All four Yamaha MotoGP riders took part in the global unveiling of the all-new Yamaha R1 in a glittering show in Las Vegas, Nevada on Monday.

Fiat Yamaha riders Valentino Rossi and Jorge Lorenzo, plus Tech 3 Yamaha team-mates Colin Edwards and James Toseland were surprise guests at the unveiling, which took place in front of 3000 Yamaha US dealers at the famous Mirage Hotel.

Significantly, the new R1 features an uneven firing 'big bang' type engine design, similar to that used in Yamaha's YZR-M1 MotoGP machine since 2004.

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"This is a great bike, it's very like my M1 and it's exciting to see so many MotoGP qualities now appearing on a bike for the road," said Rossi, currently on target to win his first MotoGP title since 2005 and his sixth in total. "I think everyone who loves the R1 and Yamaha will be very excited about this new version, it's fantastic!"

Total engine torque is a combination of combustion torque, produced when a cylinder is fired, and inertia torque, produced by the rotation of the crankshaft. Of the two, only combustion torque is controlled directly by the rider, via the throttle.

Uneven firing 'big bang' engines improve rider feel by reducing the effects of inertia torque, but they are also more complex and reduce ultimate engine performance slightly compared with a conventional design.

During winter MotoGP testing, Masao Furusawa, Yamaha's general manager of Engineering Operations, told Crash.net that the company will 'never' use an even-firing engine in MotoGP again.

'Big bang' engines have not been used in World Superbike due to a rule which states that "the sequence in which the cylinders are fired (i.e. 1-2-4-3) must remain as originally designed on the homologated model".

But since the 2009 R1 features uneven 'big bang' type technology as standard, Yamaha will be able to use it in WSBK next season.