Source: Bike Bound
Kawasaki Z1-R from AC Sanctuary…
As everyone knows, the arrival of the Honda CB750 in 1969 kicked off the superbike era. Over the next decade, a two-wheeled arms race between the big four Japanese manufacturers would produce a whole new breed of multi-cylinder superbikes that boasted engines of nearly 100 horsepower per liter, along with alloy wheels, triple disc brakes, and top speeds in excess of 130 mph.
Though the Kawasaki Z1 didn’t arrive until 1972, it made nearly as big an impact on the industry as the CB750. That’s because the 903cc DOHC “King of the Road” produced 15 more ponies than the SOHC Honda, allowing it to easily outpace the “Original Superbike” both on the drag strip and in top speed. There’s little replacement for displacement, as the saying goes.
Fast forward another five years, however, and the Z-bike was growing long in the tooth. Although the engine had been punched out to 1016cc for the KZ1000, it still made the same 82 horsepower. Meanwhile, Honda had released the six-cylinder CBX1000 — a bit of pig in the corners, but the sound of those six pistons at full chat could stir the heart of the dead — and Yamaha and Suzuki now had their own air-cooled literbikes, the XS1100 and GS1000.
It was onto this battleground that the Kawasaki Z1-R emerged, wholly distinct from anything the competition offered.
“The R has what most bikes of its type do not — a styling theme, a common design theme which runs from one end of the bike to the other. The R’s theme is straight sides and sharp corners, and the execution is with graceful, angular lines that flow so naturally from one area to the next that the bodywork sometimes appears to be all one piece.” –Cycle Guide
The design of the Z1-R remains striking to this day — one of those radical departures from the status quo that’s stood the test of time. It was the first mass-market Japanese bike to feature a handlebar-mounted front fairing, and the coffin-tank and ice-blue paint presaged the squared-off style and wilder color palette of the 80s. Larger carbs and a different exhaust pushed output up to 90 hp, while a smaller 18-inch front wheel was supposed to sharpen handling.
Unfortunately, the Z1-R didn’t quite live up to its looks in terms of ride and performance.
“You had a bike that was less than elegant on the move. ‘It doesn’t roll over bumps,’ wrote Cycle Guide, ‘it bounces from crest to crest.’ When it came to handling, the esteemed editors opined, the Z1-R’s ‘numerous rubbery frame tubes’ and flawed suspension setup allowed the Kawasaki to ‘ride harshly on the flat and … wobble in fast turns.’” –Motorcycle Classics
Fortunately, one of the world’s great Superbike whisperers, Japanese master Hiroyuki Nakamura of AC Sanctuary, knows how to exact modern performance from these air-cooled Z-bikes…while accentuating their old-school style.
The bike you see here is RCM 608 — yes, the 608th build to come out of AC Sanctuary’s Radical Custom Manufacture series. And what a handsome brute it is. Says Nakamura-san:
“This RCM-608, which is based on the Z1-R, was ordered from a faraway tropical land. The owner’s idea was not to ‘let an old bike be an old bike’ but to ‘make modifications because it is an old bike.’”
He says this Z1-R was produced “in pursuit of the qualities of a sports bike.” To that end, the frame received RCM’s stage II reinforcement, a wider swingarm, and 17-inch Italian OZ Racing GASS RS-A forged wheels.
The bike rides on Öhlins suspension and stops via Brembo brakes — a far cry from the OEM items of the late 70s. The engine was fully reconditioned and outfitted with Mikuni TMR-MJN carbs, Yoshimura cams, and a Nitro Racing titanium exhaust.
“Even if it is not a large displacement power package, it provides a satisfying feeling around town, on winding roads, and when driving at high speeds. Engine characteristics and the relationship between the engine, chassis, and handling — this is the element that determines the character of the bike and affects the total balance. In this regard, it can be said that it is an excellent machine.”
Nakamura says the Z1-R’s small bikini cowl is a privilege not available to naked bikes, allowing the workshop to create a bespoke three-gauge instrumental panel that combines fuel, oil temp, and a combined tachometer / speedometer.
The result is the most lusty-worthy Z1-R we’ve ever seen — a bike that preserves and accentuates the Z1-R’s original style while bringing the performance and handling well into the 21st century.
“The RCM-608 maintains the Z1-R’s unique characteristics while adding a subtle originality. This is a custom-made machine that the owner has longed for.”
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