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Old 02-22-2016, 02:50 PM   #1
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Old School Speed!

Jon Urry

Nobuaki Harigae and the fastest GPz1100 in the world.

Jon Urry

Nobuaki Harigae of Harigae Engine Works is one of Japan’s foremost tuners for 1980s and 1990s four-stroke Kawasakis and built the two Kawasaki GPz1100 racebikes shown here for the Taste of Tsukuba series in Japan.

To the casual observer Harigae Engine Works looks like an unassuming row of garages in a Japanese suburb. Outside the series of metal-shuttered doors there is little clue as to what lies within. The eagle-eyed might pick up on the nose cone of an Eddie Lawson-replica ZRX poking out from a small pile of rubbish or even the discarded ZZR front fairing at the other end of the enclosure, but these only hint at what is hidden behind the metal doors. Tucked away in the small town of Nekozane in the Ibaraki district about an hour east of Tokyo lurks the fastest Kawasaki GPz1100 in the world.

Owned and run by Nobuaki Harigae, Harigae Engine Works ( is one of Japan’s foremost tuners for 1980s and 1990s four-stroke Kawasakis. If it has GPz, Z, or ZRX in front of a series of numbers, then Mr. Harigae can make it go very fast indeed. And to prove his skills, during the last six years he has created the ultimate GPz1100—a bike with a staggering 193 hp that weighs just 394 pounds!

“Before I started Harigae Engine Works I raced a GPz, which is why I have a great deal of affection for the bike. I know the motor and decided it was the best engine to demonstrate my tuning skills. I have a great deal of passion for the GPz, as well as the original Z1000 and ZRX,” he says.

Looking inside his workshop you can see the evidence of this obsession. Every available space is filled with a component from an inline-four Kawasaki. On the table in the center of the room rests three or four engines in various states of repair. A box of pistons sits on the floor. The shelves that surround the room are stacked full of cylinder heads, valves, camshafts, and clutches, while a complete frame hangs from the ceiling. There isn’t space to put down a cup of coffee without moving a large piece of metal first, and trying to negotiate the maze of components littering the floor without falling over is a tricky procedure. It is clear that when Harigae says he has a passion for the GPz he isn’t exaggerating; however, it is when he takes this passion and converts it into horsepower that Harigae’s work enters a whole new level.

Jon Urry

Every part and piece inside his workshop proves that Harigae has passion.

Jon Urry

Every available space is occupied by various parts that go into creating some of Harigae's masterpieces.

The GPz model we are referring to is not the original air-cooled 1100 manufactured in the mid-1980s but rather the unrelated and less-well-known liquid-cooled model offered in the mid-1990s. “The GPz1100 engine is a close brother to the ZZR motor, so there is plenty of power to be had. Kawasaki has many brother engines. For example, the ZRX is also very similar to the GPz; it has the same roots. With this engine I didn’t use any ZZR parts but instead decided to build a very powerful GPz, the most powerful I could, so it could compete in the Taste of Tsukuba race series.”

The Taste of Tsukuba is one of the best-kept secrets of the Japanese race scene. The rules are gloriously simple—the bikes have to have four cylinders and a steel frame. That’s it; anything else goes. You can tune the living daylights out of the motor, fit what you like to the chassis, even build your own if you wish, but as long as the bike has four pistons and a steel chassis away you go. Lining up against Harigae’s bike in the superbly named Hercules & Super Monster Evo class are the likes of Kawasaki ZRXs, Honda CB1100Rs, and even a Ducati Desmosedici! Racing this MotoGP replica against a field comprised of flat-bar retros might seem a little unfair, however that isn’t taking into account Harigae’s tuning skills or his dedication to success.

Jon Urry

Shelves line the walls covered with cylinder heads, valves, camshafts, etc.

Jon Urry

Parts stacked from floor to ceiling is any bike builders' dream.

“The engine started life as a GPz1100, but I increased its displacement from 1,058cc to 1,135cc with a 3mm-larger bore and Cosworth pistons,” Harigae states. “I used to use Yoshimura camshafts, but I now make them myself. And I also skimmed the cylinder head to increase the compression. This bike runs at around 13:1. I believe the original GPz1100 is closer to 10:1. I use very strong conrods! I have dyno’d the bike at 193 hp with 147 Newton-meters [108 foot-pounds] of torque.”

With the original bike making a claimed 129 hp, which in reality was only just over 110 hp on a good day, it is no surprise that this extreme tune has some side effects.

“We have a slight problem with the gearbox—the problem being I have to rebuild it after each race!” Harigae confirms with a smile. “It probably has too much power. I tried to modify the gearbox for more durability, but it didn’t help, so I decided it was better to use the conventional gearbox and just swap it. Luckily parts are not too hard to get in Japan, as the engine has so many brothers.”

Jon Urry

The shop’s logo stems from the name of the town it is located in, Nekozane. “Neko” is the Japanese word for “cat.” The text reads, “I’m going to kill you.”

Why no slipper clutch? “The rider should control the back-torque,” he replies. You would have thought that after the 10th gearbox he might have relaxed this view…

Feeding this gearbox-eating beast of an engine is a bank of 41.5mm Keihin flat-slide carbs modified slightly by Harigae, while a Honda CBR1000RR radiator attempts to keep it all cool. Remarkably the frame, which was never exactly a GPz strong point, is original Kawasaki, though not exactly as Kawasaki designed it.

“The upper part is GPz900 while the lower section is GPz1100,” Harigae tells us. “I combined the two frames into one to give the bike better handling. The 900 is shorter and sportier, however I had to use the 1100’s under-engine frame to give it strength. You can buy custom-built aluminum lower frame sections. I have them on another racebike, but I found my engine was too powerful; it cracked the aluminum. The GPz1100’s steel lower frame is more resistant.”

Jon Urry

The custom-built aluminum swingarm is worked by an Öhlins TTX36 shock.

Jon Urry

Running gear is open under Taste of Tsukuba rules, and the GPz has a fully adjustable Öhlins Road & Track fork with Nissin forged-aluminum four-piston radial calipers. Wheels are forged-magnesium JB-Power Magtan.

To this combination frame Harigae fitted a custom-built aluminum swingarm, full Öhlins suspension (including a steering damper), forged magnesium lightweight wheels, and some ferocious Nissin radial calipers. As this particular GPz was unlikely to be used for touring he also built a smaller aluminum petrol tank that locates under the dummy one-piece fairing/tank.

Having spent more than four years developing the bike, has Harigae’s creation succeeded on track? “I think we win around 80 percent of the races,” he declares with more than a little pride, before adding, “although I could have probably bought a house in this area for the same amount I have spent on the bike…”

As well as beating the Desmo, at some tracks in Japan this mid-1990s commuter is less than half a second off the pace of a Japanese superbike. However that could be to do with the “enthusiastic” riding style of his number-one rider, the wonderfully nicknamed Human Torpedo.

As I prepare to leave I spot the logo on the bike’s tank and ask Harigae what that signifies. “The ‘neko’ in ‘Nekozane’ means ‘cat,’ which is why we have the cat logo,” he answers. I ask what the Japanese symbols say. He smiles before answering, “That reads, ‘I’m going to kill you.’ It’s a racing thing.”

Jon Urry

Another GPz1100 built by Nobuaki Harigae.

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