Valentino Rossi ended the first day of the final major MotoGP test of the year at the top of the timesheets.
Rain brought the decrease in lap times to a temporary halt after lunch, at which point Rossi was fastest ahead of John Hopkins, and Yamaha team-mate Colin Edwards.
Rossi commented at the end of the day: "Unfortunately we only had time for a few laps before the bad weather stopped us just when we were about to begin to test some different things, but anyway we have made a good start.
"Even though the bike is clearly going well for both Colin and I at the moment, we know that we have a lot of work to do and so these next two days are going to be very important to us."
Dani Pedrosa was the leading Honda rider with Nicky Hayden missing the test to have a shoulder injury operated on.
Pedrosa was fourth quickest, from Loris Capirossi on his Ducati GP7 on Tuesday, day one of the three day tests.
Chris Vermeulen was sixth, Marco Melaqndri seventh, Casey Stoner eighth, Shinya Nakano ninth in his Honda debut, and Jeremy McWilliams just a second behind the Honda V4 on the all-new Ilmor.
Valentino Rossi 1:41.74
John Hopkins 1:42.16
Colin Edwards 1:42.29
Dani Pedrosa 1:44.03
Loris Capirossi 1:44.30
Chris Vermeulen 1:44.39
Marco Melandri 1:44.87
Casey Stoner 1:45.57
Shinya Nakano 1:46.20
Jeremy McWilliams 1:47.21