Fabio Quartararo completed a clean sweep of the Sepang MotoGP pre-season test after topping the third day, while Marc Marquez crashed again.
Quartararo took delivery of Yamaha's 2020-spec YZR-M1 on Saturday, setting the pace immediately, and used the bike to once more end up fastest on Sunday.
The Petronas SRT rider guided the bike to a 1m59.787s early in the first hour of running to claim top spot back from Pramac Ducati rider Jack Miller.
Miller would quickly depose Quartararo, though, before Suzuki's Joan Mir moved to the top of the times with a 1m59.848s after the first 10 minutes.
By the end of the first hours Quartararo had returned to the top of the timesheets with a test-best effort of 1m58.349s, having tussled with LCR's Cal Crutchlow briefly for supremacy on the timing screens.
Quartararo's lap would go unchallenged as the day wore on, with much of the field ending the session early.
Crutchlow - who said on Saturday that the Honda's turning woes had worsened - trailed Quartararo by 0.082 seconds, with Alex Rins completing the top three on the first of the Suzukis.
Pramac's Francesco Bagnaia was top Ducati runner in fourth, beating his mentor Valentino Rossi by 0.039s in fifth.
Yamaha debuted its version of the holeshot device. Both Rossi and fellow works team rider Maverick Vinales had one each, as did test rider Kohta Nozane.
The team also trialled some aerodynamic add-ons to the front of the fairing on the M1s of Rossi and Vinales.
Danilo Petrucci was seventh on the first of the works Ducatis ahead of KTM's Pol Espargaro, Miller and Espargaro's Aprilia-mounted brother Aleix.
He was able to put in a long run on Sunday on the brand new RS-GP, having expected not to owing to the freshness of the Aprilia's engine.
A 12-lap stint of mid-1m59s showed the promise of the new bike over race distance, though Espargaro was unable to get that far after an exhaust issue cut his run short.
Mir completed the top 10, edging ahead of Tech3's Miguel Oliveira, while Marquez shadowed him in 12th after suffering his second fall of the test.
The Honda rider slid off his bike at the last turn late in the day, but walked away unscathed.
Andrea Dovizioso was a low-key 14th on his works Ducati, though was only 0.5s off the pace on a day when the top 18 were all within a second.
He headed Johann Zarco, who found almost a second compared to his Saturday best as he continues to adapt to the Avintia Ducati GP19.
Maverick Vinales spent much of his day comparing both of his 2020-spec M1s and trying race runs, and was 18th at the chequered flag.
Yamaha test rider Jorge Lorenzo completed 44 laps on his second day on the bike.
He lapped 1.3s off Quartararo's pace in 20th having spent the entirety of his time on last year's M1.
Testing resumes in Qatar on February 22-24.
Sepang day three times
Get unlimited access to the world’s best motorsport journalism with Autosport Plus