In the last decade or so, two classic automobiles have come to define a deep desire within the enthusiast community. Each represents a time when vehicles were entirely analogue, designers were Renaissance men, and their machines were styled in steel. Both are German, each uses an air-cooled boxer engine, and Robert Sabel is an expert in both. They are the Porsche 911 and the BMW R series, and the boss behind the Roughchild brand has made the boxers his life’s work. So, as luck would have it, when a man with an Irish Green Porsche 911 Turbo wanted a matching BMW R for some canyon carving, he knew there was only one place to go. The resulting 1974 BMW R90 is as good as it gets and would be right at home, taking pride of place, on any concourse.
The owner of this beautiful BMW lives in Malibu, California, and seeing his green Porsche brought back some fond memories for Robert. “The colour resonated with me as I previously built a 1966 Porsche 912 from a basket case and sold it when my daughter was born. Back in the gold rush of the Porsche era, around 2012, I was exporting ’60s Porsches to Europe and Asia. During that time, I bought and sold a lot of cars, and the 912 was unsellable. It just needed too much work. Years later, I finally bit the bullet and set about building that car. Then I kept it for 8 years.” The ’74 BMW arrived in a similar way, part of a haul of bikes from Texas, and it too was in poor shape.
But even though it was rough and completely disassembled, it was a numbers-matching bike, and when you’re talking classics, that’s always a good place to start. The drivetrain was the first part of the motorcycle to go under the knife. The engine received a full rebuild, with the case blasted with glass media and then cleaned in an ultrasonic tank. Nikasil cylinders were employed and house a set of new 1000cc pistons, while the cylinder heads were totally rebuilt, given a new valve train, and treated to a twin-plug conversion. The gearbox has also been fully rebuilt, with a longer 5th gear for reduced RPM at cruising speeds.
“As part of the twin-spark ignition, we had to house the additional coil. We did this by installing it under the front timing cover and drilling the sides in the style of the /2 era bikes. To do this, we needed to free the space previously occupied by the diode board. We upgraded the charging system, which now comprises a rectifier mounted on the frame under the gas tank,” Robert explains. The fuelling is handled by a set of SmartCarbs, which not only look the business but provide some of the best mixture control money can buy. Completing the engine package is a stunning exhaust system, finishing with a pair of reverse-cone stainless steel mufflers.
Of course, you can’t build a brilliant retro-tech bike without upgrading the suspension and braking package, and the front end has all of the best bits. Utilising a custom set of triple clamps allows for the fitment of a set of USD Ohlins forks, and finished in black, they strike the perfect visual tone. The machined lowers allow for the fitment of radial-mounted calipers, and it doesn’t get much better than a pair of Brembo monoblocks clamping a large set of discs. The rear end features a set of Ohlins fully adjustable shocks, with blacked-out progressive rate springs.
The hubs are the factory BMW items, which really help to balance out the modern tech employed on this classic machine. They’ve been re-laced to a set of lightweight rims and wrapped in Avon tyres. “We went with 17s in this instance in case we needed to lower the bike even further for the owner. In that case, it would be just a matter of changing tyres, and we can get even lower. I’m really enjoying the look of the big tyres though, and the ride is super plush with this setup,” Robert tells us. Steering duties fall to a set of custom-made handlebars, and the internal throttle mechanism provides a sleek finish.
“We developed a new subframe this year, and this is the second bike to get it. It’s a development of our previous version that not only lowers the riding position but also allows for a lot more padding in the seat, which in this instance comprises a gel insert within the foam. It is really very comfortable. The Alcantara is the same as you’d find in a Porsche GT3 and does a great job of providing extra grip.” The black of the seat flows flawlessly into the knee pad rubbers and black pinstripe work on the tank, but it is that green which truly brings the entire bike to life. And the custom badging, with the BMW logo, leaves you in no doubt as to who built this beauty.
“A /5 headlight bucket was gutted and reworked to house an m-unit that forms the heart of the electronics on the bike. Again finished in Irish Green, the factory buckets were always finished in black by Bosch, the factory’s parts supplier. That’s significant in my mind, as the black on the factory bikes never really matched any other black on the bike,” Robert details. There is more of the green and black mix on the custom front fender and spotlights on the crash bars sport the same colour combination. It’s simply a beautiful BMW and paired up with his Porsche, the owner has one hell of a decision to make when it comes to picking which he’ll take out for some canyon carving; for us, it’s the Roughchild R, all day.
[ Roughchild ]