Customising does not get cooler than this

After a while, a lot of custom designs tend to blend into a homogenous soup: variations on a standard recipe, slightly tweaked by the individual chefs.


A handful of top builders specialise in less mainstream flavours, though. One of them is Calum Pryce-Tidd of the south London workshop deBolex Engineering, who often starts with unconventional ingredients, such as an Energica Eva or a Yamaha MT-10.

The latest build from Calum and his offsider Des Francis is based on the mighty Kawasaki ZRX1200R, an intoxicating bruiser that was sold for a few years after the turn of the century.

Although it was something of a throwback, the big green machine was no slouch: it could run the quarter mile in less than 11 seconds, and pass the timing light at 200km/h.

That is comfortably faster than Kawasaki’s current Z900RS retro replica, thanks to around 90kW horsepower hitting the back wheel, courtesy of a water-cooled inline four fed by quadruple 36mm Keihin CV carbs.

That would be enough for most folks even today, but Calum has not just given the ZRX a distinctive new look.

“It was a commission from a friend, the London collector Alex Shepherd,” he revealed. “We met while on the Malle Rally a few years back, and that led to this project.”

Alex bought his ZRX1200R new and later sold it. But he regretted the sale, and bought it back a few years later, luckily with very low mileage, and still in great condition. He met up with Calum, and proposed using the ZRX as a base.

Calum is also fan of the ZRX, and the retro muscle bike vibe in general. “I’ve always loved the big AMA Superbikes,” he said, “so this felt like a good chance to ‘flex’ that design. We wanted the Kawasaki to have the ‘classic superbike’ feel, but with our unique design touches.”

As with all deBolex builds, that meant a lot of metal shaping. “The ZRX was probably one of our more challenging projects,” said Calum. “Features such as the quick-release headlight cover, and the tank and tail designs, took some head scratching to achieve.”

The mechanical upgrades are also substantial, notably in the suspension department. Up front are Maxton superbike forks with separate rebound and compression damping pistons, built to order and fitted with GP20 cartridge internals.

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The forks are hooked up with custom CNC’d yokes, and braking now comes from an ISR system with six-pot calipers and twin 310mm disks. The 17-inch wheels are the lightest aluminum models that Dymag make: the same UP7X spec used on some WSBK racers and finished in gold. The front rim is attached via a quick release spindle.

The rear end is suspended with a pair of alloy bodied, piggyback gas Maxton WR26 shocks. These are adjustable for rebound damping, compression damping, preload and ride height.

With a little CNC magic, Calum and Des converted the rear brakes to an ISR two-pot caliper system, and completed the roadholding upgrade by installing Metzeler Racetec RR suspersport tires. This ZRX1200R is going to be generating a lot more g-force than the factory bike.

The low-mileage engine is still strong, so deBolex have left the internals alone and just given the cases a Cerakote polymer-ceramic coating (along with the swing-arm and various brackets). They have upgraded the fueling, too, switching from Keihin to a stunning Yoshimura Mikuni TMR-MJN38 setup.

Gases now exit into a custom stainless exhaust system, terminated with a pair of high-riding Arrow mufflers.

The new bodywork is a medley of intriguing, unusual shapes that bear closer inspection. As you would expect on a classic Kawasaki, the color is green – but this is a more militaristic olive green, with white and gold highlights. And the frame is painted to match.

“All work is carried out in-house,” Calum explained, “from design sketches to CAD to the metal shaping stage, and then onto paint and trimming. Keeping these processes in-house enables us to achieve exactly what we set out to achieve and keeps us pushing to perfect our designs and finish quality.”

There are quick-release systems for the seat and tail that help that part of the build to run smoothly and allow for a neat install of electrics and ancillary components. The tail houses a small Shorai lithium battery and a Motogadget m.unit blue control box.

The electrics are hooked up to a Scitsu rev counter and Daytona ‘Nano’ speedo ahead of the drag-style Rizoma bars. They are finished with Renthal grips, a Domino quick-action throttle and tiny Motogadget blinkers.

Calum’s famed for his attention to detail, and you can see it everywhere on the ZRX. It is in the little things like the Samco classic black silicon hoses, and even the fasteners have all been replaced with new Pro-Bolt items.

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The ZRX1200R is a one-off of the highest order, and carries the ‘1/1’ designation given to unique, unrepeatable deBolex creations over the past eight years. But there is going to be a delay before we see another 1/1.

“This will be our last 1/1 for now, while we focus on creating a ‘Series’ run of motorcycles,” said Calum. “We are aiming to bridge the gap between production bikes and one-off customs, with a much quicker time frame and a better cost while keeping quality and design our #1 priority.”