Valentino Rossi admits he is "worried" by the top speed deficit Yamaha faces compared to its MotoGP rivals after a subdued second day of Qatar pre-season testing.
On the penultimate day of 2019 pre-season running, Rossi ended up down in 19th place, 1.202s off the pace set by Suzuki's Alex Rins, while factory Yamaha team-mate Maverick Vinales was second quickest.
The seven-time premier class champion pinpointed the M1's lack of top speed as one of its biggest weaknesses, having logged a best speed of only 334.3km/h (207.7mph) on Sunday.
By comparison, Honda pair Marc Marquez and Cal Crutchlow [LCR] topped the speed charts at 346.1km/h (215.1mph).
"Unfortunately we are bit a slow in the straight," said Rossi.
"For some reason at Sepang, not very much. Here in Qatar we have a big gap, maybe because we struggle on the exit of the corner.
"I said last November we had two different engines [to try], I decided for one, and this is the engine.
"But the disadvantage here compared to Honda and Ducati, which is more than 10km/h in the straight, we are bit worried. At this moment, it's like this."
Explaining why he was so far down the timesheets on Sunday, Rossi added: "Yesterday [Saturday] we had a base setting, and I was not so bad, today we tried to improve, we tried some different settings and materials.
"But unfortunately we don't improve. It was a difficult day. I was always too slow. We are not happy."
While more upbeat about his day, Vinales pinpointed a lack of acceleration as an area where Yamaha is still giving away "some tenths" to its rivals.
"For sure the bike is working quite well, I think it's the best bike we had since two years ago," second-placed Vinales said.
"But the competitors made really good steps forward so we need to keep working, especially on the acceleration. Right now we lose quite a lot in that area."
He admitted the problem had been "not so much" in the previous test at Sepang, and said Yamaha would try "a different system" in Monday's session.
"At the moment the right way to focus is for sure on acceleration," he added. "We are very fast into corners and also in the corners but now we are losing on the exit."
When Vinales' comments about Yamaha being the strongest it has been since he joined the squad in 2017 were put to Rossi, he replied: "If he says [so], I'm agreed.
"Sincerely I suffer always a bit too much about rear grip, especially today. We try some different things for improving, because yesterday was the base and was not so bad.
"For me, we are not strong [enough] for winning. We have still a disadvantage compared to the best bike. I hope with all my heart that I'm wrong and Maverick is right!"
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