Following Sunday's Valencia MotoGP season finale, an official test session is being held at the circuit from Monday to Wednesday.
The test marks the first appearance for Cal Crutchlow at Ducati, Moto2 world champion Pol Espargaro at Yamaha Tech 3 and former title rival Scott Redding at Honda Gresini.
Redding plus Aspar's Hiroshi Aoyama and Nicky Hayden are riding the new Open class Honda Production Racer, with Hayden - who sat out Monday due to limited machine numbers - getting his first ride on the RCV1000R today.
The new privateer Forward Racing Yamaha is due to make its public debut on Tuesday in the hands of Aleix Espargaro and Colin Edwards. New world champion Marc Marquez and Repsol Honda team-mate Dani Pedrosa are also back on track after skipping day one.
Valentino Rossi is working with his new crew chief Silvano Galbusera for the first time, while former Aprilia Racing boss Gigi Dall'Igna is present in his new role as general manager of Ducati Corse.
The 2014 rules will see the Factory class bikes lose a further litre of race fuel relative to the Open class machines, raising the difference to four litres. The Open bikes must run the full control ECU system, while the Factory entries can use their own software.
Tuesday's track action began at 10am and concludes at 5pm.
for more pictures from the test...
1. Marc Marquez
ESP Repsol Honda Team (RC213V) 1m 31.008s
2. Alvaro Bautista
ESP Go&Fun Honda Gresini (RC213V) 1m 31.426s
3. Stefan Bradl
GER LCR Honda MotoGP (RC213V) 1m 31.437s
4. Dani Pedrosa
ESP Repsol Honda Team (RC213V) 1m 31.717s
5. Bradley Smith
GBR Monster Yamaha Tech 3 (YZR-M1) 1m 32.108s
6. Pol Espargaro
ESP Monster Yamaha Tech 3 (YZR-M1) 1m 32.874s
7. Nicky Hayden
USA Power Electronics Aspar (RCV1000R) 1m 35.251s
8. Michael Laverty
GBR Paul Bird Motorsport (PBM-ART) 1m 35.399s
9. Mike Di Meglio
FRA Avintia Racing (FTR-Kawasaki) 1m 35.969s
10. Randy De Puniet
FRA Paul Bird Motorsport (ART) 1m 37.544s
11. Scott Redding
GBR Go&Fun Honda Gresini (RCV1000R) 1m 38.103s
Fastest day one time:
ESP Yamaha 1m 31.257s
Official Valencia MotoGP records:
ESP Honda 1m 30.237s
Fastest race lap:
ESP Honda1m 31.628s
Fastest 2013 race laps by manufacturer:
ESP Honda 1m 31.628s
ESP Yamaha 1m 31.701s
USA Ducati 1m 32.764s
ESP ART 1m 33.323s
ESP FTR-Kawasaki 1m 33.551s
ITA Suter-BMW 1m 34.153s
AUS FTR-Honda 1m 34.815s
GBR PBM-ART 1m 35.886s