A Cross-Continental Collaboration: SUZUKI GSX1000S KATANA Custom by SANCTUARY
SANCTUARY's GSX1000S KATANA
One of the concepts of Sanctuary's complete custom RCMs is equipping the bike with the latest 17-inch high-grip tires for optimum enjoyment. This GSX1000S marks a milestone for such RCMs, being the 500th machine built and bearing the serial number RCM-500. The modern-style single seat and paint job are a bit different from the RCM customs we have seen in the past.
"This custom was ordered by a customer from the United States. He is a fan of our RCMs. He often comes to Japan on business, and from the time our shop was located in Tokyo (Summer 2000 - Spring 2015), he visited every time he came to Japan. He now owns many motorcycles and supercars, but it was in 2018 that he wanted to add an RCM to his collection. The base bike is a Katana that he worked a part-time job in order to save up for when he was young; it is a 1000S, not an 1100. He kept the bike all this time, and had it sitting in a corner of his garage,” says Nakamura of Sanctuary, recounting the beginnings of this custom.
The bike was then taken to RCM USA, a North American group company of AC Sanctuary, and disassembled there. The necessary parts were sent to Sanctuary's main office in Japan, and work began in the fall of 2019. As with the Kawasaki Z series, which the shop handles extensively, they also have experience building RCM Katanas, and the methods are well established, so the procedure should have been the same, but Nakamura says it was a little different.
"The owner of this bike was very passionate about his ideal machine, which is of course also true for owners in Japan, but it was quite a challenge to make it fit his vision. In Japan, the shape of the original bike is often kept as is; even when a single seat cowl is made for a Z1-R, the shape of the Z1-R is kept as much as possible. For this custom, however, the single seat has a modern shape, and we had to check the balance of the entire bike to see if the shape would fit, and at the same time, we had to add functionality to it. We also had to rebuild the seat rail, and we made the seat striker so that the seat could be opened and closed with a key, and so that the battery could be accessed when the seat was opened, as well as used as a storage space. My biggest impression was that we did a lot of one-off work like that, the kind of custom work that used to be done in the past,” said Nakamura.
The main frame was modified by lowering the swingarm pivot to maintain the rear ride height without making it difficult to ride as if it had just been raised. After checking the engine, the crankshaft, which was almost unusable, was replaced with one that was modified from a GSX1100S. The owner checked up on the progress every time he came to Japan, and while mostly satisfied that the bike matched his vision, he also placed additional orders. The left and right dual exhaust and steering damper were added after finishing touches were already starting to be made.
"We drew out designs and made full use of various methods to give form to his ideas. As I mentioned earlier, we also had to make sure they were functional and durable. It had been a while since I experienced the difficulty building from scratch like that,” said Nakamura.
The RCM-500, which took three years to complete, is more than unique, not only in its hardware specifications, but also in its exterior appearance that features a carbon and metal looking paint job. It was later tested on a closed course and displayed at the EK Chain booths at both the Osaka and Tokyo Motorcycle Shows in March 2022. The desire for and dedication to the things we love is the same in both the East and the West. And after 40 years, the modern finish of this Katana RCM has surely satisfied that desire.
Handle
The smoke windshield is by OHNO SPEED, the headlight utilizes 5 LEDs, the turn signals are also LED, and the carbon monocoque body mirrors are Magical Racing NK-1. The clutch holder is a KOHKEN, the front master cylinder is a Brembo RCM, and both levers are ZETA RCM Concept.
The single-unit meter that is characteristic of the Katana was replaced with the STACK Dash System (with an LCD panel displaying engine tachometer, speed, etc.), and the meter panel is a one-off made of carbon and aluminum. The cockpit also includes an oil temperature gauge and Motogadget warning lights. The clip-on handlebars are by DAYTONA, and the stem is a SCULPTURE φ43 Stem Kit TYPE-3 with an offset of 37mm instead of 50. An Ohlins steering damper was also added.
Bodyworks
The fuel tank is made of aluminum with a hairline finish done by Sanctuary, and both the stock side covers are painted in metal and carbon by YF Design.
The modern seat cowl uses Clever Wolf's YZF-R1 cowl as a base. It was modified to match the fuel tank and to use the inside for accessory storage. The seat rail, which serves as the base of the seat cowl, was cut from the shock mounts, and then made from aluminum with high precision. A seat opener was also made.
Engine
This bike was originally a GSX1000S equipped with a 998cc engine with a smaller bore. A new GSX1100S crankshaft was prepared, and installed after correcting the bend. The pistons were changed to Wossner φ74mm forged and WPC treated rings were combined to make an 1135cc engine. The camshaft is a Yoshimura ST-1, and the ignition is an Uotani SPII.
The carburetor is a TMR-MJN φ40mm dual stack funnel specification. Red funnels were selected for the short side and black for the long side.
Chassis
The front forks are Ohlins RWU (φ43mm), and the front brakes have been significantly updated with Brembo GP4 RX calipers and RCM Concept φ320mm discs. The brake lines are from the ALLEGRI SHORTO Series, which offers lines and lengths optimized for each bike model.
The rear brakes consist of a Brembo CNC caliper and SUNSTAR disc. The exhaust system is a Nitro Racing Titanium, but it has been modified to a one-off left and right dual version.
The swingarm is a SCULPTURE Wide Swingarm with lower sway bar and racing stand hook added. The front and rear wheels are forged aluminum O-Z Racing GASS RS-A in 3.50-17/5.50-17 sizes, which can be considered the modern standard.
The frame has been reinforced with original reinforcement, and the drive chain has been modified to accommodate an offset track and a wide laydown. The pivot has been lowered by 7mm.
Gallery
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
Specifications
Part | Details |
---|---|
Engine |
Wossner High-performance Forged Piston Kit YOSHIMURA Camshaft [ST-L1] |
Carb / Intake | YOSHIMURA TMR-MJN34 Carburetor |
Exhaust | NITRO RACING 4in1 Weld Craft Titanium 3D EX Exhaust (*Special order twin tail specification) NITRO RACING Grenade Titanium Silencer Version 3 |
Frame | SCULPTURE GSX1100S φ43 Fork Stem Kit Type-3 for Clip-on Handlebars SCULPTURE Wide Swingarm, Silver, for 17-inch Wheel |
Brake | brembo RCS Brake Master Cylinder brembo GP4-RX Radial CNC 4P Caliper SUNSTAR Premium Racing Disc RCM Concept Model φ320 Hole & Slit ALLEGRI SHORTO Series Brake Hose brembo GP2-SS CNC 2P Rear Caliper SUNSTAR φ250 Hole & Slit Rear Disc |
Wheels | OZ Racing GASS RS-A 3.50-17 Front OZ Racing GASS RS-A 5.50-17 Rear |
Suspension | OHLINS RWU Front Forks OHLINS Grand Twin Rear Shocks |
Steps | NITRO RACING GSX1100S (~'99) Rearsets Kit |
Drive System | NITRO RACING GSX1100S KATANA Aluminum Machined Sprocket Cover EK CHAIN EK530RCM (BK;GP) Drive Chain |
Handle / Steering |
DAYTONA Clamp for Machined Clip-on Handlebars DAYTONA Straight Bar for Machined Clip-on Handlebars KOHKEN (KOHKEN DENKA) Mechanical Clutch Holder AVANZA SANCTUARY [ZETA x RCM] RCM Concept Flight Lever STACK ST3000 Series Stepping Oil Temperature Gauge STACK ST700SR Stack Timer Dash System Base Kit MOTOGADGET Motosign Mini Magical Racing NK1 Mirror TYPE-4 |
Oil Cooler | NITRO RACING OIL COOLER KIT 9-inch 13-row Flat Type |
Bodyworks |
OHNO-SPEED Takumi Windshield CLEVERWOLF Seat Cowl NITRO RACING Z-1/Z-2 Carbon Under Cowl Kit NITRO RACING Hanging Front Fender Beater Aluminum Tank |
Electrical | AS Uotani SPII Full Power Kit |
About SANCTUARY
SANCTUARY is a custom builder that is good at Vintage motorcycles like Z1,Ninja and KATANA. They sell special parts which were born from trial and error that mechanics had repeated mounting and testing
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.