Shiro Nakajima of Japana’s 46 Works has the kind of fabrication skills most could only dream of possessing. As a trained engineer his work is both intricately precise and highly functional and his keen eye for design means that everything he produces looks every bit as good as it performs.
Shiro’s latest work of art, a KTM 690 Duke cafe racer, was his entry into the 2023 Mooneyes Yokohama Show. It also happens to be his personal ride and a project he’s been hoping to complete since the early nineties. After seeing the bike pop up online after the show we reached out to Shiro who has shared the story of the project along with some exclusive photos of his KTM cafe racer.
“In the late 1990s, the first motorcycle I acquired was a Yamaha SR400,” Shiro recalls. “It was the heyday of racer replicas, and I was riding around on that SR400, fully banked on the mountain passes. To me, a big single is not a nostalgic object, but a sport bike. At the time, it was popular in Japan for some enthusiasts to race single bikes, and the races were so exciting that some failed to qualify.”
Those days of getting his knee down on the SR left a lasting impression on Shiro. Despite moving on to bigger capacity Euro bikes, like those he built while operating under the title of Ritmo Sereno, that zesty little single continued to appeal decades after owning it.
As time passed Shiro’s skills as a builder and rider increased tenfold so when the time finally came to build himself a custom single, he wasn’t about to cut any corners. This time around though it wasn’t Yamaha’s evergreen thumper that he’d be working with, instead he opted for KTM’s mid-range supermoto the 690 Duke.
“Over the next 30 years since owning my SR several big single sports bikes were launched, but many were produced in small quantities or were expensive,” he says. “About 15 years ago, I rode a KTM DUKE for a test ride for a magazine and was very impressed with the LC4 engine, which felt like a tuned single racer. So I decided to build a single sport bike with this engine.”
“When my 46 Works, ‘Building the Ideal Big Single Sport’ project began (watch it unfold here on Youtube), I tested a 2017 KTM 690 Duke which I had purchased in fully stock condition,” says Shiro. “I tested it on city streets and mountain passes, and I also tested it at the race track at full throttle. As a result, I preferred the more flexible handling using the rich suspension stroke, so I decided to create a road sport without changing the body posture, ride height, or suspension stroke.”
Although Shiro was impressed with the Duke’s handling characteristics and riding position, its look wasn’t his cup of tea. So he set about restyling the angular Duke to turn it into a compact, classically inspired ride.
“I do not see anything benefit from lowering the bike, except for the footing aspect. The lower you make it, the more boring the handling becomes,” Shiro explains. “So on every bike I have ever built, I have not done any custom lowering. Lowering is one of the easiest ways to make a bike look cool, but I am always thinking about other ways to achieve that.”
Luckily Shiro’s got the skillset to do exactly that.
As with most of Shiro’s creations, the KTM features a long list of handmade components designed and built by the man himself. The fuel tank and tail unit are 2 examples and they sit flat on the trellis frame to create a beautifully balanced bone line. To make this possible Shiro fabricated a truss subframe that houses a special aluminum enclosure.
“The aluminum box under the seat is an air box that uses the factory air cleaner element and also serves as a mount for electrical components and the battery,” he explains. “Although not visible in these photos, the air intake is located behind the rear suspension and is funnel-shaped.”
The spoked wheels, which are wearing purposeful Pirelli Diablo Supercorsa rubber, have been retrofitted from another model in KTM’s lineup. Both fenders are custom-made from aluminum and there’s even a svelte chain guard that Shiro once again built from scratch. In keeping with the sportier demeanor of this KTM, Shiro added a set of bespoke rear set footpegs that he turned on his in-house mill.
“This time I made the top bridge (triple tree) with a general-purpose milling machine. That is because the clip-on handles are mounted on the top bridge without lowering the ride height, for both styling and an easy riding position. This was also done to allow me to mount the stock meter compactly.”
Up front the 690 Duke is also wearing a one-off mini fairing that pulls the headlight in tight for more compact proportions. The titanium muffler is a one-off too and there’s a raft of bespoke brackets and hardware to hold everything in place. And rounding out the custom-made components is a very special set of mirrors.
“When a custom bike is built and mirrors are installed at the end, the bike often looks instantly uncool,” says Shiro. “To avoid this, until now I have often made one-off mirrors. As a result, I have had many requests to produce a series of mirrors. So for this project, the mirrors were jointly developed with TANAX, one of Japan’s leading mirror manufacturers. These will be commercially available in the spring of next year and the one you see here is the mass production prototype we developed.”
To complete this project Shiro’s also pulled together a few aftermarket additions from some of his favorite suppliers. The top-mounted clip-on bars come courtesy of Japan’s Battle Factory while the tiny turn signals are KIJIMA items. The carbon fiber belly pan is a universal part from Future’s Craft and the new seat was built by his friends at Razzle Dazzle.
Finally, Shiro tasked his go to paintshop, Drops Design Works, with adding a splash of color to his Duke. Shiro admits the decision to go with a candy green scheme has raised a few eyebrows, but the color was actually inspired by early model Dukes. Along with a hat tip to those bikes, Shiro went with this color to buck current manufacturer trends of using earthy hues on their latest models. “This is the antithesis of those colors,” he says. “Doing something unusual can cause rejection, but I don’t mind and move on.”
No matter what anyone else says, Shiro can rest assured we wholeheartedly approve.
