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Continuous Cutting-Edge Demonstration: Z1-R Custom

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 12 min read



BULL DOCK has been producing GT-M (Genuine Tuning Machine) full customizations of air-cooled Zs with specifications that match or exceed those of modern models. The production began about 20 years ago, and has evolved to incorporate the latest techniques and methods of each era. This Z1-R is one of the most up-to-date versions of their GT-M. With a displacement of 1260cc, maximum output of 154ps at 9600rpm, 6-speed transmission, and a dry weight of 184kg (the stock Z1-R weighs 264kg, so its about 80kg lighter), it meets modern specifications. The engine displacement is also large for a Z Custom, but unlike the larger models of the past, the Z1-R has plenty of torque and easy-to-manage output characteristics, and was built with durability in mind. Moreover, over the past 20 years, the design of the Z Custom itself has continued to evolve. While working on these Z customizations the staff have continuously been able to improve the level of their skills by discovering details about the Z itself, and scrutinizing the best points for machining and positioning parts. This know-how was not acquired overnight.


It is said that the founder of Porsche also mentioned that "the latest is always the best." The same applies to motorcycles, where new models are constantly being introduced and considered superior. By incorporating the latest elements into the Z, it can be further improved. However, not every new thing is necessarily suitable for the Z. That's why it's important to discern and incorporate them wisely. To do so, a deeper understanding of the Z is necessary. The Z1-R that embodies these elements always showcases the latest technology. Furthermore, there are ongoing developments in future parts production and testing. This piques great interest as it will be reflected in new complete customizations and the specifications of the next Z1-R.



The bikini cowl is McCoy. The overall color is pearl white with a slightly darker shade of aqua, and it features double pin-stripes that closely resemble the original pattern. The left and right master cylinders are GALE SPEED Elaborate, and the handlebar-mounted mirrors are Magical Racing NK-1 Mirror Type 1. The headlights have been converted to LED.


The fuel tank is mounted with a McCoy aluminum tank, which not only reduces weight but also alleviates concerns about rust formation and residue commonly found in older bikes.


The integrated seat cowl, spanning from the side cover to the tail cowl, is the McCoy Z1R seat cowl, complemented by the McCoy Supreme seat that enhances comfort and maneuverability while conforming to its shape. The fender eliminator kit is also from McCoy, and the rear blinkers are neatly mounted on the side of the license plate holder.



The McCoy steering stem, which is a variable offset type optimized for both front and rear 17-inch wheels, was originally black in color, but it is currently equipped with a silver one. In front of that, a Hyperpro steering damper is installed in a horizontal position. The clip-on handlebars are McCoy-made, and the meter panel is a one-off made of carbon. The meter features a combination of an electric analog tachometer and a multifunction digital display, specifically the STACK ST700SR+ST3315 fuel gauge, and it is additionally equipped with a Yoshimura progress meter.



In the photo, the head bypass and twin plugs are easily visible. The carburetor uses Yoshimura's TMR-MJN Φ40mm dual stack funnel specification.

Intake & Exhaust


The BULL DOCK frame was carefully modified and reinforced to achieve optimal values for the Z1-R. The engine underwent a bore-up process using Pistal Racing × McCoy forged pistons, resulting in a displacement of 1260cc. After replacing the head with the J-series model, head bypass and dual plug conversion were added, along with the ST-1 camshaft. A McCoy 6-speed cross transmission and gear-type oil pump were utilized. The electrical system was upgraded, and the front blinkers were positioned next to the oil cooler.



The front brake utilizes the Brembo GP4 RX caliper and Sunstar Omega brake disc. The rear brake combines the Brembo GP2-SS CNC P2 caliper with the Sunstar Works Expand brake disc. The exhaust features a gold-colored shell and a short silencer, equipped with the Win McCoy Neo full titanium 4-1 (internal 4-2-1) system. The rear shock and Φ43mm front forks are equipped with the McCoy Nitron, designed to match the GT-M specifications.


The swingarm is made of 7N01 aluminum with a triple cross-section shape resembling the letter "N," manufactured by McCoy. For testing purposes, it is equipped with serrations and slots that allow for adjustable shock positions. The wheels are the Bulldog original Lavorante Sfidare, made of ultra-lightweight and high-strength forged aluminum. They are fitted with 3.50-17/6.00-17 size tires and also come with a carbon rear inner fender. The drive chain is RK520XXW, and the rear sprocket is fitted with Sunstar x McCoy.


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Part Details
Engine Mccoy x PISTAL RACING Φ78mm Forged Piston
Mccoy 6-speed Cross Transmission
Mccoy Oil Pump Geared Casting Model
Carb / Intake YOSHIMURA TMR-MJN 40mm dia. Carburetor
YOSHIMURA Dual Stack Funnel System Basic KIT for TMR40
YOSHIMURA Original Aluminum Funnel for YOSHIMURA TMR-MJN/TMR40
Exhaust Win Mccoy NEO Full Exhaust Gradient
Brake GALE SPEED Elaborate Master Cylinder [VRE Series] Brake Master
Mccoy Rear Brake Master
SUNSTAR Works Expand Disc
SUNSTAR Omega Disk
Suspension Mccoy x NITRON Φ43mm Front Fork
Mccoy x NITRON Twin Shock
Steps Mccoy Backstep TYPEII
Drive System Mccoy Outboard & Offset Sprocket
Mccoy x SUNSTAR Rear Sprocket
RK 520XXW Drive Chain
Handle / Steering BULL DOCK Stem Kit
HYPERPRO Steering Damper
Mccoy Separate Handle
STACK ST700SR Stuck Timer Dash System Base Kit
STACK ST3000 Series Stepping Fuel Gauge
YOSHIMURA Digital Multi Temp Meter ASSY Model-K
GALE SPEED Elaborate Clutch Master Cylinder
Magical Racing NK1 Mirror TYPE-1
Seat Mccoy Supreme Sheet
Bodyworks BULL DOCK Front Cowl
Mccoy Aluminum Tank Z1R
BULL DOCK Single Seat
BULL DOCK Mccoy Fender Eliminator Kit
Mccoy Dry Carbon Front Fender
Mccoy Carbon Rear Inner Fender


A motorcycle customization and tuning store focused on the Kawasaki Z series. The "Mccoy Series" is the original parts developed by BULL DOCK in pursuit of further performance for the complete machines. Each and every one of these parts is manufactured with a strong sense of commitment.

BULL DOCK brand page

Original Source of this Article

Heritage & Legends




A foreigner who rides in Japan, Japanese call this "Gaijin Rider". Third year in the Webike global team. He feels and shares the real bike life in Japan then presents you how interesting Japanese customs are.