860cc Kawasaki Z2 Restomod

RCM-617 from AC Sanctuary, inspired by Aitsu to Lullaby…  

Most of us know the story of the Kawasaki Z1. Introduced in 1972, the 903cc UJM superbike was the fastest and most powerful Japanese four-cylinder ever produced at the time, upstaging the CB750 and birthing the iconic Kawasaki Z series.

However, have you ever heard of the Z2? Also known as the Z750, the Kawasaki Z2 was a 750cc version of the Z1 designed for the Japanese domestic market, which mandated a maximum capacity of 750cc at the time. Here in North America, we seldom got to see these bikes except for rare examples brought home by returning servicemen.

To build the Z2, chief engineer Ben Inamura and his team didn’t just sleeve down the 900 and call it a day. They actually spent an additional six months of development on the home-market 750.

“The new Z2 had a 64mm bore x 58mm stroke (versus the Z1’s 66mm x 66mm), a redesigned crankshaft, and smaller, 26mm carburetors for an output of 69 horsepower at 9,000rpm. The rear sprocket had 42 teeth instead of the 35-tooth Z1 item, but aside from the sprocket, most of the cycle parts were the same as the Z1…” –Motorcycle Classics

The Z2 quickly became the most popular big-bore bike in Japan — so popular, in fact, that it found its way into many popular manga series, including Great Teacher Onizuka and Aitsu to Lullaby. The latter series goes like this:

“On a Wednesday morning, Kenji goes touring to Hakone pass with his girlfriend Tomomi. There, he sees other riders waiting for something and stops his bike. One of the riders, Hayase Junichi, explains to him that a legendary female driver nicknamed Wednesday Cinderella passes this place every Wednesday in her white Porsche. Kenji becomes interested in this mysterious driver; however, racing with her proves more dangerous than it first seems to be.” –My Anime List

This manga was very popular in Japan, and many readers fell in love with Kenji’s custom Kawasaki Z2. One of those readers was none other than Hiroyuki Nakamura, founder of AC Sanctuary:

“All of the manga were hits and everyone was fascinated, and I remember reading them enthusiastically. The manga about riding a Z2 is surely memorable to many motorcycle riders.”

The machine you see here — RCM-617 — is inspired by the Z2 from Aitsu to Lullaby, built in one of the world’s most revered workshops. The project didn’t begin as a full blown RCM (Radical Custom Manufacture) build — a title reserved for AC Sanctuary’s most exclusive and extensive builds. However, it soon evolved…

“Initially, we were entrusted with a Z2 owned by an owner who wanted us to customize and restore the frame, suspension, engine, and other important parts, but as the work progressed, we felt that it was appropriate to treat it as an RCM, and we decided to attach a serial number.”

Interestingly, they decided to keep the bike on 18-inch wheels instead of converting it to 17-inch specification, as is standard operating procedure with most RCM builds. Says Nakamura-san:

“Actually, I personally felt that the Z2 in the comics that served as the model was a 17-inch wide wheel specification. Not only the Z2, but other machines that appear in the comics, such as the 750SS and Katana, have thick tires due to the deformation of the manga. That’s another cool image, but the fact that the rear tires of all the machines look like they’re 180 is just my opinion.”

However, nostalgia won out in this case, and the bike is equipped with 18-inch PMC Sword wheels (2.75″ front, 4.0″ rear) and Continental Road Attack 3-CR tires. The frame was given a stage-1 reinforcement, and the suspension and brakes upgraded with Öhlins 18-inch ExM front forks, Öhlins Legend Twin rear shocks, Sculpture swingarm, and Brembo calipers.

The engine was fully rebuilt, bored to 860cc with Wiseco pistons, PAMS liners, 36mm Yoshimura Mikuni TMR-MJN carbs, Nitro Racing oil cooler, AS Uotani SP-II ignition, and slipper clutch. While not as radical an engine build as some of the other RCM builds, it’s fast-revving and streetable, with plenty of ponies on tap.

The handlebars, yokes, and dual gauges were all designed to recreate the Z2 from the comic with no sacrifice in performance or handling. As the model was type-certified as a 750 under Japanese law, AC Sanctuary actually had to apply to make certain structural modifications.

We don’t normally get to see an AC Sanctuary restomod built to a theme like this one, let alone a JDM-specific Z2 as a donor, so it makes RCM-617 doubly nostalgic and special — especially for those who loved and lusted after the Aitsu_to_Lullaby Z2!

Below you’ll find a full-blown spec sheet and more detail shots of the build.

Build Specifications

Chassis (18 inches)

Body

Intake and exhaust, cooling, and electrical systems

Follow the Builder

Website: www.ac-sanctuary.co.jp
Facebook: www.facebook.com/ac.sanctuary

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