For millions of people around the world, a motorcycle is a form of transport, nothing more. Then there are those of us who have a passion for all things two-wheels, we’ve gone well past the hobby phase and find it very easy to justify owning more bikes, buying more parts and spending longer in the saddle. But then there are those like the owner of this incredible motorcycle, whose addiction simply has no cure. Most would give their left arm to own a single AC-Sanctuary RCM (Radical Construction Manufacture) creation, well our friend from Japan owns four and yet he just had to have another one. So, Hiroyuki Nakamura and his team got to work, building for their client his most radical ride yet, a Kawasaki KZ1000 MkII, with the special designation, RCM-600.

The Chiba-based company has become quite used to repeat customers, with many opting to have their second bike built in a more extreme manner. And hey, if you can afford it, why not? Owning one RCM for the road and one for the track is many people’s dream, but Nakamura-san was humbled when his client returned for his fifth full custom build. It was for this reason that he chose to skip the usual numbering system which is assigned when each bike starts its transformation, and instead give a simple, round number, in RCM-600 to this very deserving customer. The donor bike was easy to source, it came from a collection the company had stockpiled for future builds, so work could begin immediately.

“This large-scale vehicle was produced as a specification with a strong personality at the request of the owner. In particular, we have been asked to be uncompromising on the visual aspects,” Nakamura-san tells us. And the visuals sure do hit strong, for a motorcycle that is 100% road-legal, this Kawasaki has all of the wow factor you would normally associate with a track-only special. Starting at the very front of the bike, the headlight cowl is that signature MkII style, with extra relief cut out to ensure no fouling on full lock and a classic smoked screen to finish it off. Below the front fender is made from carbon fibre to keep the weight incredibly low, and is from the in-house Nitro Racing catalogue.

The fuel tank is a hand-crafted work of art, more lightweight materials are employed and the shoulders are widened to give a more beefed up appearance. A breather is neatly fashioned into the top of the tank and a single race-style filler completes the look. Underneath the engine, a fully functional belly pan not only hits the track bike aesthetic but is designed to catch and hold the oil should the engine let go. And nothing is more track orientated than the full TOMO FRP single-seat cowl, as used by the AC-Sanctuary track bikes when they race at the famous Tsukuba TOT. The paint job, well that simply speaks for itself, with the graphics package tying the look together perfectly.

But if Nakamura-san was truly going to deliver for his special client, he had to give him even more and for something truly special, you only have to look at the Sculpture swingarm to see a little extra going on. The part is officially known as an “Eccentric Adjuster Type Rear Suspension Mount & Stabilizer”, yes Nakamura-san admits it’s a long name. But this parts package was first developed for RCM-001 and now all these years later makes a comeback. Essentially by loosening off two nuts, you can adjust the mounting angle of the rear shocks, which when combined with that alloy swingarm and the fully adjustable Ohlins shocks, gives incredible scope for fine-tuning.

The front end doesn’t let things down either, and wanting to maintain the period look, the forks are traditional in their style and developed with Ohlins to create the “E x M” package. A fork brace adds additional stiffness and then a complete set of one-off triple clamps was machined to complete the conversion. Everything from the frame to the suspension is designed to work with a 17-inch wheel, front and rear, and the Oz Racing rims look stunning in gold, all wrapped up in Pirelli Diablo Rosso 4 rubber. As always the braking is a combination of modified Sunstar and Brembo items, with the front calipers being the racing-derived GP4-RX radial units.

But this bike is about more than just looking good and having the best bits, it’s also bloody fast! To achieve the speed all involved desired, a good condition block was stripped, machined, given new liners and then bored out 5.6mm over standard to achieve a capacity of 1135cc. Leaving the stroke factory allows the engine to rev hard, and to speed that process up, a set of lightweight forged pistons are matched to a CNC machined crank. The top end is out of this world, absolutely no part is standard, with the entire valve train upgraded to the latest and greatest pieces, which are then bumped by a set of Yoshi cams. The transmission is built to the same spec as the AC race bikes and the clutch is now based around the more sturdy Z1000 Police Special housing.

Of course, the bolt-on bits are just as juicy, with a full bank of Yoshi carbs supplying the fuel and the famous in-house full titanium Nitro Racing exhaust spitting flames on the over-run. To allow the team to really dial things in, a fully programmable electronic ignition is also part of the package and temps are kept low with AC’s own oil-cooler kit. But the one-off custom work doesn’t end there, Nakamura-san has ensured a never to be repeated dash was crafted, using a mix of Stack gauges and OEM idiot lights, all mounted on carbon fibre.

And from the bars, to the rearsets, and the radial master cylinders, every last part is simply as good as it gets. The owner couldn’t be more happy, with his fifth RCM his favourite. But as if to prove the point, he’s just placed an order for number six, and this time it will be a Honda based beast to keep his brilliant Kwaka’s company.

[ AC Sanctuary ]