Bottpower's XR1R is an American-style flat tracker from Spain built from an American legend (Erik Buell's revolutionary XB12) that was built from another American Legend (Harley-Davidson's Sportster 1200). With more than 150 horsepower and less than 150 kg (331 lb) to shift, it should be a mad little racetrack carver, and it's set to challenge Pike's Peak in 2017.

I've never considered the old Buell XB12 as a bike with much fat to trim. In its day, it was a revolutionary machine – check out Mike Hanlon's write-up of the XB12S from back in 2004, when mass centralization was still a brand new idea in the bike world, and the XB12's 175-kg (386-lb) weight was nigh-on unbelievable for a 1200cc bike with a heavy Harley engine and a full set of road compliance gear. Devastatingly nimble in the corners, it still makes a lot of people's lists as one of the best handling road bikes of all time.

And yet here we are 14 years later, looking at a kit bike custom that throws out that famous Buell fuel tank frame in search of an even lighter and more responsive ride.

Unfortunately named Spanish engineering shop Bottpower has been building a flat tracker kit for XB donor bikes since 2012 in the form of the XR1. There's a strangely bulbous cafe racer version as well, and they've just released this tasty track-only version called the XR1R.

The XR1R looks for all the world like a frameless motorcycle, but in truth its tiny teardrop tank, seat and subframe are held to the motor with a miniscule titanium frame that runs over the top of that big 1200cc Harley motor, and only peeks out at the steering head.

Beyond that, a lot of Buell remains, including the famous twisted pipes, the Zero Torsional Load rim-mounted front brake, the underslung exhaust and rubber belt drive. But the engine's now managed by a Euro IV-compliant ECU that adds traction control and launch control to the menu as well as multiple engine modes and a pit lane speed limiter.

The team has fitted an advanced datalogger that maps throttle, rpm, the speed of both wheels, suspension travel, GPS location, temperatures, brake pressures and more for post-session analysis – that's some pretty serious gear. And because Bottpower is testing the titanium frame against the steel one used in the road-going XR1, they're also logging frame stress at several different points.

When all is said and done, the team is looking for more than 150 horsepower (112 kW) and less than 150 kg (331 lb), which will make the XR1R a furiously fast little beast, an overgrown motard with a hard-pumping American heart.

Exactly why you'd try to build around that Harley Sportster motor in this day and age remains a bit of a mystery to us. It's a good looker and sounds great, but it's heavy and sloppy and low-tech from a performance standpoint. Still, this reinterpretation of one of Erik Buell's most iconic designs looks like a hell of a lot of fun. Check it out from all angles in the gallery.

If things go to plan, we might see the Bottpower XR1R contesting the Pike's Peak Hill Climb in 2017. We wish the team the best of luck!

Product page: Bottpower XR1R

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