4.8 US gal)|
The Kawasaki Z1 is a four-cylinder, air-cooled, double-overhead camshaft, carbureted, chain-drive motorcycle introduced in 1972 by Kawasaki. Following the introduction of Honda's CB750 in 1968, the Z1 helped popularize the in-line, across-the-frame four-cylinder, a format that became known as the Universal Japanese Motorcycle or UJM.
The Z1 was noted for being the first large-capacity Japanese four-cylinder motorcycle to use the double-overhead-camshaft system on a production motorcycle. When it was introduced, only the MV Agusta 750 S used this system; it was a very expensive limited-production machine, as opposed to the Kawasaki which was less than half the price.
The Kawasaki Z1 was developed under the project name "New York Steak". In the late 1960s Kawasaki, already an established manufacturer of two-stroke motorcycles, had begun prototyping a 750 cc four-cylinder four-stroke sports motorcycle working with McFarlane Design in 1969 to develop the bike's overall appearance. When Honda introduced the CB750 to the market first, Kawasaki postponed the Z1's release until its displacement could be increased to 903 cc and the motorcycle could be marketed in the 1000cc-class.
Z1 production began in 1972 as the most powerful Japanese 4-cylinder 4-stroke ever marketed.
In 1972, the Z1 set the world FIM and AMA record for 24-hour endurance on the banked Daytona racetrack, recording 2,631 miles at an average speed of 109.64 mph. Writing in 1976, LJK Setright commented that this record was only 0.36% faster than the previous figure set in 1961 at Montlhéry, France, by a team using a modified BMW R69S, particularly the engine. Also at this time at Daytona a one-off Z1 ridden by Yvon Duhamel that was tuned by Yoshimura set a one-lap record of 160.288 mph. Setright commented that this achievement, using a 100-bhp output engine, was reflective of the progress made in a dozen years.
The Z1 had full instrumentation and an electric start, produced 82 bhp and had a maximum speed of 130 mph to 132 mph (210 km/hr). It met with positive reviews from the motorcycle press, who praised its smoothness, damped vibration, easy starting (kick-start and electric were both fitted), straight-line stability and linear acceleration. Steering was accurate and the bike handled well, but testers said the rear tire, chain and rear shocks all wore out quickly.
The Z1 was awarded the MCN 'Machine of the Year' accolade each year from 1973 to 1976 (an award resulting from a readers' opinion-poll run by UK weekly publication Motorcycle News) The Society of Automotive Engineers of Japan (in Japanese) includes the 1972 Z1 as one of their 240 Landmarks of Japanese Automotive Technology.
The basic design of the Z1 remained relatively unchanged until 1975, when the 903 cc "Z1-B" was introduced, with changes including increased power output, improved suspension, and a stiffer frame. The automatic chain oiler was deleted, the styling was revised – essentially paint scheme and side-panel nomenclature – and the braking was improved.
In 1976 the Z1 was replaced by the Kawasaki KZ900 in the U.S. and Z900 in other markets. This was succeeded by the 1977 Kawasaki Kz1000 ("Z1000") and Kawasaki Z1000 Z1-R, and in 1984 by the Kawasaki Z1100R.
In 1983, Kawasaki won back the crown of the fastest production bike with the Kawasaki GPZ900R which had some other references to its predecessor like the model designation code ZX900, four cylinders and 900 ccm.
In 2018 Kawasaki released the Z900RS. This bike is a tribute to the original Z-1, but with such modern features as water cooling, fuel injection, a 6-speed transmission, upside-down front forks, mono-shock rear suspension, ABS brakes, and traction control.
- "Kawasaki 900 Super Four". 240 Landmarks of Japanese Automotive Technology. Society of Automotive Engineers of Japan, Inc. Retrieved 6 November 2013.
Journalists and riders called it the king of motorcycles, and it gained a reputation as a super sport model all over the world. The Super Four boasted high performance and quality. This best-selling motorcycle won many prizes around the world within only six months of its release.
- Siegal, Margie. "1973 Kawasaki Z1: King of the Road". Motorcycle Classics May/June 2006. Retrieved 10 December 2012.
- Ker, Rod (29 September 2008). "Kawasaki Z1: remembrance of things fast". The Telegraph. Archived from the original on 2022-01-12. Retrieved 6 November 2013.
While I don't have a clue what I was doing when Kennedy was shot, I can clearly remember the first time I saw a Kawasaki Z1. In 1974, this four-cylinder, 903cc, 81bhp, 132mph projectile was the fastest, most glamorous thing on two wheels. Only a handful had been sold in Britain, and only the lucky few had even seen one.
- Newland, Martin (5 May 2004). "Retro rocket". The Telegraph. Archived from the original on 2022-01-12. Retrieved 6 November 2013.
The 1973 Kawazaki Z1 was the world's first superbike and its spiritual successor, the Z1000, relies on the same stripped-down looks and raw, steady power for its appeal. It's the ideal big boy's toy…
- Walker, Mick (2 October 2006). Motorcycle: Evolution, Design, Passion. The Johns Hopkins University Press. p. 150. ISBN 978-0-8018-8530-3.
- Brown, Roland (2006), The Ultimate History of Fast Motorcycles, Bath, UK: Parragon, pp. 214–215, ISBN 1-4054-7303-7
- Williams, Greg. "Son of Z1: The 1976 Kawasaki Z900". Motorcycle Classics September/October 2012. Motorcycle Classics. Retrieved 10 December 2012.
- John L. Stein (1 August 2010). "Then & Now: Kawasaki Z1000 vs. Z1". Motorcyclist. Source Interlink Media. Retrieved 6 November 2013.
During its development, the 1973 Kawasaki Z1 was codenamed New York Steak. And it was just that: 23 percent larger than Honda's benchmark 750cc Four, it busted open the fledgling superbike ranks and would soon make its impact in racing, too. Blasphemously heavy at 542 lbs. wet, the Z1 did everything to excess, from its audacious 903cc DOHC four-cylinder engine to its roomy cockpit, enormous linkless chain with proprietary oil pump, and quartet of chrome-plated megaphones.
- Melling, Frank (27 July 2007). "Memorable Motorcycle Kawasaki Z1". Motorcycle USA. Retrieved 6 November 2013.
It's time to correct one of the popular myths which is becoming ever more prevalent in the motorcycling world. Thus: 'When Honda launched its 750 '4' in 1968, the biking world fell on its knees and worshipped the new arrival.'
- Kuhn, Fran (24 February 2009). "Kawasaki 903 Z1 - Bikes of the 70's". Motorcyclist. Source Interlink Media. Retrieved 6 November 2013.
By now you must've already heard the story of how the Z1--code-named 'New York Steak' for some ridiculous reason or other by Kawasaki--was originally intended to be a 750, and of how Kawasaki brass nearly suffered a corporate coronary when Honda introduced its own 750cc four-cylinder in late 1968. Kawasaki, cornered, had no choice but to make the Z1 even bigger and stronger and tricker than the mighty CB750.
- "40 years of Kawasaki's 'Z' sleds". Independent Online. Independent Newspapers (Pty) Limited. 5 June 2012. Retrieved 6 November 2013.
…the DNA of the 1972 Z1 is still clearly discernable in the Kawasaki's current litre-class musclebike, the Z1000.
- "The Kawasaki Prototype". Motorcycle Classics September/October 2006. Retrieved 10 December 2012.
- Motorcycles, LJK Setright, 1976, pp.138-143 Weidenfeld & Nicolson London. Accessed 29 June 2019
- Boehm, Mitch (May 5, 2016). "The Legendary Kawasaki Z1". Motorcyclist. Retrieved June 1, 2016.
- "Kawasaki official site". Retrieved 2013-04-06.
- Wagar, Ivan. Kawasaki's 900cc New York Steak, Cycle World October 1972.
- Kawasaki 900 Z-1 Road Test, Cycle World March 1973.
- David Marsden, Original Kawasaki Z1, Z900 and KZ900: The Restorer's Guide to All Aircooled 900cc Models 1972-1976, hardcover 1 June 2011.