RCM-604 by AC Sanctuary…
When the Honda CB900F first appeared in 1979, it wasn’t available in the States, as Honda was worried it might steal the thunder of the mighty CBX. American riders grew green with envy at images of European riders hustling the 901cc superbike through the winding roads of the Alps and Pyrenees.
The six-cylinder CBX might have boasted a higher top speed, but on a track or canyon road, the CB900F would be the clear winner.
“A thundering Super-Sports bike with devastating performance and an unwavering stamina.” -Honda
The CB900F was a direct descendant of the CB750F, featuring exotic technology for the era: four cylinders, dual overhead cams operating four valves per cylinder, and the cams linked to the crank by two silent-type cam chains. Max output was 95 horsepower at 9000 rpm — just 10 ponies down from the heavier CBX.
The CB900F would run the quarter-mile in the elevens, and by the time it reached US shores in 1981, top speed was clocked at 130+ mph. In 1982, Fast Freddie Spencer and team trounced the competition for a podium sweep in the Bell Superbike 100 at Dayona.
But the advent of liquid-cooled, aluminum-framed sport bikes was nigh, making the CB900F the height of a certain breed.
“The ultimate statement of the old air-cooled technology Honda had done so much to create.” -Kevin Cameron
Enter Hiroyuki Nakamura and his team from Japan’s AC Sanctuary, builders of the baddest Japanese restomods on the planet. While Nakamura-san is best known for his Kawasaki Zed and Ninja builds, he’s also brought his particular set of skills to the Suzuki Katana and Honda CB-F series, such as the CB1100F we featured a couple of years ago.
With these RCM (Radical Custom Manufacture) builds, every facet of the original machine’s performance is upgraded: power, suspension, brakes, wheels, rubber, etc.
“As old bikes, customization and tuning can improve their dynamic performance, and the obvious difference in performance changes is a big attraction.” -Nakamura
For one of his latest and most time-consuming builds — RCM-604 — the owner chose the mid-displacement CB900F from the CB-F series. The chassis was stretched, straightened, reinforced, and repainted, while the wheels were switched to OZ Racing 17-inchers to accommodate modern rubber — Pirelli Diablo Rosso IV tires, to be exact.
The bike is now running 43mm Öhlins forks with Brembo dual-disc brakes and more Öhlins suspension in the rear. The rear swingarm is a billet Sculpture piece, an RCM exclusive produced in-house. While exotic, such trappings are to be expected for any RCM build.
But problems began to arise when it came time to overhaul the engine.
“The manufacturer’s stock is decreasing year by year, and the situation is getting tougher. Even though engine overhauls require internal combustion engine processing, it is difficult to replace consumable parts. In order to improve the completeness of the overhaul, it can be said that procuring new parts is the biggest challenge.” -Nakamura
In order to make the owner’s dream come true, Nakamura-san’s team spent hours “staring at auctions and overseas parts sites,” trying to find the consumable parts necessary to carry out the rebuild.
He says the issue is the same for any CB-F, CB1100R, or CBX1000, but ultimately it depends on the owner’s strong desire to make it happen.
“This is because without passion, it would not have been possible to make it, with a long production period of a year or with a sense of cost for parts that are difficult to obtain. The owner of this RCM-604 had exactly that kind of feeling, which is why he was able to make it happen. RCM for the CB900-F, which is obviously more difficult to obtain parts for than the air-cooled Z series or Ninja series. It has been reborn with modern specs and is still able to run well today.”
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More AC Sanctuary Restomods…
Thundering Super-Sport: Honda CB900F Restomod - RCM-604 by AC Sanctuary… When the Honda CB900F first appeared in 1979, it wasn’t available in the States, as Honda was worried it might steal the thunder of the mighty CBX. American riders grew green […]
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Resto-Monster: Honda CB1100F Restomod - 1123cc Honda Restomod from AC Sanctuary… In 1983, the Honda CB1100F arrived as the company’s king sport bike, designed to battle head-on with the 1100-class superbikes from Kawasaki, Suzuki, and Yamaha — bikes that were […]
Monster Zed: Kawasaki Z1-R Restomod - AC Sanctuary’s “Radical Construction Manufacture” Z1-R… In the world of high-powered Japanese restomods, one name has long stood apart: AC Sanctuary. Founder Hiroyuki Nakamura opened his shop in the 1990s. Since then, they’ve built a […]