The Concept 6 design team was determined not to let the engine blow out to the party-pooping width of the CBX's imposing donk - and it looks like they've done a good job keeping it acceptably narrow. Each cylinder is still slightly oversquare (its bore is slightly larger than its stroke), which will help it spin up and develop horsepower at higher revs, but the stroke is relatively long compared to the ratios used in BMW's inline fours, keeping those cylinder bores as narrow as possible while retaining the ability to rev.
There's very little space in between cylinders, and the alternator and other electrics have been relocated from the side of the engine back behind the crankshaft in the spot above the transmission. The overall result is a motor that BMW claims is four whole inches narrower than the previous thinnest inline six on the market - and only slightly wider than a big inline four.
With a capacity of 1600cc, and all the extra exhaust headers and gear required by an inline six, it's still going to be a very heavy powerplant, but BMW have used a trick from their K-series sportsbikes to neutralize the negative effects that big lump of metal could have on the bike's handling. With the engine tilted forward by 55 degrees, the main bulk of the cylinder bank is kept low, pushing the centre of gravity down and forward, which should help keep the bike flickable and fun in the twisties.
Peak output will reportedly be similar to the K1300 series engines - somewhere around 170 horsepower - but the big six will belt out a massive 130 Nm of torque from just 2000rpm. For reference, the torque monster Suzuki GSX1400 peaks at about 125 Nm at around 4700rpm. The new engine's torque peak is unspecified, but it should rev as high as 9000rpm, making it a hugely flexible powerplant that BMW believes will be "the ideal power unit for a range of different motorcycles." Yummy!