Think big: a beastly CBX1000 from Purpose Built Moto

There is never any moment of calm for Tom Gilroy and the Purpose Built Moto team in Queensland, Australia. Tom started his career repairing old bikes in a shed on the family farm; today he runs a bustling customization business with prodigious manufacturing output, a store full of parts, and he’s even made a movie on the side.

He’s probably seen it all, but he still has the chance to try something new. Like the job he just completed on this somewhat scary CBX1000.

“Every year we get a few projects that really make me step back and take stock of what we’re doing,” says Tom. “This CBX1000 is one of those versions. When Honda released this six-cylinder in 1978, a lot of people spoke: it was not only the fastest production motorcycle ever made, but also a feat of engineering.

With a DOHC, 24-valve cylinder head and solid 100hp at the crank, the CBX1000 is a beast. But it’s also mired in the ’80s. “Our pilot Luke loved his 1981 CBX, but he was starting to get tired,” says Tom. “The bike was due for a refresh, a rebuild and an overhaul.”

Customer Luke is a big guy, and he loves big bikes. He also wanted to bring the CBX out of the 80s and give it a healthy dose of modern flair. After going through the PBM portfolio, Luke and Tom found a few things in common and began to develop a style for the CBX.

“Luke was our ideal client. He came to us with an idea, but he trusted the team to do what we do best – build unique motorcycles to ride, enjoy and watch.

The Honda took the form of a sharp cafe racer, retaining the bold tank of the CBX but adding modern suspension, wheels and performance upgrades. “We wanted to bring out the power the engine already had,” says Tom, “but make it more ‘in your face’ – reducing weight and improving handling. “

After disassembly, the CBX already looked better. “This bike is a Pro-Link model, with an aluminum swingarm and a huge front fairing that weighs as much as a bar fridge,” says Tom. “He dropped 20 kg with the removal of six bolts!

When Tom started measuring the CBX1000, he realized that it wouldn’t be possible to meet the owner’s demand for modern sports bike tires while using the stock swingarm. Before he started cutting he had to run errands and landed on a set of second generation Suzuki Hayabusa forks, along with a 2010 Aprilia RSV4 swingarm and suspension linkage.

The alloy wheels wouldn’t cut it either, so Tom installed a set of JoNich M9 rims, each with 24 spokes. (“The all-black wheelset, with a sparse 9mm spoke layout, gives the Honda an ultra-modern edge.”) The wheels are finished with new Moto-Master rotors all around, as well as a sprocket custom machined aluminum.

The Hayabusa front end was an easy fit with a custom triple clamp. Tom added mid-size ProTaper Contour bars in a “Carmichael” bend, new brackets for the gauges and Flashpoint LED headlight, and a modern, sleek switchgear. Position lights mounted on either side of the powerful CBX1000 engine add a little street fighter touch.

To properly integrate the swingarm, PBM decided to completely rebuild the subframe and seat section. Everything behind the engine cradle was removed, the RSV4 swingarm was pinned in place, and Tom began to mount the lower suspension linkage.

“The idea was to make the upper suspension bracket as transparent as possible. Using the reinforcement on the rear frame, on one side, the shock mount is not visible at all. It also allows for a 180 x 17-inch rear tire, but the real upgrade comes in the form of the bespoke Öhlins TTX rear shock, “compounded at Ride Dynamics for incredible feel on the bike.”

The tail is a little different from the usual hoop design seen on most customs. It houses the battery, starter solenoid, and a set of three mini LED brake lights, flanked by PBM’s 3-in-1 Hollow Tip taillights.

The tank was starting to rust, so it was taken apart and repaired, with a few smoothed seat mounting sections and a pop-up filler cap was welded on. The last piece of construction was on the front fender: “It’s aggressive, but exactly what the front end needed. The paint is simple but extremely effective: a mat gray, with touches of orange details.

The upper end of the engine has been refreshed and a new set of Keihin FCR bolt-on carbs, breathing through DNA filters. The donor bike already had some good performance heads; the only problem was that the six silencers were too long. Thus, six PBM torpedo silencers continued, with custom mounting brackets.

The sound, as you can imagine, is amazing. “It’s like an old Formula 1 engine going up into the rev range,” says Tom, “without being bossy while you’re racing down the road.”

All of these mods have been tuned to perfection at Dynomite Moto, with the CBX now producing 100bhp on the rear wheel rather than the crank. And this CBX has a revised dry weight of just 228kg [502 pounds], down from a 277 kg cruiser [610].

“The first ride on this behemoth was intimidating,” Tom admits. “It’s such a large motorcycle. But once you get on the move, the bike is surprisingly nimble in the corners and holds the road incredibly well. The engine starts to come alive above 4000 rpm, then it knocks over and you won’t know what hit you!

Luke already has a new project in mind for Purpose Built Moto: an even more intimidating Suzuki GSX1400. But until then, check out Tom’s video recap of this CBX1000, which shows exactly what goes into building a bike at this level.

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