A Machine Built to Ride and Be Remembered: SUZUKI GSX1000S KATANA Custom by Mellows

Mellows' GSX1000S KATANA

In the late 1970s to early ’80s, the two-valve YOSHIMURA GS, painted red with white lines, dominated AMA Superbike racing. This custom machine channels that spirit but in a striking monochrome scheme. And while it may look like a GS, the base is actually something more rare: the GS’s successor, the four-valve GSX1000S KATANA, a model Suzuki built in just 3,000 units for race homologation. Once you hear that this build was done by Mr. Nakagawa of Mellows, it all starts to make sense.

“The owner came up with the idea: take a KATANA 1000 and give it a naked look with bar handlebars. The concept was ‘an AMA Superbike you can ride around town',” Nakagawa says. With that vision in place, everything else followed naturally. What brought this machine to life was the perfect overlap of two dedicated minds—the owner's passion, parts-hunting ability, and detailed concept, and Nakagawa’s craftsmanship and precision in bringing it all together.

The engine was built by SOHC Engineering and big bored to 1015cc with one-off street pistons. The frame was measured and corrected while bare, then reinforced and modified with a laid-down rear shock setup. It was also adjusted and smoothed to accommodate a Bright Logic x Beater GS aluminum tank.

At the rear, a GS-style tail cowl by Ohno Speed was added, and the seat was custom-formed from the base to match both the cowl and fuel tank. The Katana's stock single-unit gauges were replaced with a KZ housing, into which STACK speedo and tach units were embedded, bringing the layout closer to that of a GS.

The stem is a one-off replica of the Suzuki factory part from those days, paired with YOSHIMURA KYB φ40mm front forks. The swingarm comes from the Suzuki RGB, a GP500 racer and the wheels are KATANA-specific DYMAG magnesium.

With this level of specs, you’d be forgiven for thinking this is a full-blown AMA Superbike racer. But that’s where Nakagawa’s philosophy shows through. This bike isn’t meant for a few laps on a closed track. It’s built for the street—where pavement conditions vary, and maintenance intervals need to be practical. So while the stem looks like a race-spec replica, its dimensions and wall thickness have been reinforced for durability. The early-model AP pull-type front master cylinder has been updated with switch mounts and brackets that prioritize safety.

This GSX1000S was built with originality in mind, while also making sure it can get you home no matter what. It might feel too special to take on a touring ride but you’d have a blast doing it. And one thing's for sure: wherever you go, this bike will turn heads and spark conversations.

Handlebar

The handlebar setup is custom-made, modeled after a Suzuki works replica. The stem’s wall thickness was carefully considered for strength. A KZ meter case holds two STACK gauges: the 3082 speedometer on the left and the ST200 tachometer on the right, with a KATANA ignition key in the center. The front brake uses an AP CP4125-2 pull-type master cylinder (a system where pulling the lever draws fluid from inside the master cylinder to push the brake calipers), paired with titanium mesh brake lines like those used by Suzuki’s factory team.

Bodywork

The fuel tank is a GS aluminum tank made by Bright Logic in collaboration with Beater. The seat cowl is a GS1000 FRP tail cowl by Ohno speed, painted by Rods Design. The seat is a Katana seat, reshaped to match the tank and tail section and finished with a classic tuck 'n roll stitching style.

Engine

The engine has been fully overhauled, then fitted with custom-made forged pistons for street use from SOHC Engineering, increasing displacement to 1015cc. It also uses YOSHIMURA camshafts. Internal porting work and a high-flow oil pump gear were added, with plenty of AMA-style mods that enhance both performance and looks.

The ignition system uses an Uotani SP-2 with a custom MOSFET regulator. The main wiring harness is a brand-new one from Ohno Speed.

The carburetor is a TMR 38mm, paired with a YOSHIMURA Titanium Cyclone exhaust and a US Yoshimura silencer.

Chassis

The rearsets are custom-made and mounted with simple brackets. The lithium-ion battery (stored under the seat) is from SHORAI.

The front forks are rare YOSHIMURA KYB 40mm forks, which are not available commercially. The front brakes use AP CP3485 CNC-machined monoblock calipers and custom 310mm SUNSTAR Neo Classic brake discs.

The rear brake setup includes an AP CP4226-2SO caliper and a SUNSTAR Trad disc. Instead of a GSX-S part, one from the Z was chosen because its riveted look better fits the build.

The rear suspension uses rebuilt and re-tuned FOXSHOX shocks, the same type used in AMA Superbikes back in the day, matched with a swingarm from the RGB500, a WGP race machine. The wheels are made of magnesium by Dymag, custom-sized (2.75-18 front, 4.00-18 rear) to match the bike’s chain alignment.

Gallery

Specifications

Original Source of this Article

Heritage & Legends