

It looks like Kawasaki has hit a home run with its new Z900RS retro standard, and no-one in the press corps has even ridden it yet.

It’s a homage to the mighty inline fours of yore like the Z1 (below) and based on the well-regarded Z900—itself a cracking performer that Cycle World’s road testers placed ahead of the Triumph Street Triple and Yamaha FZ-09 in a group test a few weeks ago.

We haven’t seen such feverish interest in a bike since Husqvarna revealed the Svartpilen and Vitpilen exactly two years ago. But the Austrians have inexplicably been dragging their feet on releasing those bikes.

And even if when they’re revealed at the Italian EICMA show in a few days, there’s a real danger that Kawasaki will steal Husky’s thunder with the production-ready Z900RS.

Kawasaki has wisely taken a leaf out of the BMW and Yamaha playbooks, and has given pre-production samples of the Z900RS to leading custom builders to work their magic. It’s called the Beyond Z project.

So let’s take a closer look at the mods that Moto Corse, Doremi and Bito have made. A few aspects of the Z900RS are already rankling with potential buyers, and it looks like the builders have similar concerns.

The specialist Kawasaki tuning shop Bito R&D is located deep in the sparsely populated mountain woodlands of the Hyōgo Prefecture, an eight-hour drive west of Tokyo. In the 70s, owner Jo Bito worked with Pops Yoshimura on Z1 race bikes, but today he takes orders for his JB-Power brand parts from all over the world—including factory teams battling in MotoGP.

Bito-san is the ‘Z Master,’ a craftsman who knows the original Z1 series inside and out, and he’s built his Z900RS custom as if he was his own client. “The Z900RS handles like a modern motorcycle: it’s light and turns well,” he says. “But if it was up to me, I’d prefer handling that was a little more relaxed. So I changed to 18-inch wheels, and specifically selected thinner tires.”

The JB-Power ‘Magtan’ wheels weigh about half as much as the stock wheels. The standard Z900RS brakes perform just fine as is, but Bito has still opted for machined aluminum calipers with six pistons and cast iron discs for better brake touch and control.

The exhaust is a 4-into-1 layout—“suitable for a modern machine”— made of titanium. Again, it weighs half as much as the stock piece. But the masterpiece is less obvious: a quick-change mechanism equipped on the rear wheel axle shaft. The system was originally developed to allow quick tire changes in endurance races, but it greatly simplifies day-to-day maintenance chores.

There’s a geometry change too. “Fork offset can significantly affect handling,” notes Bito-san. “Increasing it from the 35 mm of the standard model to 40 mm results in an even more hands-on ride feel.” He’s also swapped out the engine hangers, fender stays and headlamp and turn signal brackets for high-quality machined aluminium pieces. Finally, to help bring out the ‘go where you think’ feeling, the rider triangle of the handlebars, seat and footpegs is tweaked for a more relaxed posture.

JB-Power parts Handcrafted titanium 4-into-1 exhaust pipe with megaphone silencer | Aluminum rear sprocket | Adjustable-offset fork triple-clamp set | Machined aluminum radial-mount front brake calipers (6-piston) | 320mm cast iron floating front brake discs | 250mm cast iron rear brake disc | Magtan JB4 forged magnesium wheels F: 3.00-18 R: 4.50-18 | Seat leather, cushioning | Machined aluminum footpegs, headlamp, fender and turn-signal stays, engine covers, rear wheel quick-change system, chain adjuster and racing stand hooks | AP Racing/Goodridge Front brake master, steel-braided brake lines | Brembo 2-piston rear brake caliper

Builder: Bito R&D/JB-Power

There are two sides to the town of Kurashiki, home to the Doremi Collection store. There are the white-walled facades left over from the Japan of old, and the sleek high-rises of a modern city. In the storefront window, beautifully restored Z1 and Zephyr models pull your gaze. But in the workshop out back, owner Hiroshi Take has created a scene just like a backyard garage in rural America.

Take-san also looked to the US for inspiration with his Z900RS custom. “I chose the Z1 racers that were active in AMA in the late 70s,” he says. “At that time, Yoshimura was still fielding a Z1 with Wes Cooley as the rider.” To bring back this style, part of the frame had to be redesigned. The main frame’s upper rails are closer together, and the seat rail angle is flatter.

Engine guards jut out with the aim of creating an old-school appearance of volume, along with new engine covers. The Z1’s quad-style exhaust system was iconic, so Take-san has taken apart a stock muffler, removed its internals, and fitted them into a new quad-style muffler. He’s used steel to reproduce the exhaust note that Zeds had back in the day.

Meticulous too with the bodywork, Take-san has fitted a Z2-type tail cowl and the side covers from a Zephyr, plus a steel front fender. The taillight, turn signals and mirrors are also Z2 parts, but the lighting internals are now LEDs. The headlamp uses a modified Z1 case, giving it a classical style, but this too houses a LED unit.

AMA-style disc brakes combined with 18-inch Morris mag wheels perfectly match the bikes of the era, and to achieve the right silhouette, the swingarm was shortened two centimeters. “We are entering the age of cosplay,” says Take-san. “Simply adding rearsets and an aftermarket exhaust will not be enough to stand out.”

Modifications

Doremi Collection parts Z2-type quad-style exhaust system | Titanium water pipe | ‘Dummy’ frame | Machined aluminum upper triple-clamp | 18″ Morris mag wheels | Superbike handlebar and machined aluminum bar ends | Custom seat | Machined aluminum radiator guard, points cover and engine hangers | Grab bar | Z2-type chrome front fender, stays, mirrors, turn signals, side covers, tail cowl, rear fender, taillight | Modified Z1 headlamp and chain case | K-Factory Machined aluminum brake lever, clutch lever, lever guards, footpegs, front sprocket cover | Front axle sliders and engine sliders | Sunstar KR-type front brake discs and rear brake disc | Hyper Pro Rear suspension equipped with seat height adjuster

Builder: Doremi Collection

Moto Corse is well known in Japan as an importer of high-end models like Bimota and Vyrus, and as a builder of Ducati, Bimota, and MV Agusta customs. But owner Shin Kondo’s first bike was a Kawasaki. “I had an export model H2, blue with rainbow striping. The rush of acceleration was intoxicating.”

Kondo-san studied dozens of CG illustrations combining various styling, graphics and exhaust options. For the tank, he chose Moto Corse’s original carbon black, divided into both matte and glossy finishes. The bodywork is now carbon fiber throughout, and the stock aluminum engine hangers and front fender supports have also been swapped out for carbon pieces.

Making just a slight change to the seat cushion shape has given the top line of the bike a different look, and shortening the tail end by roughly three centimeters gives a more unified feel. The work is a step-by-step search for the golden ratio that makes a machine look its best.

“Customers will buy this bike because they like the design,” says Kondo-san. “To drastically alter it would be presumptuous. Our job is like polishing a gemstone.” His exacting standards are evident throughout, but especially in the titanium exhaust system. From the center pipe to the end of the silencer, the pipe diameter increases in a reverse taper

The front and rear suspension is now Öhlins. An inverted fork that fits the Z900RS does not exist in Öhlins’ current line-up, so the fork on Kondo-san’s custom machine is a special version created based on an Italian-brand OEM part adjusted for length, with original bottom clamps. Brembo calipers are matched to Alth ventilated discs—which are actually two machined stainless steel discs spot-welded together, for a ‘mellow’ brake feel.

The wheels are custom, made from carbon and featuring a seven-spoke design that suits the vibe of the Z900RS. (To complement the classically wide tank design, a 200mm rear tire was selected.)

“We’ll need to ride it thoroughly now, to highlight any areas for improvement. But in the near future, I would like to look at tuning the engine too,” says Kondo-san.

It will be interesting to see how Moto Corse’s Z progresses from here…

Modifications

Moto Corse parts 4-2-1 titanium full exhaust: titanium flanges, lobster-tail design header pipes and tapered silencer with teardrop honeycomb end cap | CNC aluminum rear sprocket | Titanium gold frame powder coat | CNC machined aluminum upper triple clamp | Special specification Öhlins R&T 43mm front fork, Öhlins S46 fully adjustable rear shock with Moto Corse CNC machined aluminum linkage | Calf-leather seat (perforated, stitching, diamond-quilting) | CNC machined aluminum accessories: smartphone holder, fuel tank cap, DBT preload adjuster dial | Axle sliders | Dry carbon parts: meter housing, headlamp housing, steering neck cover, pivot plate cover, radiator shrouds, throttle body cover, engine supports (x4), preload adjuster support, heel guards, rear fender, license plate support, license plate base | Titanium radiator guard, handlebar ends, frame caps, luggage hooks, tire valve caps, banjo bolts, front fender supports, front brake master cylinder, clutch lever, radiator cover | Brembo CNC machined racing radial-pump front brake master cylinder | GP4RX CNC machined radial-mount front brake calipers | Supersport P34/2 CNC machined rear caliper + CNC machined aluminum caliper support | Alth stainless steel ventilated floating disc brakes | BST7 straight-spoke carbon wheels F: MT3.50-17 R: MT6.00-17 | Magical Racing Dry carbon handlebars

Builder: Moto Corse