Kawasaki To Reproduce Cylinder Heads For ’70s Z1s

[Hugh Janus]

Kawasaki announced that it will reproduce the cylinder heads for 1970s Z1 motorcycles. (Kawasaki/)

Kawasaki’s 903-cc Z1, introduced in the US in 1973, was a revolution in defining what a motorcycle could be. In a world in which 650 was big (all those 1960s British twins) and 750 was huge (Triumph’s Trident Triple, Norton’s Commando, and Honda’s CB750 Four), the Z1 was an all-new animal. People had to have it then, and they still revere it today.

Evolving in the hands of builders in AMA’s early production classes, this bike was the single greatest cause of the Superbike revolution—the idea that there could and should be an all-but-unlimited roadracing class for truly production-based machines. Who can forget the great rides and championships won by Eddie Lawson on Rob Muzzy-built Z1-based Superbikes?

No one can forget the Muzzy-built Z1-based Superbikes piloted by Eddie Lawson. (Cycle World Archives/)

Z1′s big air-cooled inline-four was also a revolution in drag racing. Before the Z1 brought the potential for killer horsepower in a single powerplant, drag builders were joining together two, three, or even four smaller engines.

Why reproduce cylinder heads, and why now, many years after the production of “well over 100,000 vehicles” has ceased? How many times over 40 years can you push in new valve guides or shrink in new valve seats before you need a new head? And connoisseurs of the big air-cooled sit-ups want to ride them, not just gaze at a static showpiece.

Kawasaki is reproducing Z1 heads in 2020. There are only so many times you can rebuild a head—and Z1 owners want to ride, not look at their machines. (Kawasaki/)

Just to revisit some salient points, Muzzy’s best engine gave 152 hp at 10,250 rpm, and he said, “Things start to go bad really fast when you get near 11,000.” In the early days of Superbike it was believed by some that only older, wiser riders could master such giants. Then someone at Kawasaki said, “What about this kid Freddie Spencer? Anyone know his phone number?” Freddie put an end to all that older-and-wiser talk right away.

It wasn’t easy to race those big 1,000cc air-cooleds because in truth, their engines were far ahead of their production chassis, suspensions, and tires. Winning races therefore required a lot of professional attention to nearly every part. And that in turn drove the next revolution in production motorcycles—design of bikes that could be production-raced with minimal changes: Ninjas, Secas, Hurricanes. And that in turn brought forth the Supersport revolution—the years of intensive competition in 600, 750, and 1,000 classes, enjoyed by large numbers of amateur and professional riders.

Racing those big sit-ups in 1975–‘82 was a crazy, creative scene. Each AMA district had its own tech inspector in those days, so teams never knew which carburetors a given tech chief would deem legal on a given day. So they sent watchers to report instantly which carbs were being let through. If a bike with Keihin race carbs was approved, teams waiting in the tech line would pull their bored-oversize but lower-performing stock carbs and fit their Keihins. 

Brakes were particularly hard-hit by the new horsepower, so the US team had its own iron discs cast and finished by a series of steps, alternating between machining and furnace annealing, resulting in discs that remained stable in racing and did not taco or cone. In competition, desperation is the true mother of invention.

From Today’s Press Release

“Kawasaki will reproduce the cylinder heads using current methods based on original part design plans and specifications. The cylinder heads will be manufactured by Kawasaki Heavy Industries Ltd. in Japan and will be available in two colors, silver and black.

Kawasaki’s reproduced Z1 heads are available in a black or silver finish. (Kawasaki/)

“To be one of the first to receive one of these reproduced cylinder heads, preorder can be placed by contacting your local Kawasaki dealership and placing an order before June 30, 2020. Orders placed by this date are expected to arrive by fall 2020. For more information please contact your local Kawasaki dealer or visit kawasaki.com.”

The release continues, listing the models of Z1, KZ900, and KZ1000 that are compatible with this head, plus its physical details.

Source

[Tym]

I can see it now, 2057, Kawasaki reproduces KLR parts because, we cant build new chit fuckit!...