As I explored the characteristics of the Doremi Assortment Kawasaki Z900RS heritage physique kits, I found myself hurtling down a Z1-R-shaped rabbit hole. While browsing through an extensive array of Z1-R motorcycle images online, my attention was drawn to one particular bike that noticeably deviated from its peers. I remembered noticing an identical Z1-R model sometime later when I installed a Nitron NTR R2 rear shock on my Z900RS. Initially, I had never taken the time to scrutinize it further because my initial impression was that it was simply a heavily modified restomod. After further investigation, I found that this unique practice, specifically the Kawasaki Z1-R, stands out as an exceptional example of its kind.
The collaborative endeavour that resulted in this unique Kawasaki Z1-R was a joint project between renowned British suspension experts Nitron and Japan’s esteemed workshop, Bull Dock. Dubbed the 1230R GT-M, this impressive exercise program stands out as one of the most innovative and engaging I’ve had the pleasure of encountering.
Located approximately one and a half hours north of Tokyo. Masashuiko Waiku, a former engineer, founded and runs the workshop, having debuted the model in 2001. In Japan, his workshop stands out as a premier destination for bespoke bicycle solutions, boasting an impressive scale that sets it apart from others of similar ilk, with services encompassing customisation, restoration, and fine-tuning.
Masa’s approach to bike customization centers on crafting a bespoke machine, but his attention isn’t solely fixated on meticulously honed engines. When requested, Bull Dock is capable of rebuilding a bicycle from the ground up, transforming its frame, refining its components, and optimizing performance to achieve unparalleled results. Dubbed the GT-M series, this moniker’s brevity belies its significance as an abbreviation for ‘Rear Tuning Machine’, but it is worth noting that the collective passion of these enthusiasts lies in meticulously transforming classic Z models from Kawasaki into showstopping masterpieces.
The Nitron 1230R GT-M project commenced when Nitron’s Japanese office collaborated with Bull Dock to develop a motorcycle that prominently featured their products. Recognizing Nitro’s unwavering commitment to the world of motorsports, Masahiko devised a strategic plan to design and build a motorbike capable of excelling on both the road and the track. The donor is keen on acquiring a motorcycle that stands out in terms of its significance and visual impact. The iconic Kawasaki Z1-R from 1978: a prime contender.
After securing a suitable donor, the bicycle was comprehensively disassembled to prepare for the GT-M project’s commencement.
Utilizing their proprietary jigs, Bull Dock meticulously reconfigures each frame from the ground up, leveraging the versatility of the original bicycle’s chassis. Before commencing any welding process, a temporary or dummy engine is initially installed into the vehicle’s chassis to ensure accurate positioning and alignment during fabrication.
As soon as the happy owner of this bike’s sleek new body had finished admiring its every detail, it underwent a vital transformation. The new Z1-R body features an enhanced framework comprising multiple strategically placed gussets and reinforcements designed to effectively address any structural concerns. The subframe has undergone thorough revisions, and the swingarm axle has been redesigned to accommodate a significantly wider and 15 millimeters longer boxed aluminum component. Following the completion of modifications, the body was carefully encapsulated and wrapped in a protective layer of carbon fibre film.
The subsequent arrival features an all-new suspension, braking, and wheel package. Underneath Nitron’s proprietary steering, the Z1-R features a pair of specially calibrated 43mm black chrome forks, each incorporating bespoke Nitron internal components carefully tailored to optimize performance. At the rear, a high-end pair of Nitron NTR R3 piggyback shocks reside in adjustable brackets, allowing riders to fine-tune their bike’s handling to suit specific conditions. To effectively curb energy loss, Bull Dock opted for a comprehensive Brembo braking system featuring dual radial calipers at the front. The drilled disks float as scale models, with all fluids flowing through robust braided hoses. Utilizing cutting-edge techniques to interact with elements was merely the beginning of our endeavour. Masaharu opted for a pair of 17-inch carbon fibre racing rims from Lavorante to equip his high-performance vehicle’s wheels. By pairing them with the half, carbon rims effectively reduce overall weight and unsprung mass, which are two key ways to enhance performance.
The Kawasaki Z1-R, sourced from the company’s manufacturing unit, boasted a 1015cc inline-four engine, identical to that found in the Z1000 model. The compact engine generated a respectable 94 horsepower and 63 Newton-meters of torque. While these numbers may seem modest compared to those of immediately’s sport bikes, the Z1-R was by no means a pushover. With a deft touch, I twist the throttle wide open and charge through the five-speed gear field, propelling me to a quarter-mile finish in a fraction shy of 12 seconds. Should I manage to nurse it through the pin, I’d eventually crest at 136mph (220km) on the speedometer’s readout. As their competitive spirits were reignited, Nitron and Bull Dock realized they could still push themselves to achieve greater things.
The bike’s engine is a masterfully crafted blend of high-performance enhancements and components. With an internally installed GPZX head boasting enlarged valves. The titanium valves and springs are complemented by meticulously polished consumption and exhaust ports. The inventory cameras have been upgraded with race-enhanced options, featuring JE-domed piston technology. The cylinders have been bored to optimize a capacity of 1203cc, thereby redefining the bike’s identity.
Four Mikuni TMR carburetors, featuring velocity stacks, supply gas to the engine. Onboard, there’s a multi-function PC that centrally manages the entire setup and features a reliable twin ignition system. The transmission has undergone an upgrade to a 6-speed gearset, which is now controlled by a rapid-fire shifter and high-performance clutch, designed to optimize shifting dynamics and overall ride quality. Ensuring the overall system temperature remains cool is a critical capability achieved through the trochoid oil pump’s efficient operation, which is further augmented by a larger oil cooler strategically positioned near the intake manifold. The Bull dock’s engine bundle was completed with a high-performance full-titanium 4-into-1 exhaust system designed and manufactured by renowned expert Win McCoy.
While sharing a striking similarity with the Z1-R’s manufacturing unit bodywork, every component on this unique bike is tailored specifically for its purpose. With meticulous attention to detail, Bull Dock crafted an exact replica of Kawasaki’s iconic gas tank design using lightweight aluminum, replicating the original with precision and flair. The design’s focus on reducing weight and complexity was further accentuated by the development of a single-piece, fibre-reinforced polymer (FRP) monocoque structure for the tail, seat, and faceted cowling assembly. The entrance and rear fenders have been precision-crafted from lightweight carbon fibre, while the sleek cockpit surround accommodates a high-performance Stack ST 200 Clubman Tachometer, alongside a fuel gauge and comprehensive warning light array.
Initially, the Z1-R boasted a sleek metallic silver blue finish, but the 1203R GT-M truly turns heads in its striking Nitron turquoise blue, offset by crisp white accents, pinstripes, decals, and badges.
Ultimately, the entire endeavour’s final stages arrived at this point, rendering the record far too extensive to comprehensively document without sacrificing clarity. Custom features include machined-alloy rear units, clip-on handlebars, GaleSpeed grasp cylinders, swapped engine blocks from a modern Kawasaki, a high-performance steering damper, and a custom-made primary clamp, showcasing the bike’s unique blend of functionality and style.
The comprehensive results of Bull Dock’s meticulous work on the Kawasaki Z1-R are truly remarkable. The Nitron 1203R GT-M tips the scales at just 190kg, a significant reduction from its previous weight of 238kg, while its engine delivers a robust 150hp. With the blend of impressive figures, including the benefits of premium Nitron suspension, high-performance Brembo brakes, and lustrous Candy Carbon wheels, you’ve essentially crafted a timeless Kawasaki that can easily outshine many modern sportbikes.
