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, Nicky Hayden at Aspar, Moto2 world champion Pol Espargaro at Tech 3 and former title rival Scott Redding at Gresini.
Redding, Hayden and Hiroshi Aoyama 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 made its public debut on Tuesday in the hands of Aleix Espargaro and Colin Edwards, when new world champion Marc Marquez and Repsol Honda team-mate Dani Pedrosa were also back on track after skipping day one.
Marquez led for almost the entire day, lapping comfortably the new official race lap record. The 20-year-old - riding with a special helmet design - saved the 2014 RC213V with his knee and elbow after a big lowside moment at turn six, shortly after 1pm.
Like many riders, Marquez made a last push - clocking his best time of the day on the 75th of 76 laps. Yamaha's title runner-up Jorge Lorenzo moved into second, while Pedrosa reclaimed third from LCR's Stefan Bradl.
Valentino Rossi was 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.
Former Aspar rider Randy de Puniet made his PBM debut on Tuesday, as the British team seeks to reach an agreement with Aprilia for 2014. The test was briefly red flagged due to a late fall for PBM regular Michael Laverty.
The 2014 rules will see the Factory bikes lose a further litre of race fuel relative to the Open 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.
The final day of testing begins at 10am on Wednesday, but some teams - including Yamaha - are expected to pack up this evening.
for more pictures from the test...
1. Marc Marquez
ESP Repsol Honda Team (RC213V) 1m 30.536s
2. Jorge Lorenzo
ESP Yamaha Factory Racing (YZR-M1) 1m 30.768s
3. Dani Pedrosa
ESP Repsol Honda Team (RC213V) 1m 30.948s
4. Stefan Bradl
GER LCR Honda MotoGP (RC213V) 1m 30.990s
5. Alvaro Bautista
ESP Go&Fun Honda Gresini (RC213V) 1m 31.208s
6. Bradley Smith
GBR Monster Yamaha Tech 3 (YZR-M1) 1m 31.397s
7. Valentino Rossi
ITA Yamaha Factory Racing (YZR-M1) 1m 31.414s
8. Andrea Dovizioso
ITA Ducati Team (GP13) 1m 31.661s
9. Pol Espargaro
ESP Monster Yamaha Tech 3 (YZR-M1) 1m 31.836s
10. Andrea Iannone
ITA Energy T.I. Pramac Racing (GP13) 1m 31.844s
11. Cal Crutchlow
GBR Ducati Team (GP13) 1m 32.114s
12. Michele Pirro
ITA Ducati Test Team (GP13) 1m 32.473s
13. Nicky Hayden
USA Power Electronics Aspar (Honda RCV1000R) 1m 32.576s
14. Yonny Hernandez
COL Ignite Pramac Racing (GP13) 1m 32.800s
15. Aleix Espargaro
ESP NGM Forward Racing (FTR-Yamaha M1) 1m 32.847s
16. Colin Edwards
USA NGM Forward Racing (FTR-Yamaha M1) 1m 33.149s
17. Michael Laverty
GBR Paul Bird Motorsport (PBM-ART) 1m 33.672s
18. Randy de Puniet
FRA Paul Bird Motorsport (ART) 1m 33.833s
19. Scott Redding
GBR Go&Fun Honda Gresini (Honda RCV1000R) 1m 34.541s
20. Mike di Meglio
FRA Avintia Racing (FTR-Kawasaki) 1m 34.618s
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