Built on a Solid Foundation: KAWASAKI GPZ900R Custom by SANCTUARY

SANCTUARY's GPZ900R

AC Sanctuary has long been known for their RCM (Radical Construction Manufacture) project, creating many expertly crafted customs based on the GPZ900R Ninja. One of their signature plans, the RCM Ninja Sport Package New Type-R Start Edition, features a fully overhauled engine and a chassis optimized for 17-inch wheels—earning it a solid reputation among fans as the ultimate evolution of the Ninja.

Building on that New Type-R foundation, this RCM-580 takes things even further with additional customization. The standard TMR carburetor has been upgraded to a TMR-MJN unit with dual stack funnels, refining both looks and performance.

With the New Type-R package, base bikes are built with an emphasis on maintaining consistent quality. That said, finding good base bikes has become increasingly difficult in recent years. In particular, engine internals like camshafts and rocker arms now often require immediate replacement due to wear. When building an RCM, the engine is pressure tested by AC Sanctuary’s in-house machining division, DiNx, to ensure it is sound. But recently, they've encountered more cases of coolant leaks around the wet liners, caused by a specific O-ring used between the sleeve and cylinder. Of the two O-ring types required, one has already gone out of production, raising concerns about future parts availability.

For this RCM-580, extensive engine work was carried out to ensure peak performance—this included correcting crankshaft runout, dynamic balancing, and journal wrapping. The result is precision and finish that surpass even factory-new standards.

Mr. Nakamura from AC Sanctuary explains: “To keep offering the New Type-R, we want to handle as much of the part supplementation in-house as possible.” The RCM-580 stands as a testament to that commitment—a modern-day Ninja built with expert craftsmanship, reliable performance, and enduring passion.

Handle

The brake and clutch master cylinders were upgraded to Brembo RCS units (the standard New Type-R setup uses horizontal NISSIN ones), while the mirrors were replaced with Magical Racing’s Racer Replica mirrors (Type 2 heads). The striking placement of the A6-style GPZ logo was a specific request from the owner.

The front end uses the SCULPTURE Stem Kit Type-1, which changes the offset from the stock 40mm to 37mm. The handlebars are DAYTONA's RCM Concept Low Handlebars. The stock gauges were refreshed, and a YOSHIMURA PRO-GRESS Meter was added.

Bodyworks

The exterior was repainted by Okushin based on the stock A6 color, with additional custom touches like the logo colors and the Kawasaki emblem to give it a more refined look.

The seat is DAYTONA’s RCM Concept COZY Seat, designed with comfort and fatigue reduction in mind.

Engine

The engine has been big bored to 958cc using φ74.5mm forged pistons. The crankshaft has undergone correction for runout, dynamic balancing, and journal wrapping. Around the cylinder head, the full treatment includes installing oversized valve guides and seat cutting. The engine exterior is finished with a durable Gun-Kote coating. The frame has been modified to suit 17-inch wheels and a wider rear tire, and a NITRO RACING Combination Kit III has been added. The main nut that secures the rearsets at the swingarm pivot features a MENACHITE titanium nut.

The carburetor is a Yoshimura TMR-MJN φ38mm with Dual Stack Funnel (DSF) configuration. The dual-stack funnels are finished in gold and black to match the body color.

Chassis

The front forks are OHLINS RWU forks from the NOBLEST ExM package. The front brake setup pairs Brembo 484 calipers with a radial mount and bridge layout, with 320mm SUNSTAR RCM Concept discs.

At the rear, an OHLINS KA203 shock, designed for 17-inch compatibility, is paired with a SCULPTURE wide swingarm built specifically for RCM machines. The drive chain is a narrow-body EK530RCM from EK Chain, finished in black and gold.

The rear brakes consist of a Brembo 2-piston caliper paired with a SUNSTAR Premium Racing Disc φ250mm / Hole & Slit Type. Both front and rear wheels are forged aluminum OZ Racing GASS RS-A, sized 3.50-17/5.50-17. The exhaust system consists of a heat-colored NITRO RACING titanium exhaust and a Grenade Titanium V-II Silencer.

Gallery

Specifications

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

SANCTUARY brand page

Original Source of this Article

Heritage & Legends