RCM-554: 1165cc Zed from AC Sanctuary…
The Kawasaki KZ900 was the direct successor of the mighty Z1. On the time of its introduction in 1972, the unique 903cc Zed was the biggest, strongest four-cylinder Japanese bike ever made — a real alpha bike:
“With brutish, swooping traces and quad pipes clutching an impressive engine like a black coronary heart in an iron fist, the Z1 was an archetype of menacing model. Natty in its distinctive sweet coloration scheme, the massive Kawasaki seemed like a heavyweight boxer out for an evening in town…” –Final Motorcycling
Launched in 1976, the KZ900 was primarily an up to date Z1, that includes smaller 26mm Mikuni carbs, thicker-walled body tubing, a locking fuel tank, and completely different facet covers and taillight design. Regardless of these refinements, the KZ900 was nonetheless a beast:
“Tuning alterations and smaller carbs shaved a couple of watts off the powerplant in an effort to refine the bike’s uncooked grunt, however driving a KZ900 at this time precipitates a case of adult-onset Deja Vroom.” –Final Motorcycling
For those who’ve been following BikeBound for very lengthy, you already know we’re huge followers of Japan’s AC Sanctuary and their RCM (Radical Customized Manufacture) collection — a lineage that incorporates a few of the baddest air-cooled Japanese restomods on the planet.
Although most of RCM’s orders used to come back from Japan, the AC Sanctuary title is now identified and revered everywhere in the world. Founder Hiroyuki Nakamura says they now obtain 1-2 orders yearly from abroad.
This one got here from a German engineer and shopper who despatched over the KZ900 body, which acquired RCM’s “Stage II” body reinforcement and alignment, utilizing RCM’s in-house jigs.
In the meantime, the engine was rebuilt with a high-compression 1165cc Wossner piston package, Yoshimura ST-2 cams, outsized valves, ported and polished heads, and a 13-stage oil cooler with high-pressure pump.
Like most all RCM builds, this “KZ1123” is rolling on Öhlins suspension, OZ Racing wheels, and Brembo brakes. Says Nakamura-san:
“As you already know, these three producers’ merchandise are actually the world’s highest high quality manufacturers, and they’re the one prime class merchandise appropriate for RCM. It’s a stable undercarriage.”
For the reason that body got here from Germany, the AC Sanctuary staff couldn’t legally experience the completed bike on Japanese roads, so that they rented a brief circuit for testing functions — speak about dedication!
Under, we hear the complete story on the construct.
RC-554: Within the Builder’s Phrases…
It’s not uncommon now to obtain an RCM order from abroad. Yearly, about 1 to 2 orders. It’s the present scenario that RCM builds are at all times being produced on the premise of export. The serial quantity guidelines stay the identical. Like Japanese customers, there’s a singular serial quantity that doesn’t have an equal anyplace. A key holder bearing the serial quantity is handed over, and regardless of how far-off the bikes goes, it’s a real RCM.
This RCM-554 is constructed on a body despatched from a German proprietor. The bottom chassis is the KZ900, which is extra developed than the Z1. The KZ900 was chosen based mostly primarily on the body. It’s nonetheless an air-cooled Z, with an angle that pursues efficiency, which is in accordance with the idea of RCM.
The engine displays this angle. We started with a rebuild of the crankshaft and the TW firm’s 6-speed cross transmission. From the proprietor’s residence nation of Germany come the Wossner pistons, a excessive compression bundle — an enormous bore with twin spark plugs. The engine has a pointy deal with tuning, with Yoshimura ST-2 camshaft, huge valves, and port sprucing.
In fact, including this a lot will have an effect on the lifetime of the engine, so it’s important to equip it with an oil cooler, and a trochoid rotor-type high-pressure oil pump is an indispensable merchandise to reinforce the oil cooler operate. Partly as a result of the proprietor himself is an engineer, this half selection was determined with out hesitation.
The body that receives the power-up engine is Sanctuary’s authentic body reinforcement STAGE-II. Excessive-precision manufacturing utilizing numerous particular jigs equivalent to rear suspension laydown and in-line processing to safe the drive chain observe. It’s an intricate body.
The undercarriage fitted to such a body is a masterpiece from the world’s prime producers: a mix of Brembo brakes, OZ Racing wheels and Öhlins suspension. As you already know, these three producers’ merchandise are actually the world’s highest high quality manufacturers, and they’re the one prime class merchandise appropriate for RCM. It’s a stable undercarriage.
Since there isn’t a strategy to change the efficiency of particular person components, it’s at all times the very best at RCM. It may be stated that this can be a widespread feeling not solely in Japan but in addition on the earth.
As a result of RCM-554 is predicated on the body despatched from Germany, it can’t be registered in Japan, and a highway take a look at on public roads isn’t attainable. For that motive, we’re renting a brief course and doing a highway take a look at earlier than exporting.
As for the language barrier when ordering from abroad: Though there are some difficulties, we wish to present our willingness to reply so long as there are requests from abroad equivalent to “I need RCM!”
Chassis (17 inch wheels)
|Tandem step||NITRO RACING TYPE-2|
|Sheet||DAYTONA RCM CONCEPT COZY SEAT|
|Clutch Grasp||Brembo RCS radial clutch grasp|
|Drive sprocket cowl||NITRO RACING NEW clutch plate black/black|
|Clutch hose||Allegri Quick System|
Air consumption/exhaust/cooling/electrical system
|Ex muffler||NITRO RACING Titanium Hand Bent Full Exhaust Warmth Polish|
|Silencer||Grenade Titanium VIII Warmth Polish|
|carburetor||MIKUNI YOSHIMURA TMR MJN 38Ф CARBURETOR DSF|
|Ignition system||AS Uotani SP2 Twin Plug Bundle|
|Cooling system||NITRO RACING 11 inch 13-speed flat oil cooler|
|Piston Maker||WOSSNER Piston 75Φ Piston Ring WPC Therapy|
|Crank||Bearing alternative full rebuild|
|Cylinder||Pamus EST Liner Boring & Palfos M remedy after honing Prime and backside surfaces are floor to a minimal worth|
|Mission||6-speed cross transmission Chainline EVO system / Dock clearance precision shim adjustment|
|Crankcase||Prime floor minimal floor grinding|
|Valve IN||Pam’s Massive Valve Φ37|
|Bulb EX||Pam’s Massive Valve Φ31|
|Valve information||Oversize valve information alternative|
|Valve seat||Oversize valve seat ring Seat minimize processing|
|Cylinder head||IN & EX Port Machining, Sprucing, Twin Plug Machining, Decrease Floor Minimal Worth Floor Grinding|
|Cam chain||EK cam chain|
|Timing components||Yoshimura light-weight adjustable cam sprocket|
|Cylinder Stud||SMB Chromoly Cylinder Stud Bolt|
|Cylinder head nut||SMB Chrome Molybdenum Nut|
|Camshaft||YOSHIMURA HIGH CAMSHAFT ST-2|
|Different||Yoshimura valve spring/Yoshimura valve seat/ Yoshimura light-weight retainer / SMB excessive strain oil pump KIT|
Observe AC Sanctuary