BACK-TOFRONT BMW

Motorcycle News (UK) - - This Week -

BMW’S G-se­ries mo­tor is a re­verse cylin­der de­sign, which means its ex­haust ex­its from the rear of the en­gine in­stead of the front and the cylin­der is tilted back­wards. But why have BMW done this? On a con­ven­tional mo­tor the cylin­der leans slightly for­ward but by tilt­ing it back­wards on the G310s BMW have cre­ated ex­tra space un­der the cylin­der, al­low­ing them to use an in­line gear­box and still have a short en­gine. Sports­bikes achieve the same goal by us­ing a ver­ti­cally stacked gear­box, but this so­lu­tion raises the weight of the gear­box within the bike’s chas­sis. By tilt­ing the cylin­der, BMW have kept the weight low in the frame and kept the en­gine short and a short en­gine takes up less space in a chas­sis, so you can fit a longer swingarm for bet­ter drive. BMW aren’t the first to ro­tate the cylin­der head through 180 de­grees – Yamaha and Can­non­dale have done it too but BMW have done it for more rea­sons than en­gine length. By mak­ing the ex­haust exit at the rear of the en­gine, it is a very short dis­tance to the cat­alytic con­verter, that means the ex­haust gases heat the cat faster and it gets rid of emis­sions with greater ef­fi­ciency. As a re­sult BMW can use less ex­pen­sive cat­alytic ma­te­rial, keep­ing the costs of a bike down – an es­sen­tial fac­tor on a price­sen­si­tive model.

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