Following Sunday's season-ending Valencia Grand Prix, a two-day post season MotoGP test began at the circuit on Tuesday.
However rain fell shortly after the track opened and the circuit has remained wet since. Alvaro Bautista, whose Honda is now sponsored by 'Go & Fun', set the fastest lap time just before the rain.
The test marks Valentino Rossi's first Yamaha laps since 2010, while Rossi's Ducati replacement Andrea Dovizioso is making his Desmosedici debut.
Rossi did not complete a flying dry lap.
Moto2 stars Marc Marquez (Honda) and Bradley Smith (Tech 3 Yamaha) are due to make their first MotoGP appearances - fellow 600cc star Andrea Iannone having previously tested for Ducati.
Former MotoGP racer Loris Capirossi rode Smith's bike this morning.
Ben Spies, moving from Yamaha to Ducati for 2013, is not present due to recent surgery. His place is being taken by new Ducati test rider Michele Pirro.
Testing concludes on Wednesday evening, although Yamaha may switch to Aragon for day two.CLICK HERE
for extensive picture coverage from the Valencia MotoGP test...
1. Alvaro Bautista
ESP Honda Gresini (RC213V) 1m 35.936s
2. Loris Capirossi
ITA Yamaha Tech 3 (YZR-M1) 1m 35.954s
3. Stefan Bradl
GER LCR Honda MotoGP (RC213V) 1m 36.198s
4. Andrea Dovizioso
ITA Ducati Team (GP12) 1m 39.868s
5. Hiroshi Aoyama
JPN Avintia (FTR-Kawasaki CRT) 1m 42.239s
6. Valentino Rossi
ITA Yamaha Factory (YZR-M1) 1m 44.158s
7. Karel Abraham
CZE Cardion AB Motoracing (ART CRT) 1m 47.129s
8. Randy De Puniet
FRA Aspar (ART CRT) 1m 48.794s
9. Claudio Corti
ITA Forward Racing (FTR-Kawasaki CRT) 1m 49.128s
10. Aleix Espargaro
ESP Aspar (ART CRT) 1m 51.015s
(2/2) Colin Edwards
USA Forward Racing (FTR-Kawasaki CRT) No Time Hector Barbera
ESP Avintia (FTR-Kawasaki CRT) No Time Danilo Petrucci
ITA Came IodaRacing (Suter-BMW CRT) No Time Dani Pedrosa
ESP Repsol Honda (RC213V) No Time Andrea Iannone
ITA Pramac Racing (GP12) No Time Cal Crutchlow
GBR Yamaha Tech 3 (YZR-M1) No Time Michele Pirro
ITA Pramac Racing (GP12) No Time Shane Byrne
GBR Paul Bird Motorsport (ART CRT) No Time Nicky Hayden
USA Ducati Team (GP12) No Time Marc Marquez
ESP Repsol Honda (RC213V) No Time Jorge Lorenzo
ESP Yamaha Factory (YZR-M1) No Time Official Valencia MotoGP records:Best lap: Dani Pedrosa
ESP Honda 1m 30.844s
(2012)Fastest race lap:Casey Stoner
AUS Ducati 1m 32.582s