From Engine to Exterior: KAWASAKI Z1(900 SUPER4) Custom by BULL DOCK
BULL DOCK's Z1(900 SUPER4)
"The engine has a displacement of 1200cc, an oil bypass line in the cylinder head, and our original 5-speed cross transmission. These are currently common specs for our GT-Ms," says BULL DOCK's Mr. Wakui of this Z1. GT-M (Genuine Tuning Machine) is the name for complete customs built by BULL DOCK. In the case of the air-cooled Z, the crankshaft is used as the starting point, and the engine, frame, and even position of various parts of the chassis are all constructed from there. The internal combustion engine is also modified in-house (more than 90% of the entire bike is done in-house), the customization process is thoroughly managed, and the bike is built with precise workmanship.
Mr. Wakui went on to explain that the 1200cc specification is standard for GT-Ms because the torque is easily handled and it has more than enough durability, so it's a level that many riders can ride without issues. The selection of carburetor, exhaust system, and exterior finish is based on the owner's riding style, usage, preferences, etc., which are discussed beforehand, and the shop is able to accommodate a wide range of needs. The carburetor can be FCR or TMR, and the diameter and funnels can be selected too. The head cover can be finished in black wrinkle paint, as with this bike, or it can be done in another color, like red. The engine covers can be chosen in the same way, as well as the exterior coloring. For this bike, a light metallic orange base and a tiger pattern finish were chosen. This color is used relatively often for GT-Ms, but in the case of this Z, the engine, including the aforementioned cylinder head cover, is finished in a subdued black tone, which works well as a contrast. These types of details, that you can't help being captivated by, are also business as usual for BULL DOCK's G-TMs. The rest of the content that is built on top of that is also amazing, yet feels so natural. And we'd like to make note that this is true of all the customs this shop does.
Handle
The cockpit has a Z-like configuration with a modern feel. The handlebars that mount under the top bridge are clip-ons, and Brembo RCS brake/clutch master cylinders as well as Moto Master reservoirs were selected. A YOSHIMURA Progress Meter is also installed. The stem with cutouts is a Mccoy adjustable offset type.
Bodyworks
The seat is a Mccoy Supreme Seat, which improves handling and seating comfort while reducing fatigue. The exterior coloring is done in a tiger pattern.
Engine
The engine is 1200cc with forged pistons by Pistal Racing, and an oil bypass line has been added to the cylinder head. The transmission is a BULL DOCK original 5-speed cross transmission, and the engine covers, outboard and offset sprockets, and step kit are all by Mccoy.
The carburetor is a YOSHIMURA FCR-MJN with black wrinkle paint finish on the top cap. The frame was also rebuilt to the necessary dimensions.
Intake & Exhaust
The exhaust system is a full titanium Win Mccoy NEO Full Exhaust with a short, black Win Mccoy NEO Silencer.
Chassis
The front forks are Ohlins RWU, and the front brakes are a combination of Brembo radial billet calipers and SUNSTAR x Mccoy φ320 discs.
The Mccoy swingarm is made of 7N01 extruded aluminum with a pentagonal two-beam reinforced cross-section and is finished with an RX coating. The front and rear wheels are Marchesini Forged Aluminum M7RS in 3.50-17/6.00-17 sizes, with Bridgestone RS10 120/70 and 190/50 sized tires. The drive chain is by RK and has been converted to 520 size.
The rear brake caliper is a Brembo CNC (2P) and the disc is by SUNSTAR. The rear shocks are Ohlins Blackline.
Gallery
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
Specifications
Part | Details |
---|---|
Engine | PISTAL RACING φ76mm Forged Pistons BULL DOCK Mccoy 5-speed Cross Transmission BULL DOCK Mccoy Offset Sprocket & Outboard Kit BULL DOCK Mccoy Billet Clutch Cover BULL DOCK Mccoy Kick Shaft Cover |
Carb / Intake | YOSHIMURA FCR-MJN39 Carburetor |
Exhaust |
BULL DOCK Win Mccoy NEO Full Exhaust System BULL DOCK Win Mccoy NEO Silencer, Short / Black |
Frame | BULL DOCK Mccoy RX Coated Swingarm |
Brake | brembo RCS Brake Master Cylinder brembo GP4 RX Front Caliper Mccoy x SUNSTAR Collaboration φ320mm Front Disc brembo GP2-SS Rear Caliper SUNSTAR Works Expand Rear Disc |
Wheels | Marchesini M7RS Genesi 3.50-17 Front Wheel Marchesini M7RS Genesi 6.00-17 Rear Wheel |
Suspension | OHLINS Front Fork RWU OHLINS Legend Twin Rear Suspension |
Steps | BULL DOCK Mccoy Rearsets |
Drive System | RK 520XXW Drive Chain |
Handle / Steering | BULL DOCK Mccoy Clip-on Handlebars brembo RCS Clutch Master Cylinder YOSHIMURA PRO-GRESS2 Multi-temp Meter BULL DOCK Mccoy Stem Set for Upright Φ43mm Fork (Lightweight Racing Type Top Bridge Specification) |
Seat | BULL DOCK Mccoy x Supreme Seat Z1/2 |
Bodyworks | BULL DOCK Mccoy Dry Carbon Front Fender BULL DOCK Mccoy Fender Eliminator Kit BULL DOCK Mccoy Carbon Rear Inner Fender |
Electrical | BULL DOCK Mccoy Dynamo / One-Way Clutch Kit |
About BULL DOCK
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.
Original Source of this Article
Heritage & Legends


editor
Hakuyo
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.