Custom Triumph Bonneville Is a Visual Nod to One of Steve McQueen’s Fabled Desert Sleds

Shiro Nakajima has long been building custom marvels under the alias 46Works, operating right near the Yatsugatake mountain range in the quaint Japanese countryside. His talents extend far beyond bike-building, though, and he’ll often indulge in things like vintage car restorations and crafting furniture. Mind you, 46Works wasn’t even the first motorcycle customization outfit that Nakajima-san had established.
Custom Triumph Bonneville 9 photos
Photo: 46Works
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He is the founder and previous owner of Ritmo Sereno, a firm known for its spectacular restomods well beyond Japan’s borders. Things haven’t gotten any less impressive since Shiro moved on to his second venture, but the machines he puts together are now fully-fledged customs. The specimen we’re about to look at is the latest entry in his project archive, and it broke cover on 46Works’ Instagram page in January of this year.

It started out as a Triumph Bonneville T140 from the model-year 1976, yet our protagonist turned it into something far more exciting. Master Nakajima looked to vintage desert sleds for visual inspiration, eventually deciding to base his design on one of Steve McQueen’s best-known motorcycles. We are, of course, referring to the King of Cool’s famed #955 Triumph TR6 desert racer, which is surely among the most iconic bikes of its kind.

The build was commissioned by a client who sought desert sled styling mixed with tarmac-friendly running gear. He intends to take part in a Japanese racing series called Legend of Classic, and this rad T140 is his weapon of choice for the competition. That’s right; Shiro didn’t just create a visual treat with McQueen charm, but a genuine race bike made to go fast around the track!

Now, he wasn’t exactly provided with a complete motorcycle to use as the project’s basis, because the customer only had the Bonneville’s engine, frame, and swingarm. To get the ball rolling, Nakajima-san tasked the experts over at Gladstone with an all-inclusive powertrain overhaul. The parallel-twin mill was sent to their HQ in Shizuoka, where it gained new cams, high-compression pistons, and Keihin CR carburetors topped with velocity stacks.

Custom Triumph Bonneville
Photo: 46Works
Gladstone also revised the head for good measure, and power is now sent to the rear wheel via a five-speed gearbox and a belt final drive. As for the high-mounted exhaust system, it is a custom titanium unit painstakingly fabricated from scratch by Shiro himself. The pipework comes with a drilled heat shield, as well, so as to prevent things from getting too toasty near the rider’s leg.

Moving on to the chassis, 46Works used billet aluminum triple clamps and a bespoke steering stem to install a fresh set of forks up front. These were sourced from a classic Yamaha but fitted with modern internals prior to installation, while rear-end suspension duties have been assigned to premium aftermarket shocks. You’ll find 18-inch Excel hoops down in the unsprung sector, both laced to repurposed Yamaha wheel hubs.

Avon rubber is present fore and aft, in the form of a Roadrider tire at the front and an AM18 Super Venom at the other end. Plentiful stopping power is an absolute must for any self-respecting race bike, so the T140 gained some serious kit all-round. There are twin AP Racing brake calipers up north, along with a single Brembo module down south and drilled Sunstar rotors on both ends.

Custom Triumph Bonneville
Photo: 46Works
Brembo supplied a pair of high-grade master cylinders, too, and everything got linked together via youthful hoses. On the other hand, the Bonnie’s rearsets and their accompanying linkages are all tailor-made parts manufactured in-house. Cues taken from Steve McQueen’s TR6 are most evident in the bodywork department, with a reproduction Triumph gas tank proudly sitting center-stage.

It’s placed right ahead of a handmade solo seat, which was formed atop an aluminum base and upholstered by Razzle Dazzle. We see custom-built number boards placed on each side of the saddle, as well as a shiny high-mounted fender at the back. Of course, Shiro didn’t need to bother with a license plate bracket or any lighting components since the Triumph was to become a fully-fledged racer.

At twelve o’clock, he added a simple mudguard and a flat number plate with #955 TR6 vibes, but everything about the cockpit has also changed. The instrument cluster is now made up of a standalone lap timer, a digital temperature display from Daytona, and an analog tachometer supplied by Stack. A low-profile handlebar with bare-bones controls rounds out the equipment in that area.

For the finishing touches, the mastermind at 46Works added a Setrab oil cooler complete with Kinokuni fittings, as well as a bespoke oil catch can. The T140 desert sled was then handed over to Drops Design Works for the paint job, which saw items like the fuel tank, rims, and frame finished in a stealthy coat of gloss-black. Other aluminum bodywork components have been left unpainted for contrast, as were the engine covers and titanium exhaust pipes.
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About the author: Silvian Secara
Silvian Secara profile photo

A bit of an artist himself, Silvian sees two- and four-wheeled machines as a form of art, especially restomods and custom rides. Oh, and if you come across a cafe racer article on our website, it’s most likely his doing.
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