It is a strange old world we live in, the demise of the British motorcycle industry in the ’70s was largely down to the nation’s manufacturers not having evolved past the humble parallel-twin engine. And yet fast forward to 2023 and nearly every manufacturer not only makes a twin but sells a boatload of them too. Over the decades, one of the truly great examples of the platform has always been the Yamaha XS650, raced by King Kenny Roberts, sporting timeless good looks and an engine which has always been a customisers delight. For engineer and back shed builder, Matt MacVittie, the model would serve as the perfect donor for his 8th full custom build, and rolling out of the MacVittie Motorcycles garage, this 1974 Yamaha XS650 is such a star, he’s called it ‘Cosmic’.

Matt’s been at the custom building game for a few years now, and the combination of an enthusiastic love for bikes and an engineering background has resulted in some of the best backyard builds you will ever see. Focussing largely on classic Japanese bikes, his CB750 build was so bang on that one of the big Japanese magazines gave him a full feature; and they have notoriously high standards. His style is easy to spot and even easier to define, “I like to make fun, reliable, eye-catching mobile works of art,” he tells us. And picking a parallel twin means he’s also operating with an engine configuration that is, for good reason, the flavour of the month.

Sadly, the donor was not so tasty, “This project came in a bunch of boxes and the subframe was mangled. It then became clear I was going to have to do some sort of monoshock build (not an easy task with the XS650 frame),” Matt explains. This difficulty can be seen in the endless way builders of monoshock XS builds have gone about the process, unlike the CX500 for example, where most conversions look almost identical. For his part, Matt decided to engineer an all-new swingarm to suit, utilising a quality HyperPro Racing shock. And it’s a work of art, with the tubular design tying in nicely to the rest of the frame and featuring supports in all of the right places.

The front end really captures the old-school British feel, but it’s taken a lot of work to achieve both the look and yet also enhance the performance of the motorcycle at the same time. It all starts with a hub from another Japanese maker, taken from a ’72 Suzuki GT750 4LS which has been polished to perfection and laced up to a lightweight Excel rim. But the changes to the hub don’t stop there, to get the look of an old drum and still have a decent feel at the lever, Matt has made the conversion to a hydraulic master cylinder for actuation, and given the clutch the same treatment.

The lower fork legs and upper triple tree are all beautifully polished up and Matt has added a set of external dampening springs to give the ride a smoother feel. A set of old Honda forks covers added more vintage appeal and also gave Matt the perfect place to mount a set of blinkers, while also being able to use the covers to hide the wiring. Fitting neatly at the top of those covers is a set of clip-on bars, which is the first part in the process of creating a more sporty riding position. Finally, the front end is finished out with a stunning Harley-Davidson headlight that was found at a swap meet, with a super clean bracket used to mount it.

Now having crafted such a quality roller, Matt could move on to getting the visual elements bang on, and it’s not often we get so excited about a subframe. The metal work is simply stunning, flowing beautifully off the backbone, the tubular item floats over the rear wheel, with a nice upkick and wonderfully shaped cowl. This neatly fills the section behind the seat, with the rider’s saddle expertly stitched together in a mix of traditional and diamond stitching. The fuel tank is taken from the larger XS750 and yet helps to give a new take on the already stunning XS650 lines, while a rolled fender and custom struts complete the tins.

The parallel-twin engine in the XS650 has always been a favourite, and long before Yamaha was fitting crossplane cranks to their parallel twins, racers had been changing their phasing. Matt’s fitted his with a 277-degree crank along with the associated cam modifications, and the sound alone is worth the price of admission. To ensure the timing matches, a VAPE electronic ignition system that is designed for the 277-degree conversion is wired up and the whole charging system has been updated to 21st century components. The carbs have been given pod filters and a tune and the engine is topped off with those big header pipes which flow rearwards to twin reverse cone mufflers. 

The finishing work on this build is all exceptional, and the rearsets on custom mounts complete the more sporty riding position. The underside of the seat pan is as neat as can be, and taking it one step further, Matt has moulded in the taillights and further cleaned up the back end by crafting an axle-mounted number plate holder. The controls share the minimalist approach, with modern mini button switch blocks, bar end mirrors and a single gauge. Finally, the choice of colour scheme is inspired, Matt lets the quality of his work shine through with the understated hue and simple graphics, and it’s another ’70s stunner to roll out of the MacVittie Motorcycle’s man cave.

[ MacVittie Motorcycles ]