Two weeks can seem to absolutely fly-by, usually when you’re in some beautiful location on holiday, or it can drag on as you watch the clock on the office wall slowly tick away. But imagine how long that fortnight would feel if you were meant to get your dream bike delivered a few days before Christmas and then at the last minute were told you’d need to wait until the new year. Well, Mr K, from Japan’s Kochi Prefecture, had to suffer that kind of agony, but you simply don’t get your AC-Sanctuary motorcycle until supremo Hiroyuki Nakamura is satisfied it’s perfect. And that’s the only way to describe the Resto-Mod King’s latest build, RCM-609, a Honda CB900 with all of the sweetest fruit.
Truth be told, Nakamura-san was more disappointed than anyone that there was even a small delay with delivery, he’s built more than a thousand custom motorcycles and race bikes and is always on time. He also explained some of the unique problems when working with the ageing CB900F platform, “Most of the important consumable parts inside the engine are out of stock from the manufacturer, so it takes a long time to find and obtain those parts. It is clearly more difficult than it was about 10 years ago, and it will probably become even more difficult in the future.” But even with those factors taken into account, it was a part that cost less than $10 that forced Mr. K to wait a little longer.
But before we get to that point, you have to go back to the start of the build, when an excellent condition Honda CB900F was rolled into the AC-Sanctuary workshop. Even as quality donor bikes become harder to find, and builders are forced to work with some true piles of junk, this Honda was nothing of the sort. You could have literally eaten off the Keihin carb tops and there was no sign of oxidisation on the engine or the usual localities. But, there was no time for nostalgia, the perfect condition 40-year-old CB was pulled down to a bare frame and then placed into one of the workshop jigs. From here one of the lead fabricators ensured the factory steel frame was millimetre straight.
Then the grinder was fired up to smooth out a lot of the stock welds, lay down some more beads where they were needed and begin the process of the AC chassis transformation. This involves adding larger steel mounts around the centre post, gusseting the headstock and adding further bracing around the swingarm pivot point to ensure the old girl could handle the extra forces coming her way. Speaking of swingarms, the unit chosen is a relatively mild piece for the resto-mod gods, but the in-house constructed Sculpture “wide” arm allows for bigger rubber to be fitted, is seriously lightweight and looks brilliant in polished alloy.
Playing with the geometry and the rider height and weight, Nakamura-san decided that the best results would come from changing the mounts for the rear shocks, moving the top eye of the Ohlins units down just a tad. The front end also wears the gold of Ohlins, with a Sculpture steering stem allowing the fully machined and anodised triple clamps to bolt to the stock Honda neck. The conventional forks use a clamp-style brace for additional rigidity and custom CNC’d brackets have been made to mount up the Brembo calipers, with AC-designed Sunstar discs. A set of 17in Oz Racing wheels deliver the goods and the bike was rolling.
Front to back, the bodywork is absolutely flawless and retains an enormous amount of the stock components to deliver that signature twin-cam CB silhouette. Normally not a fan of side covers that merge with the fuel tank, Nakamura-san loves the Honda look, and each piece has been panel beaten to perfection. A new set of factory graphics was acquired before the bike was sent into the paint booth and the owner chose to retain the original red colour scheme. The front guard is the only truly new piece of panel work but teamed up with the stock taillight and a traditional headlight, and the look takes you right back to the ’80s.
“The handlebar is an RCM concept bar released by Daytona. The left and right grip ends are also RCM concept grip ends, that can be fixed with bolts to prevent vibrations,” Nakamura-san tells us. And all that was left to do before taking care of the engine was to bolt on the custom rearsets and set them up for Mr K. Despite the perfect condition of the cases, the client wanted the engine blacked out, so these have all been cleaned up of polish and chrome and hit with a heat proof paint. The internals get a full rebuild, with no seal, gasket or even bolt left unreplaced, and the clutch and gearbox come in for a full overhaul too. Essentially you get as close to a new bike as possible.
Now with that beautiful lump bolted in, the exhaust could be fabricated, the headers are the company’s bolt-on Nitro Racing Weldcraft 3D titanium pieces. But the rest of the system came in for a change, as it was felt the remainder of the pipework should run tighter to the engine than usual, before sweeping up into the Nitro muffler. Finally, the bell mouthed breathing Yoshimura Mikuni TMR-MJN36 bank of carbs go on, and the bike was complete.
But Nakamura-san always gives the bike a thorough test ride before final delivery. And here comes the delay, the jetting just wasn’t right, despite adhering to the usual specs. So, with a fresh pair of eyes, the boss came back to work after the holiday break, and with no less than ten jet sizes in hand, he got the big CB dialled in to perfection and could finally let Mr K end his arduous wait for the bike of his dreams.
[ AC Sanctuary ]