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‘74 BMW R90S – Boxer Metal

Posted on April 7, 2016 by Andrew in Café Racer, Racer. 16 comments

Hot on the heals of their 1 Show winning, twin turbo’d, controversy stirrin’ R100, Boxer Metal have graced our eyeballs yet again with this, their latest creation. Riding high on the current wave of love for all things boxer, the shop seems like they can do no wrong. And, as if to rub that fact in our appreciative little biker faces, they’ve gone and topped the untoppable. Sure, those two turbos would be a real damn hoot for a while… but what happens when you start to miss carving up the corners? This happens. It’s 70s. It’s orange. It’s fared to within an inch of its 42-year-old life. It’s Boxer Metal’s beautiful R90S.

Boxer Metal are partners Chris and Rebecca, who met while working in and around the American BMW motorrad seen. “Between my wife and myself, we have over 30 years of building, racing, riding and loving BMW motorcycles and sidecars,” says Chris. The Boxer Metal shop is located in Northern California, at the foothills of the Sierra mountains. It’s no coincidence that the area offers some of the best riding in the entire country. “We specialize in custom BMW motorcycles, restoration, and sidecars. We pretty much do everything. Including 3D printing.” Such has been their success of late, the shop is now launching its own line of boxer go-fast parts. Need a turbo with bespoke fuel injection system for your airhead? These guys have it covered.


“We found the donor bike locally; it was less than 5 miles from the shop, up a windy river road that we use as a test track. We’re surprised we hadn’t seen it sooner!” Once it was back at base, Chris and Bec took stock; it was a stock 1974 BMW R90S that had the wrong bodywork and seat, and lots of rather unfortunate aftermarket parts. Bad for a restoration, but perfect for a custom build. “In the end we used the frame, motor, transmission, rear drive and wheel hubs. Everything else was either newly purchased, built, or replaced with other 70s BMW parts.”


The build was inspired by the likes of Helmut Dähne, the famous 70’s BMW racer and Chris’ idol, Reg Pridmore, who won the inaugural A.M.A. ‘76 Superbike Championship on a BMW R90S. In the face of a strong Japanese bike headwind, Reg was probably responsible for more BMW sales in the US than any other man of the time. So Chris, having built his fair share of vintage BMW road race bikes, knew pretty much exactly what it would take to build a bike that would be something more than a shallow homage. What he was after was authenticity.


“Essentially, what we were going for was a street-legal version of a 1970’s BMW road race bike. We started by cutting up a stock BMW frame to make it lighter and stronger. This wasn’t as simple as it might seem; making a frame lighter while also ensuring strength and straightness was a real challenge.” Then came the donk. The stock and somewhat tired original engine was rebuilt from the ground up, and its capacity was taken from 900cc’s to 1000, which also managed to lift the horses from a lukewarm 63 to a much healthier 78. The power boost was no doubt helped along by the addition of a set of tuned Boxer Metal headers that travel high down the length of the bike and spill their sweet monoxide magic out of its petite, speedy tail.

Next came a set of 38mm Dellorto carbs which, once perfectly tuned, completed the bike’s go faster make-over. Sensibly, they now turned their attention to the bike’s stop faster parts and bolted on some dinner plate brakes (that’s 320mm rotors, in layman’s terms) and pinched them with some super stoppy twin piston Brembo calipers.


The robot liked his new yellow helmet

Naturally, the last step was to paint it like the 70s. Orange it is! The end result is something that Reg Pridmore would have ridden with pride. This is no doubt helped by Chris including his race numbers on the bike’s derrière. And there you have it; a road-ready race bike that should turn heads with whiplash speed and also cause quite a stir on the Sierra’s faster corners this Californian summer. Were not sure about you, but we are more than a little stoked to see what Bec and Chris come up with next. But guys… please. No more turbos. We’re not sure our delicate little hearts could handle it.


Now THAT’S a spray job

[Photos by Enginethusiast]

  • AMDcb500

    Really nice! but… now that I have seen these engines sit parallel to bottom rails, all I can see is that tilted boxer. Think if the exhaust was parallel to the top rails that might help too. Silly nitpicks as this is really a stunning build.

    • cagivarider

      Well it may look a bit awkward, but all race BMWs need upswept engines
      to provide sufficient ground clearance. Due to the bevel drive the rear of
      engine has to stay in place , so raising the cylinders tilts the engine back-

      Kind regards

      • Hardley T Whipsnade III

        Actually Sven after some extensive research both online and my personal library that included the bikes Mr Pridmore rode the overwhelming majority of BMW’s race bikes did not have upswept motors and the few that did had a very minor almost undetectable upsweep whereas this builds upsweep is exaggerated to say the least . Add to that this builds somewhat awkward overall appearance including a fairing that simply does not fit the bike , the build nor the intention [ its neither authentic or classic BMW ]

        I must conclude that in my opinion such as it is : that whereas Boxer Metal’s previous Twin Turbo build featured here was a brutal , masterful not to mention an engineering masterpiece as well as a serious functional beast ; This bike is doing nothing for me at all . Certainly the craftsmanship is superb . But the aesthetics ? Not so much .

        • cagivarider

          ” … this builds upsweep is exaggerated to say the least.”

          Well at least the lower engine mounts are exactly the way
          as in any race prepped Beemer, rear mount at the center
          of the tube, front mount on top (stock: both below). Maybe
          that’s more than necessary, but a well proven solution.
          Stock doesn’t work on track.

          Kind regards

        • Pridmore Bemer

        • Level stance

          • cagivarider

            In the second pic (RAD-BMW) you can see the modified
            engine mounts, same as the Boxer Metal BMW has. As
            mentioned, stock is both below frame tube.

            Kind regards

  • Dave Coetzee

    I must agree with AMD.That first pic doesn’t do this fine build any justice, I.e. rear shock angle and backward stance, that some may even prefer.

  • blackbird

    Yo! Hey man, thanks for fresh perspectives and angles with this build. Big fan of your bikes and thank you for keeping us airheads moving on the road with your shop. If you ever get out of NorCal, you should come ride Montana. I bet we could give your twisty NorCal roads a run for thier money, the camping is ridiculously good. Thank for sharing your build.

    • Rebecca Canterbury

      Thank you!

  • Great idea for a heated seat ! It’s freezing outside today

  • Nice workmanship but the stance (Lines) are about as odd as I’ve ever seen. Looks like dropping the fairing 6-8″ might help a lot.

    • cagivarider

      “Has the fork length been extended?”

      Probably not, older Beemers have some 200mm (=8″)
      fork travel. BMW mentioned this in their ads, claiming
      “short travel may look sportive, long travel makes you fast!”

      Kind regards

      • lemieuxmc

        Dude, how old are you?

        It’s easy enough to build an exact replica of a ’70’s race bike (if you have some $)… Rob North is still working, and you can probably meet Reg Pridmore in person next month at The Quail and ask him stuff yourself.

        • cagivarider


  • Fido Zombie

    The look is all wrong – too jacked up.
    It reminds me of folding bicycle with small wheels.