Yamaha's Maverick Vinales beat 2018 MotoGP world champion Marc Marquez by 0.302 seconds in a rain-hit first day of 2019 pre-season testing on Tuesday in Valencia.
Overnight rain left the Ricardo Tormo circuit damp as Tuesday's test was given the green light, meaning a no wheels were turned for the first two hours.
KTM newboy Johann Zarco was the first to venture out on circuit at 12:15 local time, and set the benchmark time at 1:34.547s before returning to pitlane after three laps.
With just over four and a half hours left, a few more riders made their way onto the circuit, with Zarco's initial pacesetting lap beaten by Ducati test rider Michele Pirro with a 1:33.347s, with the sister KTM of Pol Espargaro 0.096s adrift in second.
With a little over four hours remaining, Jorge Lorenzo began his first run on the Honda, and was 11th at the end of it, 2.8s adrift of Ducati replacement Danilo Petrucci.
Former team-mate Andrea Dovizioso soon hit the top of the times on the 2018 Desmosedici, before Marc Marquez usurped him on one of his two developmental RC213Vs with a 1:32.022s.
Dovizioso and Marquez traded top spot in the afternoon, with the latter edging clear with a 1:31.718s.
However, Vinales – now running the number 12 instead of 25 – set what would become the best lap of the day of 1:31.416s, as he tested among other things a new engine on Tuesday.
The arrival of rain with around 90 minutes left of the session meant Vinales' time would not be bettered, while no-one would take to the circuit again.
Vinales' Yamaha teammate Valentino Rossi was third quickest, 0.127s further adrift of Marquez, while Dovizioso headed LCR stand-in and Honda test rider Stefan Bradl by just 0.001s.
Franco Morbidelli sat as top Yamaha runner early on as he made his M1 debut aboard the '18 bike for new outfit Petronas SRT, '18's top rookie ending the day sixth ahead of Aprilia's Aleix Espargaro, Petrucci, Pol Espargaro and Pirro – who crashed in the afternoon.
Debutant Francesco Bagnaia was 11th and top Pramac runner on the GP17, while teammate Jack Miller – trialling the '19 prototype – was 14th having had to park up early with a technical issue.
The Australian was shadowed by Joan Mir, who took part in his first official test as a Suzuki rider having completed a brief private outing last week.
He headed Avintia's Tito Rabat, making his first MotoGP appearance since breaking his leg at Silverstone and was impressively just 1.4s off the pace on his first ride of the GP18.
Early leader Zarco ended up 17th ahead of Lorenzo and Aprilia's Andrea Iannone, while Tech3 KTM duo Hafizh Syahrin and Miguel Oliveira completed the 25-rider field, with the latter's fellow rookie Fabio Quartararo [Petronas SRT] 23rd behind Yamaha test rider Jonas Folger.
