Japan’s first literbike brought thrilling performance to everyday riders

Kawasaki Heavy Industries, Ltd. made an indelible mark on the world motorcycle scene back in 1972 with the unveiling of its 1973 Z1 model. The Z1 broke new ground as the first Japanese bike with a transverse-mount four-banger, and it’s widely recognized as the island nation’s first literbike with a 903 cc engine and thrilling performance for everyday riders.

  • 1973 Kawasaki Z1
  • Year:
    1973
  • Make:
  • Model:
  • Engine:
    inline-4
  • Displacement:
    903 cc
  • Top Speed:
    130 mph
  • Price:
    1895
  • Price:

Kawasaki Z1 History

1973 Kawasaki Z1
- image 893313
1973 Kawasaki Z1
- image 893317

The motorcycle field at the time had been shaped, first by Honda’s 1968 CB750, then by Kawi’s own two-cycle triple – the reknowned Mach III – in 1969. Those two bikes set the stage for the emergence of the Z1. This heralded the age of the Universal Japanese Motorcycle (UJM) and also marked the potential competition that the burgeoning Japanese motorcycle market would pose to the status quo.

American and European manufacturers were all well established, but the Z1 would represent a very real threat from the East, mainly due to its 900 Super Four engine and affordable price tag. Originally, the engine was slated to be smaller, but Honda’s “Dream” pressured upstart manufacturer Kawasaki to punch out the engine and up the displacement and performance.

While the public release of the Z1 was a momentous occasion, the bike had spent the previous racing season proving itself with a pair of world records at the Daytona track for endurance. It has long been said that if you want to sell bikes, you have to win races, and that certainly held true for Kawasaki’s Z1 back in the early Seventies.

Kawasaki Z1 Design

  • Quintessential UJM
  • Mid-mount controls
  • Upright seating position
1973 Kawasaki Z1
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1973 Kawasaki Z1
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1973 Kawasaki Z1
- image 893316

Folks, the Z1 is the quintessential UJM cruiser with a full-cradle frame and transverse, four-stroke, four-banger engine. Chrome and polished aluminum feature prominently across the design, starting with the bright steel in the laced rims and chrome front fender that rides between polished fork sliders and chrome inner fork tubes.

The hard-and-shiny finish continues into the tripletree and cyclops headlight housing with a chrome handlebar to finish out the front end. The round mirrors, along with their standoffs, provide a bit of contrast with a blackout paintjob.

A four-gallon teardrop tank establishes a gentle drop in the flyline to the pattern-stitched bench seat. Stock passenger footpegs and a grabstrap join with a chrome J.C. rail to complete the pillion’s accommodations.

A straight rear fender carries the taillight and plateholder underneath, and the latter doubles as a mudguard extension to contain the spray from the rear hoop. Mid-mount foot controls and mid-rise handlebars put the pilot in a comfortable upright riding position, another endearing hallmark of the UJM genre.

While the marque has recently released a tribute bike, the Z900RS, it departed from the original with widespread blackout paint in the place of chrome, and modern inverted forks ahead of a liquid-cooled engine. The sheet metal and profile, however, are very similar to the original.

Kawasaki Z1 Chassis

  • RWU non-adjustable front forks
  • Spring-preload adjustable rear suspension
  • Laced wheels
1973 Kawasaki Z1
- image 893325

Tubular steel members make up the full-duplex, double-downtube/double-cradle frame with a yoke-style swingarm to finish off the main structure. As was typical for the time, the front forks are right-way-up and non-adjustable, and the dual coil-over shocks out back have the obligatory spring-preload adjustment as the only suspension adjustment.

At 59-inches long, the wheelbase places the Z1 in the full-size cruiser sub-category. Laced wheels round out the rolling chassis, and while the stock machine rolled with a 290 mm hydraulic disc brake up front and a 200 mm drum out back, a second disc-and-caliper combo was available as an accessory item. Compare that to the all-around disc brakes, stock dual front discs, and ABS feature on the modern version, as well as the inverted forks and hidden rear monoshock.

Frame: tubular steel, double cradle
Front Suspension: 36mm Telescopic forks
Rear Suspension: Dual shock, 5-way preload adjustment
Front Brakes: Single 296 mm disc, 2-piston caliper
Rear Brakes: 200 mm drum
Front Tire: 3.25-19 73-75
Rear Tire: 4.00-18 73-75

Kawasaki Z1 Drivetrain

  • Inline 4-cylinder engine
  • 903 cc displacement
  • push-button and kick starter
  • 81 hp @ 8, 500 rpm
  • 54 lb-ft @ 7,000 rpm
1973 Kawasaki Z1
- image 893322
1973 Kawasaki Z1
- image 893326
1973 Kawasaki Z1
- image 893314

Originally, the Z1 was to have a 750 cc mill, but Honda’s CB750 forced Kawi to make some adjustments. In the end, the air-cooled engine wound up with both a 66 mm bore and stroke for a square layout and a 903.2 cc total displacement. It rolled with both a kicker and push-button starter.

Babbitt (plain) bearings supported the over-head cams while roller bearings were used in the bottom end as the latter were considered superior for the high loads on the crankshaft. A bank of four carburetors controlled the induction, which made it more difficult to tune than the American and British twins, but that’s the trade off for the power that the inline-four brought to the table.

What kind of power? Well, the mill produced 81 horsepower at 8,500 rpm backed up by 54.2 pound-feet of torque. A five-speed transmission and chain-type final drive turned out a top speed in the 130-to-132 mph range. This made it faster than its occidental counterparts, which is yet another factor that endeared the Z1 to the masses and helped to catapult Japan into the frontrunners of worldwide motorcycle performance – a position it still enjoys to this day. The modern-day tribute is understandably more modern with a 948 cc engine, slipper-style clutch and traction control, plus it’s a bit gruntier with a claimed 72.3 pound-feet of torque at 6,500 rpm.

Engine: Air-cooled DOHC inline-four, 2 valves per cylinder
Displacement: 903 cc
Bore x Stroke: 66 mm x 66 mm
Compression ratio: 8.5:1
Horsepower: 81.94 hp (61.1 KW) @ 8, 500 rpm
Torque: 53.84 lb-ft (73.0 Nm) @ 7,000 rpm
Fuel System: 4x Mikuni VM 28 mm carburetors
Transmission: 5-Speed Return Shift
Final Drive: Chain: 630x92
Front Sprocket: 15T
Rear Sprocket: 35T

Kawasaki Z1 Pricing

1973 Kawasaki Z1
- image 893324

The 1973 Z1 originally rolled for $1,895 in the U.S. market, which placed it decidedly on the affordable end of the spectrum, especially compared to the Harley-Davidson Sportster and MV Agusta twins of the era.

Kawasaki Z1 Competitors

1973 Kawasaki Z1
- image 893318
1973 Kawasaki Z1
- image 893313
1973 Kawasaki Z1
- image 893314

Honda’s CB750 is one of the most obvious competitors, in both design and proximity, but the world stage was awash with comparable bikes. The Brits – Triumph, Norton, and BSA – had models in the 750 cc bracket, though they were of the parallel-twin variety that was common at the time.

Harley-Davidson’s Sportster ran a V-twin; of course it did since it came from The MoCo in Milwaukee, but the 1,000 cc Sporties couldn’t match the horsepower from the inline four. Torque, however, was a different story, but that’s to be expected from a V-twin. MV Agusta had transverse four-banger too, but priced at $5,000 (in 1973!) it was a premium machine that would appeal to only the most well heeled rider base whereas the Kawasaki was priced more for the everyrider.

He Said

“Definitely a significant model in the evolution of motor bikes, and the company as a whole. This attractive sled would also be used as a platform for homemade café racers to further endear itself to Western riders and the Japanese buyers alike. It evokes a certain sense of nostalgia in me, ’cause when I was a young lad this is what a Japanese motorcycle looked like so if you’re wondering if I’d ride it, the answer is ’hell yeah!’”

She Said

My wife and fellow motorcycle writer, Allyn Hinton, says, “When the Kawasaki Z1 was released in the U.S., it quickly became a legend in its own time. It was faster and so much sexier than anything else out there. Every hourly speed record in the U.S. was smashed by the Z1, so it instantly became entrenched in our bike culture. The modern Z900 is a fitting tribute to its early ancestor in looks and performance.”

Kawasaki Z1 Specifications

Engine & Drivetrain:
Engine: Air-cooled DOHC inline-four, 2 valves per cylinder
Displacement: 903 cc
Bore x Stroke: 66 mm x 66 mm
Compression ratio: 8.5:1
Horsepower: 81.94 hp (61.1 KW) @ 8, 500 rpm
Torque: 53.84 lb-ft (73.0 Nm) @ 7,000 rpm
Fuel System: 4x Mikuni VM 28 mm carburetors
Spark Plug: NGK B8ES 73-75
Battery: YUASA 12N14-3A 73-75
Transmission: 5-Speed Return Shift
Final Drive: Chain: 630x92
Front Sprocket: 15T
Rear Sprocket: 35T
Chassis:
Frame: tubular steel, double cradle
Front Suspension: 36mm Telescopic forks
Rear Suspension: Dual shock, 5-way preload adjustment
Front Brakes: Single 296 mm disc, 2-piston caliper
Rear Brakes: 200 mm drum
Front Tire: 3.25-19 73-75
Rear Tire: 4.00-18 73-75
Dimensions & Capacities:
Wheelbase: 59.0 in (1,498.6 mm)
Seat Height: 32.0 in. (812.8 mm)
Dry Weight: 507 lbs (230 kg)
Curb Weight: 546 lbs (247.6 kg)
Fuel Capacity: 4.7 gal (18 Liters)
Fuel Consumption: 45 mpg (average)
Top Speed: 130 mph

Further Reading

Kawasaki

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TJ Hinton
T.J got an early start from his father and other family members who owned and rode motorcycles, and by helping with various mechanical repairs throughout childhood. That planted a seed that grew into a well-rounded appreciation of all things mechanical, and eventually, into a formal education of same. Though primarily a Harley rider, he has an appreciation for all sorts of bikes and doesn't discriminate against any particular brand or region of origin. He currently holds an Associate's degree in applied mechanical science from his time at the M.M.I.  Read More
About the author

All images featured on this website are copyrighted to their respective rightful owners. No infringement is intended. Image Source: wheelsage.org, kawasaki.com

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