MotoGP title hopeful Jorge Martin led rookie sensation Pedro Acosta on the opening day of the three-day pre-season test at Sepang.
The Tuesday session marked the first official collective test day of the season, albeit with once absence among the full-timers as Pramac Ducati newcomer Franco Morbidelli is still sidelined following his scary accident while road bike testing at Portimao.
Morbidelli's team-mate Martin, who ended up a close second to Pecco Bagnaia in last year's title race, was comfortably first for most of the day's action, as the sole rider to dip below 1m58s.
His 1m57.951s is just under half a second off the MotoGP lap record at the venue, belonging to Bagnaia.
Acosta continued his assured start to life in MotoGP by placing second.
The Tech3 Gas Gas rookie did likely have his position inflated by the fact he'd run in the shakedown at the same track earlier this month - and the same is likely true for Yamaha rider Fabio Quartararo, who was just 0.008s behind Acosta in third.
VR46 Ducati newcomer Fabio Di Giannantonio piloted the best-placed of the 2023-spec Desmosedicis (as opposed to the 2024 bikes campaigned by the factory team and Pramac) to fourth place, with his three GP23 peers also in the top 10.
Alex Marquez (Gresini Ducati) was seventh, Marco Bezzecchi (VR46 Ducati) was eighth and Marc Marquez (Gresini Ducati) took ninth.
The younger Marquez and Bezzecchi both had crashes, while the elder Marquez had his start to the day compromised by technical issues.
Like in the shakedown, Johann Zarco was the lead Honda rider in 10th.
Fellow Honda newcomer Luca Marini said the brand's new RC213V was still only being exploited at "around 60%" - but reckoned he and his Honda peers had now settled on engine spec for the season.
Reigning champion Bagnaia begun the day with a tip-off on his outlap, and eventually ended up placing 16th - 11 places behind his factory team-mate Enea Bastianini.
Trackhouse Aprilia rider Raul Fernandez had what was described as a nasty high-side very shortly after Bagnaia, with his bike ending up on fire as a result. Fernandez, who covered just 21 laps before that, has been taken to hospital for checks.
Aprilia's lead rider was Maverick Vinales in sixth.
There were falls for Augusto Fernandez (Tech3 Gas Gas) and Jack Miller (KTM). Miller is still recovering from a fractured scaphoid sustained in motocross training in the off-season, but says he is not limited by the injury.
The grid will run for two more days at Sepang and will then have a two-day test at Lusail before the season-opening Qatar Grand Prix.