Maverick Vinales started his collaboration with Yamaha by topping Day 1 of the MotoGP post-season testing at Valencia ahead of the crashing Valentino Rossi and Ducati debutant Jorge Lorenzo.
Vinales took the lead during the penultimate hour with a time of 1m30.930s, beating Rossi's time, which had been the benchmark for most of the session, by two hundredths.
The test kicked off with Lorenzo opting for an early start with Ducati, the Spaniard taking first place with an unrepresentative time in the 1m37s region.
Marc Marquez soon took over and stayed in the lead for a whole hour before he was demoted, first by teammate Dani Pedrosa and then Rossi.
The Italian first appeared on track with his 2016-spec bike nearly two hours into the session, his benchmark flyer quickest by six tenths.
He soon reemerged from the pits again with the new engine and, after two stints, crashed out, becoming the first rider in the test to do so.
Despite missing most of the session, Rossi stayed on top of the timesheets for almost four hours before his new teammate Vinales went narrowly quicker.
As the final stages under cooling conditions were more about crashes than improvements, it was Vinales completing the day in first.
The ex-Suzuki rider spent the day familiarising himself with the 2016-spec Yamaha and didn't test the team's new bikes, unlike Rossi, who was back out on track during the final hour with a new chassis.
Lorenzo followed the Yamaha duo one tenth adrift, setting his time with just 40 minutes left after spending much of the day working on his seating position.
He was less than a tenth quicker than fellow Ducati factory rider Andrea Dovizioso, the latter only taking fifth as the duo was split by Marquez.
Cal Crutchlow became the second quickest Honda in sixth, the Briton being among several others, including seventh-placed Andrea Iannone, to crash towards the end of the session.
The Italian's first day with Suzuki, which did not bring a new chassis and instead focuses on engine development in Valencia, was overshadowed by a heavy crash at Turn 10, the bike hitting the tyrewall hard.
Pramac's Scott Redding and Avintia's Hector Barbera were eighth and ninth respectively, both riding on 2016-spec Ducatis, with Dani Pedrosa rounding out the top 10, less than four tenths off the pace.
Redding's teammate at Pramac Danilo Petrucci missed the day due to family issues and was replaced by Michele Pirro, who was 13th with a Ducati claimed to be of a spec somewhere between the GP16 and GP17.
Aleix Espargaro was the quickest of the two Aprilias in 14th while the KTMs of Pol Espargaro and Bradley Smith were 19th and 20th respectively.
Both Espargaro brothers crashed during the session, as did Loris Baz and Aprilia's MotoGP newcomer Sam Lowes.
In addition, Aprilia and Suzuki test riders Eugene Laverty and Takuya Tsuda also fell.
Jonas Folger ended up as top rookie in 16th, just ahead of Tech 3 teammate and two-time Moto2 champion Johann Zarco.
Moto3 frontrunner Francesco Bagnaia completed nine laps in the beginning of the session as a reward for winning a bet against Aspar sporting director Gino Borsoi.
Day 1 results