crossplane_crankshaft.jpgAcknowledging that, deep down, every motorcycle fan has the intellect of a seven-year-old, Yamaha has come up with a nifty song to help us understand how the 2009 Yamaha R1's crossplane crankshaft engine works. The secret’s in the firing order. Whereas a traditional inline-four goes: one, two, three, four, combusting on each number, the crossplane crankshaft engine goes: one, two, three, one, two, one, one, two, combusting on the ones. Try singing it with a drum set keeping a beat, or just watch this video.
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Basically that means two cylinders fire with the normal degree of
separation before two cylinders fire one after the other, creating a
long bang. It’s this long bang that gives the engine its unique
character, sending large pulse of torque to the rear wheel, then giving
the tire plenty of time to regain traction before the next one comes
around.



This differs from a big bang engine in that it doesn’t fire two-by-two.
That arrangement creates huge levels of vibration (also a problem on a
long bang engine, they’ve fixed it with a counter-rotating balancer)
that would impact engine longevity in a production application.



This arrangement is given the confusing "crossplane crankshaft" moniker
due to the lobes for the outer cylinders being pointed in the same direction,
then the inner cylinder lobes being horizontally opposed, 90 degrees of rotation from the outers.



This was all a lot simpler than we thought it was, but we feel
strangely satisfied, in an elementary school kind of way, for having
learned something new thanks to mnemonics.

Thanks for the tip, Sean.

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