Rossi unsure if Yamaha will have 2018 MotoGP bike for Valencia test

After Maverick Vinales was finally eliminated from title contention last weekend at Phillip Island, Yamaha's full focus is likely to have shifted to its 2018 bike.

It debuted a prototype 2018 frame at Silverstone, but the final version is likely to be different as it will need to be adapted to a revised specification of engine, which is frozen during the season.

Rossi said there was a chance the introduction of the new machine could be delayed, as engineers continue to evaluate new solutions during the remaining rounds of the season at Sepang and Valencia.

"We don't know yet if the new bike will be in the Valencia test or if it will only arrive in February [for the first test of 2018]," admitted Rossi.

"It depends very much on how these last two races go.

"Of course the faster the new bike comes the better, but it's not a big deal.

"The Japanese have so many ideas, so there are things to do and it will be very important to see if we can do some good laptimes and be competitive even on used tyres in these last two races."

The 2017 M1's biggest weakness has been a lack of rear traction, which has left Rossi and Vinales uncompetitive on stop-start track layouts and low-grip surfaces like Jerez and Barcelona.

Yamaha enjoyed its best showing for some time last weekend at the more flowing Phillip Island track, but Rossi said the team needed to understand whether this was a one-off or a sign of real progress.

"These are two very important races for me," he said, "because we have to decide what to do with the development of the bike.

"Also it's fundamental to confirm how well we did at Phillip Island. Otherwise it's a big problem and we need to think hard.

"Sepang and Valencia are two tracks that wear out the rear tyre a lot, so they will help us to understand how we are doing."