Thailand MotoGP: Valentino Rossi cannot explain Yamaha improvement

Rossi and team-mate Maverick Vinales filled the top two spots in the first practice session and Vinales was only beaten by Ducati's Andrea Dovizioso in the afternoon running.

Rossi argued that the pace was "not the reality" of the troublesome Yamaha M1 that was expected to be ill-suited to the Buriram circuit.

However, the Yamaha rider was unable to give a reason for the sudden upturn in form considering its struggles in the previous race weekend at Aragon.

"Aragon was a disaster because we didn't have any grip," said Rossi, who ended the second practice session in ninth.

"Here on paper we have to suffer but today less than what we expect, so we are a bit more competitive.

"We go on the track and it looks like the track has more grip so you can push more.

"Aragon was very difficult. But why [are we better here]?

"The problem is that we don't know. Also Yamaha doesn't know.

"This morning FP1 was fantastic because we were first and second but also because a lot of top riders didn't put on the new tyre.

"This [improvement] is not the reality but anyway we can stay in the top 10 to try to go directly into Q2 and try to make a better race, better result, compared to Aragon.

"The situation is a bit difficult because at the end the bike is the same, but today we suffer less and, sure, it is better.

"For some reason we have a lot of difference between the good tracks and the bad tracks.

"It is like we suffer more than the other bikes, the other bikes are more balanced, always the same."

Vinales said that the "surprising" form in Thailand was positive, as it can inform development for 2019.

"We try some things that we should have tried many months ago," said Vinales. "The work, it's been done well. I'm actually happy.

"As I said, sometimes the work wasn't good, today was really good. "We did good work from FP1 to FP2, good changes.

"I can ride very precise, especially on the weight balance, which was very important today to improve a little bit the braking, a little bit on the acceleration, and finally we did it.

"This test is also important for 2019 and I am actually happy and pleased with the result of today. Let's see tomorrow."