You either love the idea of trying to make a twin-cylinder air-cooled engine that’s based on an old 1923 knocker go like the clappers, or you don’t. If you don’t, life is simple: you buy a Fireblade or an R1 and go zooming about. If you do you kiss goodbye to normality and sign up to the fringes of mainstream motorcycling, driven by an irrational need to ride a bike that makes its speed the hard way. In the case of the BMW boxer that speed must come from this 90-year-old design, which, compared to the near-weightless internals of modern superbike engine, reciprocates with the urgency of Stephenson’s Rocket. Being a BMW that engine must also be mounted in a rolling chassis that is fundamentally designed for touring. So when in 2007 BMW wheeled out its most daring boxer ever to compete against the 190bhp Japanese superbikes in the World Endurance Championship, it was almost too much for followers of air-cooled BMWs. The HP2 elevated the old twins to a new level of willful