Sepang MotoGP test: Yamaha's Valentino Rossi tops first day

The morning's very hot weather - with track temperature nudging 60 degrees centigrade - left the circuit much more slippery than it had been for the opening test three weeks earlier.

All the quickest times were set in the opening hours before the weather got warmer still, before conditions broke mid-afternoon when lightning and heavy rain arrived.

Rossi's early 2m00.414s lap for Yamaha therefore stood as the best of day one, putting him 0.129 seconds ahead of Dani Pedrosa's Honda.

Yamaha has brought a major gearbox upgrade to this test as it tries to reduce the advantage Honda's seamless shift system had last year.

Espargaro brothers Pol and Aleix were next up, as the latter showed strong pace on the new Suzuki, although his day was also interrupted by a crash.

Rookie Maverick Vinales also got Suzuki into the top 10 as he took ninth on the sister bike.

Jorge Lorenzo and Marc Marquez made low-key starts in fifth and sixth, the latter hampered by brake disc problems, ahead of British duo Cal Crutchlow and Bradley Smith.

Ducati's eagerly-awaited new GP15 bike made its debut, although Andrea Dovizioso and Andrea Iannone also had interim 2014 versions available too.

Both set their best times on the GP14.3 as tentative work began on the bike Ducati is counting on to end its win drought.

The test continues for three more days, with Thursday reserved for Michelin tyre testing ahead of its 2016 return.

That session will be the factory MotoGP riders' first chance to try the new rubber, as Michelin running has been restricted to test riders so far.

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