MotoGP title leader Jorge Lorenzo led every minute of Friday morning's first practice for the Japanese Grand Prix at Motegi, a session that marked the return to action for Casey Stoner.
But Stoner's first track appearance since Indianapolis in mid-August saw the reigning double world champion suffer a technical problem after just a few turns - the engine appearing to shut down on his factory RC213V.
The Australian, still limping after ankle surgery to repair damaged ligaments and fractures, re-joined after ten minutes with his spare bike, and was fourth fastest - just under a second from Lorenzo - at the end of his first run.
Stoner - winner of four races this year and heading for retirement at the end of the season - then dropped back to sixth, before returning to fourth place on the timesheets (+0.758s) after a late push.
Factory Yamaha star Lorenzo meanwhile was quickest throughout the 45-minute session, albeit with Stoner's team-mate and title rival Dani Pedrosa finishing just 0.141s slower. Lorenzo leads Pedrosa by 33-points with four rounds to go.
Third quickest was Monster Yamaha Tech 3 rider Andrea Dovizioso (+0.361s). Behind Stoner and the only other riders within one-second of Lorenzo were Ben Spies (Yamaha), Cal Crutchlow (Tech 3 Yamaha) and Nicky Hayden (Ducati).
Satellite Honda riders Stefan Bradl (LCR) and Alvaro Bautista (Greisni) were an evenly matched eighth and ninth, with Valentino Rossi completing the top ten for Ducati (+1.228s).
Yamaha test rider Katsuyuki Nakasuga has been granted a wild-card entry for the factory in his home round.
The 31-year-old, who rode from 15th to sixth as a replacement for the injured Jorge Lorenzo at Valencia, finished the session in eleventh (+1.832s).
Satellite Ducati riders Hector Barbera (Pramac) and Karel Abraham (Cardion AB) completed the manufacturer riders, both over 2.5s from Lorenzo.
The stop-go circuit characteristics are tough on the CRTs, with Aleix Espargaro the leading privateer in 14th - but 2.7s from Lorenzo. Aspar team-mate Randy de Puniet was less than a tenth of a second slower.
Roberto Rolfo, drafted in to the cash-strapped Speed Master squad in place of Mattia Pasini for the remaining rounds, was 20th out of the 22 riders (+4.667s). Rolfo, who began the year in Moto2, is making his first MotoGP start since 2005.
Second free practice takes place this afternoon.
Japan is the first of three consecutive 'flyaway' rounds, prior to the Valencia season finale.
Free practice (1):
1. Jorge Lorenzo
2. Dani Pedrosa
3. Andrea Dovizioso
4. Casey Stoner
5. Ben Spies
6. Cal Crutchlow
7. Nicky Hayden
8. Stefan Bradl
9. Alvaro Bautista
10. Valentino Rossi
11. Katsuyuki Nakasuga
12. Hector Barbera
13. Karel Abraham
14. Aleix Espargaro
15. Randy De Puniet
16. Colin Edwards
17. Michele Pirro
18. Yonny Hernandez
19. James Ellison
20. Roberto Rolfo
21. Ivan Silva
22. Danilo Petrucci