Having qualified on the MotoGP front-row 13 times during his rookie season, more than any other Yamaha rider, Fabio Quartararo is now expected to be found near the top of a flying-lap timesheet.

The Petronas rider was duly classified second quickest to Maverick Vinales on day one of testing at Jerez, but the 0.754s gap to the factory Yamaha rider was unusually large.

The young Frenchman, who took the first of six MotoGP pole positions at the Jerez circuit in May, later explained that a combination of new parts, red flags and rain meant he hadn't been able to show his usual speed.

"We already know why," Quartararo said of the sizeable difference to Vinales. "He already made two days of testing in Valencia with the new bike and we know Maverick is a really fast rider.

"For us, it was the first time that we tried this new prototype engine and of course it's never easy to go fast when you have new things on the bike. It was more to understand.

"We also never made one run really pushing for two laps like we do normally when we are on top of the screens.

"When I put the new tyre there was a red flag, so the tyre had already done two laps. Then you go out again and it was raining. Then the third time I went on track and made the lap time, but each time you go out-and-in the tyre drops.

"But we made a really good pace with old tyres, I think with 30 laps on the tyres I was one or two tenths from my fastest lap. I think this is really positive, also for our bike."

Although Quartararo and team-mate Franco Morbidelli had a new engine, assumed to be the same as that given to Vinales and factory team-mate Valentino Rossi at Valencia last week, they were without the revised airbox or latest frame used by the Monster riders.

"We ran most of the day with this new engine," Quartararo confirmed. "It was really difficult to understand because we make all the year with the same bike and then when you get a new engine you need to work on things like the electronics and that was mainly the plan of today.

"Tomorrow will be the same, trying to get a better feeling and of course it's important that first of all we have a base. We are not exactly comfortable like with last year's bike yet. Now the pace is good, but I'm not as smooth as before."

Quartararo had been fastest on day one of last week's Valencia test, when he tried Yamaha's end-of-season chassis developments for the first time, then a close second to Vinales on day two.

Morbidelli was fifth quickest (+0.986s) on Monday at Jerez, with Rossi 14th (+1.628s).

"I tried the new spec and I had a new feeling on it," Morbidelli said of the new engine. "It seems a bit faster. It seems a bit more angry in 5th and 6th gear and this is what we wanted. Now we have to analyse what is better and what is worse.

"The engine has a different behaviour, especially on the straight and then approaching the corner, so it's a matter adapting yourself and also adapting everything to the new engine."

But it "still has a Yamaha soul, so it's really smooth. Yamaha managed to keep the corner speed, I am happy with the job they have done."

A further engine evolution is expected for the Sepang test in February.