Not everything is always as it seems, and if you judge this book by its cover, then you are probably assuming it is simply another in a long line of incredible Z900 custom builds by Japan’s masters of the Resto-mod, AC-Sanctuary. But this incredible Kawasaki started life in a very different state to the usual flawless donors selected by head honcho Hiroyuki Nakamura. The differences to a normal AC build don’t stop there, with this machine benefitting from the success of the company’s current racing program, and the final twist? It’s not actually a 900 at all, but a killer KZ1000 that’s been given the stunning looks of its little brother and the performance to take on the most modern of machines.
In recent years Nakamura-san has explained to us the difficulty in finding donor bikes for his company’s amazing custom builds. It is not only the price that has soared to insane amounts, but good condition examples of the ’70s best sports bikes are few and far between. He’s made a number of trips to Europe and the USA to collect as many bikes as he can for future customers, but on this build, he was prepared to instead use the client’s current ride. Unfortunately for the said client, they’d already spent considerable sums of money elsewhere having their KZ1000 heavily modified, only to take home a less than satisfactory bike with a noisy engine, and poor performance.
So, there was only one thing for it, the bike would once again be stripped back to its barebones, but this time it would be built properly and to the highest of standards. The frame was placed in the jig and a host of modifications were made to first set up the bike to run on 17in rims front and rear and then to ensure that the chain alignment was spot on.
Then the guys perform what they call an ST-II reinforcement treatment to the chassis, with extra gussets welded in, the area around the headstock given a serious amount of extra metal and the swingarm pivot points upgraded. Before the famous alloy Sculpture swingarm was fitted in place, and there is simply no other product like it for the Z.
One of the huge advantages of having AC-Sanctuary build your bike is that they have experts in every area of a motorcycle. And with the engineers working on the frame, the rattling KZ1000 engine was over being rebuilt by the mechanics. These are the same guys who screw together the company’s Z race engines, which showed recently how powerful they are at the recent Taste of Tsukuba event, where they kept pace with modern water-cooled machinery. This engine has been prepared to a similar spec, with a fully refreshed block filled with a new crank and forged pistons that take capacity out to a thumping 1166cc.
The cylinder head comes off the flow bench and is filled with all of the best bits, from Kent ST high lift cams to a full race-style valve train which not only provides for enormous gas flow but allows for extended periods of high rpm running. To stuff the package full of air and fuel, the team’s carburettor of choice is the Mikuni TMR MJN dual stack 38, tuned precisely for this combination.
On the exhaust side of things, you won’t find many better than the handbuilt titanium system with a Nitro racing muffler. The rest of the package would take a novel to describe, but from the ignition to the clutch and new 6-speed gearbox, and all the electrics, nothing goes untouched.
Meanwhile, over in the body shop the boxy look of the KZ1000 was being swapped out for the beautiful lines of the earlier 900 model. And the look is kept traditional and serves as a serious contrast to the radical mechanical makeover. A Doremi Collection fuel tank is perfectly placed over the backbone, but without a doubt, the signature look is created by the side cover and tail cowl combination. Given the wheel size change, one of AC’s own front fenders is fitted up and then the whole lot is hit with a solid black, with original Kawasaki badges placed over the top.
The rolling stock is vital for performance and in the OZ Racing Gass RS-A wheels, the Z gets the lightest set of 17in rims that are legal in Japan for road use. The suspension package that supports them is simply as good as it gets and the Ohlins front forks are held in place with in-house machined triple clamps and the company’s own steering stem, which Nakamura-san feels is a too often overlooked component. At the rear, the twin shocks are from the Ohlins Blackline range, which are rebuilt to exacting standards, and do their best to help the big 190-section Pirelli tyre maintain traction with all that torque coming down the line.
The braking package is a tried and true combination that AC fits to most of their bikes and starts with huge Sunstar RCM discs built for Nakamura-san’s creations. These are clamped by radial mounted Brembo GP4 calipers with power coming from a Brembo 19RCS master cylinder. The rear is not quite as extreme, with Brembo and Sunstar providing the goods and a Nitro Racing rigid caliper support for a solid feel. To finish out the build, the factory gauges are rebuilt and big round mirrors help to maintain that ’70s vibe. But to give this extreme KZ1000 a touch of visual aggression, the taillight and indicators are tinted.
There was nothing conventional about the way this bike commenced its AC-Sanctuary journey and yet it leaves the workshop as yet another roided up, rampaging resto-mod that has no rivals in the power package.
[ AC Sanctuary ]