The modern dirt bike is an incredible thing, blisteringly fast, effortlessly reliable and able to handle and stop like on rails, no matter how terrible the terrain. And yet, never have vintage motocross, dual sports and scramblers been as popular as they are now. Some of that is nostalgia, no doubt, but there is also the fact that every manufacturer’s machine was uniquely different and no two ever looked the same; something that cannot be said for the current crop. So, it should come as no surprise that shops that do one hell of an MX-inspired scrambler based on these bikes are doing a roaring trade. And few do it better than Australia’s Purpose Built Moto and their latest is this Yamaha XT500, with bold looks, big power and attitude to burn.

2023 was another massive year for the Gold Coast’s PBM, and one of their best builds was a furious Fat Bob. “As we were finishing up Phil’s 2022 Harley Davidson FatBob he came in for a shop visit and a DT400 Scrambler happened to be on the bench being finished up. It instantly caught his eye and he became very curious about this build that seemed to be the exact opposite of his plush HD Fatbob build,” Tom Gilroy explains. And it seems Phil got bitten by the bug, as before Tom knew it, a couple of donors were on their way to the shop. “So we’d started two more projects for the same client before we had even finished the first.”

But as is often the case with these sorts of machines, the donor XT for this project had sat in a dusty old farm shed for a good period and there really is only one way to know its true condition. That means pulling the whole thing to pieces, and if the engine was coming apart, the PBM team was going to treat it to a serious rebuild. It’s rare to see an XT engine that isn’t all black, or at best had some file finishing. But a brilliant touch for this build was to totally blast it and then treat various elements of the engine to either a chrome or polished look. “ The power plant has been upgraded with oversize valves, megacycles street cam, port and polish work, high compression big bore kit, performance coil and a high-performance clutch.”

On the outside, the bolt-ons take advantage of the internal modifications and pouring fuel on the fire is a flat slide Mikuni carb. As always for PBM, the exhaust is a one-off fabrication and the stunning stainless steel header has an FMF PowerBomb integrated into the design, before running rearwards and finishing in an iconic Australian muffler from the revamped Staintune. Over to the frame, and the bike gets a big upgrade to get things rolling, with improvements in handling and braking almost immeasurable in the past forty-plus years. The rims are lightweight Excel items, a 19-inch for the front and 17-inch for the rear, with a dual sport style Pirelli tyre chosen to match the type of riding Phil has in mind.

That front end is clearly not stock either, taken from a modern KTM 250SX, adapted by PBM to fit the XT, and lowered and rebuilt internally by Charlie Costanzo. You get the benefit too of the latest KTM braking package and then to tame the terrain, YSS Australia supplied a set of their 40mm over rear shocks. Now the guys had one hell of a roller on their hands, it was time to get it looking just right and there is a distinct philosophy behind the approach. “The whole idea of these VMX-inspired scramblers is always to create our version of what that motorcycle should be,” Tom explains. And it’s all about combining the old and the new, with the factory side covers retained for their nice styling, but the right side given a heatproof treatment to handle the new exhaust placement.

“We’ve fitted an aftermarket XT500 tank and modified it to sit a little lower over the engine to create a more streamlined top line. The new tank came into the picture as the one supplied with the bike was a wreck and not really worth repairing.” The engine-hugging look is a brilliant touch, but it’s the front end which really transforms the bike’s appearance. The fender is high mounted as you would expect, but crafted brilliantly from aluminium it has the picture-perfect shape to get the job done, without being so big as to be unsightly. And teamed up with that beautifully beaten-out headlight shroud, again hand-made from aluminium, you get a look like no other.

“On the rear, we’ve again hand-made an MX style fender from aluminium. The design includes rubber mounts, bracing the tail tidy and integrated lighting mounts for the 3 in 1 hollow tip tail lights. The rear set up on this bike is a real favourite of mine,” Tom smiles. And he’s got the lighting at the front spot on too, with that shroud hosting a 4.5” flashpoint headlight, as well as button lights to serve as DRL/Low beam and a set of Omni lights as indicators, all of which creates a real off-road vibe. The rest of the electrics package sees a set of 3-button switches to control all the goodies, all run through PBM’s own Black Box control module. More PBM parts get the call up in the way of their scrambler mirrors, which mount to a set of Renthal fat bars.

To handle off-road duties, the controls include a set of beefy pegs, a nicely sealed battery box, an inner fender to catch the last of the dirt and a small bash plate to protect the thumping single engine. “ Using a number of polished aluminium pieces, we’ve designed the paint scheme around the iconic white, red and black Yamaha colourway relying on Justin from Popbang Classics to lay the colour down and bring the idea to life.” And to complete the look, the seat was handled by Jamo at Timeless Autotrim for the perfect upholstery in a gripper black leather with paint matching red detail. The big single is now ready to kick in the guts and light up back lanes and tiny tracks, but even standing still, this XT500 is a vintage vixen to make any fan purr.

[ Purpose Built Moto | Images by Full Creative Imaging ]