Quartararo used the 2020-spec M1 on the second and third day of the first MotoGP pre-season test of the year at Sepang.
He topped both days - after being fastest with his old bike on the opening day -, ending the test with a 1m58.349s, nearly two tenths quicker than second-fastest Yamaha of Valentino Rossi.
But afterwards Quartararo called for more work and time with the bike as his overall feeling with it is not yet optimal.
"I am not feeling 100 percent comfortable with the bike so we need to work and understand why, also check the data with the factory [team]," said the Frenchman.
"It's not really a [single] problem, it's overall of everything, braking area, electronics, the drive, the grip, a little bit of everything. It is quite difficult but with the team we'll analyse."
Apart from one-lap pace, Quartararo also looked competitive in long-run performance, and reckoned that Yamaha already gained a couple of tenths even though the top speed is still not on par with rivals.
"Really happy because we make the long run in 55 degrees on the track, was the worst of the two days and we manage to get into the 1m59s, 2m00s really lows so quite happy about the pace of today.
"It is the first long run that we do with the bike, we need to work with the electronics. Really not easy, but we still have one more test before the race."
"Last year we saw that the problem was the top speed. We see with factory, we are still really far from top speed which is something we need to check in Qatar.
"But yes, I think with this [bike] we can already win some tenths."
Lorenzo denied 2020 bike mileage
Test rider Jorge Lorenzo appeared on track for the first time during the official test on Sunday, the Spaniard also having rode for a day during the shakedown.
Lorenzo was 20th in the timesheets, having done 46 laps. He only rode the 2019 Yamaha, which he was happy with, but noted that it has two or three weak points.
"It's a nice feeling, as I felt the first day, the bike didn't change so much, luckily or unluckily, depends on how you see," Lorenzo said.
"The bike is still very competitive, very easy for the rider especially if you are a smooth rider.
"These two days I see some two or three weak points that we need to work a lot for the future that we need to focus on but also we have a lot of strong points and we keep these strong points that we got in the past, this is a good thing.
"Unfortunately for some reasons, Yamaha decided not to give me the new bike to try.
"They were thinking about it but finally decided not to let me try. We didn't have the time, or enough pieces to have one new bike for me."
Additional reporting by Lewis Duncan and Oriol Puigdemont
Jorge Lorenzo, Yamaha Factory Racing
Gold and Goose / Motorsport Images