Having won the triple crown of Riders', Constructors' and Teams' MotoGP World Championships in 2008, Yamaha needed no fundamental changes to the concept of its YZR-M1 for 2009 - but one word comes up again and again when team members are asked about the new machine; acceleration.

"We're working a lot on the engine and we're trying to find a way to improve the acceleration a bit, and I think that this is the area in which we will be concentrating," said Valentino Rossi of the bike with which he hopes to win a seventh premier-class title.

Just how much significance has been placed on propulsion was further underlined by Daniele Romagnoli, team manager for Rossi's factory colleague Jorge Lorenzo, who revealed that chassis changes are also aimed at allowing the M1 riders to get on the gas earlier.

"In 2008 the bike was successful, so there was no reason to change the concept and the new bike is very similar to the previous one," Romagnoli began. "Changing to Bridgestone tyres, it became clear that the adjustments required were different from the previous set up. So, the new bike can have a wider range of adjustments. This allowed us, during the latest tests, to try different geometries, which improved acceleration after corners because we managed to increase the contact of the front tyre with the ground.

"We've also worked on engine management controls and maps, which enhance acceleration; our riders can open the throttle a few metres earlier. Valentino also worked on the engine and noticed an improvement in acceleration, and he said we are working in the right direction. So, we've just got to wait for the Sepang test [February 5-7] with Jorge to have the whole package. This year the Japanese and Yamaha will surprise again. We're confident the bike will be equally competitive in 2009."

As Romagnoli indicated, Lorenzo is yet to try the 2009 engine - which he believes will be the biggest change relative to last year - but did test the '09 chassis at Jerez in November.

"I had the opportunity to try the 2009 prototype at Jerez. The only thing that wasn't there was the new engine, which I will have for Sepang. The truth is that in terms of handling and in terms of the chassis it seems like the bike has a bit more stability, or let's say that there is less movement on the front end of the bike," said Lorenzo, a race winner in his rookie MotoGP season, when he used Michelin tyres.

"The bike tended to wheelie less on the way out of corners although obviously I have not had chance yet to test the new engine, which they say is going to be the biggest change with respect to this season," added the Spaniard.

Rossi's team manager Davide Brivio was less specific in terms of the technical details, but is confident the new M1 will be 'up to the job'.

"In 2008, when we won everything: the Constructors' title, the Riders' title, the Teams' title, it provoked a great motivation and reaction from rival riders and factories and they must have all started working to produce a bike capable of beating us. We'll do the same," he said.

"This is the nice thing about motor racing: during the winter there is a lot of talk, because this or that rider is faster on this or that occasion, the fans and the journalists start passing judgments and making forecasts. Then, the facts disprove many of them and this is the most interesting part of our job.

"We haven't changed much with our bike, but we have made improvements in important sectors, trying to keep the level of competitiveness high. We'll see this at the first races and we hope that our bike will be up to the job. I believe it will be."