There are at least eleven different models released by Honda known as the CB400, but the one that built the reputation is the unmistakable ’70s F, with its iconic 4 into 1 exhaust and deliberate cafe racer styling. It was meant to be a ‘slap together’ while Honda’s engineers focused on cars like the Civic, but the small team on the two-wheeled project knocked it out of the park and helped to set a standard for fun and reliable middleweight motorcycling. It was with this love and appreciation for the CB400F that a client approached Purpose Built Moto for a full build of their own. They were thinking of the murdered-out look, but the builder was hesitant and so together they came up with this beautiful black beast with a striking purple heart – and she’s still more than capable of manslaughter.

“When Will, our client from Victoria got in touch about his Honda 400 four and explained the sort of thing he was after it sparked a bit of intrigue for me. He wanted us to build a pretty dark-styled café racer, and didn’t really want us to stick with a classic style set,” PBM’s Tom Gilroy explains. But as Tom discussed with us, the all-black appearance can have a cheap look and often seems like someone has just hit the bike with a rattle can of matte black rather than actually build the thing properly. So, after some consideration and fruitful discussions, a plan was mapped out to give the Honda a full custom build and give it a “dark and moody” vibe.

The subframe had previously been modified, but not very well, and it was while the PBM team was undoing this damage that Tom had an idea. With the thumbs up from Will, modifications commenced on a full mono-shock conversion and the fabrication work is brilliant. The braced swingarm uses a triangulated mount fabricated from chromoly tube, with the upper end of the shock attached where the backbone meets the centre post for maximum strength. Some photos were taken and the maths was done, and the good folks at YSS Australia put together the perfect shock for the job.

As all of this fab work was being done, the wheels were completely rebuilt with new bearings and powder-coated hubs, and some 18” black Excel rims wrapped in Heidenau tires. To match the rear, the front suspension needed a rebuild too, so new fork tubes, springs and preload adjusters get the job done. “Time for some styling. I had a CB400 café racer tail from Justin at Popbang from a previous project that we decided to use, Dylan set about making mounts for the new tail, electrics tray, and seat. The battery box was fabricated to sit under the swing arm hidden away neatly. Once these parts were laid up the scene was set for the rest of the detailing.”

To get the front end looking as good as the fabricated rear, a PBM universal fender kit, with a nicely shaped aluminium fender, looks trick and is something you can do yourself at home on just about any bike with the kit. Now for the paint, “ from previous conversations with Will, I knew he wanted the colour palette to be dark, so you can imagine his surprise when I suggested purple,” Tom smiles. But not just any purple, the hue is from the legendary Nissan GTR and before it was expertly laid down by Nathan from Livin Loco, a little extra black was mixed in to darken the mood.

The look is a sensation and goes to show the benefit of exploring colour options from the JDM world or other automotive scenes. Such a stunning paint job needed the upholstery to match, and Timeless Autotrim does beautiful work, with a black leather seat that has just enough custom detail to really set things off.

The look is kept clean with the tightly tucked 5.75” Flashpoint LED headlight and the rest of the accessories are of a similarly high standard. The low bend bars sport Accosatto levers, PBM’s own 3 button switches and mirrors, a Domino throttle and some Biltwell grips. “Up front, we also have a single 60mm Daytona gauge, with all the electrics operated by our Black Box control module.”

Here many would throw on an exhaust and call it done, but with PBM now having Purpose Built Performance, their own in-house engine building and tuning operation, there was no chance the Honda Four was being left untouched. After carrying out a bunch of testing, the motor was stripped and a 466cc big bore kit fitted to help up the power output. The head has been ported and polished before new valves with Kibblewhite valve springs were fitted. A performance clutch helps to transfer the extra power to the Honda first 6-speed box and it’s all brought to life by a modern Dynatek digital ignition and coils.

The iconic 4-1 exhaust was in terrible condition, but Tom and Will really wanted to retain the look, so hours of meticulous fabrication was poured into rebuilding the original pipes back to their best. They finish with a PBM torpedo muffler and have been ceramic coated for an ultra neat finish, with the rest of the engine coated in a gloss black.

From here Tom would normally select a set of Mikuni RS carbs, but Will wanted to retain the originals and they look spot on having been completely stripped and rebuilt and fitted with a set of DNA pod filters. Out on the road for a shakedown and “tight corners, some nice inclines and banked turns makes for a great experience,” Tom grins. And now it’s Will’s turn to smile, having partnered with the right shop, he’s got an icon that looks and performs like very few others of its ilk.

[ Purpose Built Moto | Photography by Ninefivers ]