Yamaha MotoGP launch: 2018 design revealed with Rossi and Vinales

The bike, sporting a familiar blue paint scheme with prominent branding - now white as opposed to green - from title sponsor Movistar, was unveiled in the Matadero Madrid modern art centre.

Rossi will be entering the second season of his current two-year deal, while Vinales announced during the event that he has signed a new contract and will now remain with Yamaha until at least 2020.

Yamaha last took both the riders' and manufacturers' titles back in 2015, as Jorge Lorenzo beat Rossi to the title. The year after, the works outfit couldn't defend either crown, although it did top the teams' classification.

Last season marked the arrival of Vinales as replacement for Ducati-bound Lorenzo, but while the newcomer won his first two races with the team, both his and Rossi's title challenges faded as they struggled to get the most out of the 2017-spec bike - leading to Yamaha's worst MotoGP season in many years.

"We are quite convinced that if we can make the bike more consistent, for both our riders, we can challenge for the title," said team manager Massimo Meregalli.

"That is our main goal for this season."

The team ran its '16 and '17 chassis back-to-back throughout post-season testing, and Rossi later stated it was the former that would serve as the basis for this year's version.

Yamaha's on-track preparations for the upcoming season will continue on January 28-30, during MotoGP's first official pre-season test at Sepang.

Meregalli added: "It has been really important that last year we could test in Valencia and then in Sepang, we could compare the same items in two different circuits, two different conditions.

"At the end of these five days we could decide the base of the bike that Valentino and Maverick will start testing in Sepang in three days.

"We will need to confirm what we found in November, and then we will start developing the bike with the new parts that are coming from Japan.

"We will work on the electronics - that we couldn't do in November, so I expect an improvement in that area.

"Last year, as you know, we suffered a lot with the wear of the tyre. This is our main goal, to solve it."