Sepang MotoGP test: Dani Pedrosa quickest on opening day

Pedrosa upped his pace drastically late on, blitzing the field with a 1m59.427s effort that left him three-and-a-half tenths clear of his nearest rival, Ducati's Andrea Dovizioso.

The test kicked off with the track soaked by rain, and the field were limited to wet-weather running in the opening hours as Tech 3 Yamaha's Johann Zarco set the initial pace.

LCR Honda's Cal Crutchlow was the first to try out slick-tyres as the eight-hour session approached halfway, and times began to quickly trickle down until Rossi emerged as the comfortable leader with a 2m00.799s.

The Italian spent almost an hour as the only rider below 2m01s, until he was joined by team-mate Maverick Vinales - who first went 0.041s quicker and then shaved more time to end up at 2m00.714s.

But the Yamaha pair were shortly surpassed by new leader Dovizioso, and then again by Pedrosa - the Honda man posting a 2m00.526s to go three hundredths clear at the top.

But Rossi improved further and looked likely to end the day quickest with his 2m00.233s lap before widespread improvements in the dying minutes shuffled him down to sixth.

Rossi was also overhauled by factory Ducati rider Jorge Lorenzo, who leapt up to third at the chequered flag, and Pramac Ducati duo Danilo Petrucci and Jack Miller, who completed the top five.

Pedrosa's Honda team-mate and reigning MotoGP champion Marc Marquez was seventh, ahead of Zarco and Crutchlow - the latter suffering a minor mid-session crash.

Pol Espargaro was the lead KTM in 10th, while Alex Rins logged the 11th-best time and fastest Suzuki rider. Aleix Espargaro was Aprilia's benchmark in 14th, over a second up on his new team-mate Scott Redding.

Vinales, who had dominated the pre-season last year, was only 13th, with both he and Rossi ending the day early.

Yamaha also fielded bikes for test riders Kohta Nozane and Katsuyuki Nakasuga as the team trialled an all-new aggressive winged fairing.

Marc VDS rider Tom Luthi, making his test debut with the team after he missed 2017 post-season running through injury, was 4.3s off the pace.