This Kawasaki GPZ900R Ninja had been a faithful companion to its owner for years. During that time, the bike had made many visits to the AC-Sanctuary workshop for customization, repairs, and servicing. But the owner was always left wanting for more. So, when the planets finally aligned, he tasked Hiroyuki Nakamura and his team at AC Sanctuary with transforming the Ninja into a bonafide RCM (Radical Construction Manufacture).
The Kawasaki GPZ900R, introduced in 1984, holds a legendary place in motorcycle history, and for good reason. The combination of raw power, innovative technology, and sleek design made it stand out amongst its competitors. It was the world’s first production bike to feature a liquid-cooled, 16-valve inline-four engine; a game-changer for performance motorcycles. Generating 115 horsepower and capable of speeds over 150 mph, the GPZ900R set a new performance benchmark.
Before the release of the GPZ900R Ninja, large-displacement motorcycles often struggled with agility, but Kawasaki managed to strike a perfect balance. The GPZ900R’s lightweight frame and carefully designed suspension allowed it to carve corners with precision. The GPZ900R also gained fame outside motorcycle circles thanks to a cameo in the 1986 movie Top Gun as Tom Cruise’s steed. Decades after its release, the GPZ900R remains a sought-after classic, with collectors and riders alike praising its mix of performance, style, and history. This makes modifying a GPZ900R somewhat of a contentious topic, but if anyone is going to do the job right, it would have to be AC Sanctuary.
Every project involving old motorcycles comes with surprises. In this case, deeper inspection of the bike’s engine revealed a problem that couldn’t be ignored. Rather than push forward with the original plan, the team set about overhauling the engine. This changed the project from a standard RCM build to an RCM Type-R, which is a conversion package AC Sanctuary has developed specifically for the GPZ900R.
After hearing the news about the engine, the owner had a few requests of his own. Wiseco pistons and Yoshimura cams were at the top of the list. The fitment of the new pistons bumped the total displacement to 972cc, and the crank, camshaft, and cylinder all underwent precise modifications for peak performance. Internal friction reduction surface treatments like WPC and DLC were also used for durability. A quartet of TMR-MJN38 carbs fed by a Pingel fuel cock ensure the inline-four gets all the go juice it needs, while a Nitro Racing wide radiator and high-mount oil cooler keep things cool. Of course, no custom build is complete without a serious exhaust. Here’s it has come in the form of a Nitro Racing hand-bent titanium system, capped off with a matching Grenade V-3 silencer.
In most cases, a Type-R conversion involves updates to the GPZ900R electrical system, but here, the original components were in solid shape. So rather than a complete replacement, work was limited to areas that needed attention. It was a flexible approach that saw the engine overhaul taking priority.
To further enhance the Ninja’s already excellent handling, Nakamura-san and his team have developed a tried and tested suspension setup for the GPZ900R. At the pointy end of things, you’ll find a Sculpture steering stem kit with a set of Öhlins 43mm forks sitting in it. In the rear, there’s a Sculpture wide swingarm to allow the fitment of a sportier 180-wide rear wheel. The rear suspension was also upgraded using an Öhlins shock to ensure the bike can handle whatever the road throws at it.
When it came to the wheels and brakes, performance was once again paramount. OZ Racing Gass ZRX wheels have been paired with Brembo 4POT calipers up front and a 2POT in the rear. Pirelli Diablo tires front and rear, sized 120/70-17 and 180/55-17, offer ample grip in all circumstances.
To complete the RCM transformation AC Sanctuary has performed a laundry list of styling and accessory tweaks. Topping the list is a selection of Nitro Racing components including a front fender kit, rear set footpegs, a tinted windscreen, and a beefy belly pan. A Daytona RCM concept handlebar is perched above the tricked-out dash that houses a plethora of gauges from Defi and a digital gear indicator. There are also new fasteners, hoses, and brackets throughout to replace the tired factory equivalents.
It goes without saying that the paintwork on this Ninja, from the engine to the bodywork, wheels, and chassis is all new. AC Sanctuary go-to painter Okushin laid the slick black and red scheme, adding period-correct decals to complete the bike’s racy look. With its slick paint scheme, carefully curated blend of high-performance parts and quality accessories, this RCM Type-R GPZ900R is a cut above the rest. AC-Sanctuary has once again created something truly special that goes well beyond a fancy facade. It’s no wonder their considered one of the world’s best resto-mod shops.
