If you lined up the current crop of sportbikes without their paint or sticker packs, most people would struggle to tell the difference of the very similar silhouettes. As the bikes become more track focussed, so does their aerodynamic bodywork and the days of designers doing something truly fun and funky in the category are gone. But there is still a way to have a bike look truly beautiful and have the performance to match and the method is known as the resto-mod. In the bike world, there is simply nobody that does them like Japan’s AC Sanctuary, and their latest build RCM-558 is a KZ1000Mk-II that’s as good as it gets.

The resto-mod scene is booming across the automotive world with shows like SEMA dominated by the beautiful bodies of the ’60s and ’70s that are packing truly 21st century performance. From Singer with their incredible 911’s to the RingBrothers amazing American muscle, they are the thing to have. But unless you’ve got the best part of a million dollars then you may want to look towards two-wheels and it is here that AC Sanctuary has been leading the pack since 1995.

Headed by the very hands-on Hiroyuki Nakamura, the RCM series of bikes (Real Complete Machine), delivers to the client a 1970s muscle bike that is totally transformed until it is, in reality, a ‘new’motorcycle. In fact their RCM series comes with a warranty, free first service, and delivery to your door with all the work done for road registration. Nakamura-san has had a lifelong love affair with Kawasaki’s Z bikes, but with them proving harder and harder to find, he has the US division of the company hunting for examples in the dry desert air of Arizona and Nevada.

For build 558 the client from Kanagawa Prefecture specified a KZ MkII and with the donor bike in the shop, it was stripped back to a bare frame that was then bead blasted back to raw steel. From here it has been given their Stage-II reinforcement package, which gives the frame increased rigidity for improved handling. With it painted black and new bearings thrown in, a stunning alloy Sculpture swingarm by AC is slotted in. With its extra bracing, lightweight design and tailored to ensure perfect chain alignment, it is simply a work of art.

Keeping to the original look of the KZ, a twin shock setup is retained, but little is compromised with high-end Ohlins shocks taking care of business. At the front, Nakamura-san made what he calls a “very rare exception”, allowing the owner to supply his own set of Ohlins forks that slot into a custom set of billet alloy triple trees. The braking is just as impressive with AC machined brackets allowing for the front end to wear a set of twin Brembo calipers and massive floating drilled discs. The rear is just as good, with a race-style under slung Brembo caliper grabbing a new disc.

With all modern sportbikes settling on 17in rims, the wheel and tyre options are endless, so Nakamura-san sets up his bikes to use the same. In the form of lightweight Oz Racing rims and quality Pirelli rubber, maximum grip and reduced unsprung mass are perfectly taken care of. Above the front tyre is the first of the bodywork, a front fender by Nitro Racing, while at the rear there is a full carbon fibre hugger bolted to the swingarm. The stock fuel tank, side covers and tail are retained but the paint job is simply out of this world. With the photos barely doing justice to the deep gloss and perfect pinstripes.

Like the front fender, that almost stock but not looking seat comes from Nitro Racing and hits the retro mark spot on. One of the joys of an AC bike is their comfort and matching the seat is the easy to place your hand’s on bars, that sit atop a set of custom risers. The lighting is all retro with the controls a mix of old and new; overhauled gauges, joining modern tech in the form of Brembo radial master cylinders, new switchgear, and a Yoshi gauge that monitors the engine’s vital signs.

That engine is of course the Kawasaki 1050cc four-cylinder that has been thoroughly rebuilt from top to bottom for improved reliability and extra power. The big oil cooler and braided lines ensure it’ll never overheat, while the full respray in black with RCM covers and stainless bolts has the donk looking good enough to eat off. A new bank of carbs is fed by four individual velocity stacks that deliver a hell of an intake roar. But it’s that Nitro Racing full exhaust system made from Titanium that steals the show.

As you read this the new owner will be taking delivery of his stunning AC Sanctuary resto-mod that he’s been dreaming about for years. As for Nakamura-san, he’s already working on bike 560 and so long as he can find donors, he’ll continue to craft the best bikes it’s possible to produce. 

[ AC Sanctuary ]