Andrea Dovizioso set the fastest lap time during a mixed Friday free practice session at Le Mans, during an hour long session split almost exactly in half by rain.

Friday's session was the first of the 2009 season to last for one hour, after a recent rule change reversed the switch to 'cost-cutting' 45-minute sessions.

However, the fast changing Le Mans weather did its best to negate the change, with rain arriving shortly after the midway point and sending all riders into the pits while bikes were adjusted to wet weather settings.

Most riders completed some wet laps during the last ten minutes, but conditions were tricky; the track was too wet for slicks but parts of the track had only a light sprinkling of rain.

Dovizioso had put his Repsol Honda on top of the timesheets just moments before the rain arrived and the change in conditions kept the young Italian in P1 by 0.058sec over Ducati's Casey Stoner.

Stoner, who dropped out of the podium fight at Le Mans last season after a technical problem late in the race, appeared to suffer some form of problem during the opening stages of Friday's session - the Australian sitting 18th and last, having completed five laps, after 20 minutes.

But the 2007 world champion got into his stride thereafter, moving up to seventh place on his sixth lap, then taking first position from home hero Randy de Puniet on his following circulation.

Stoner had described his Ducati as being difficult to muscle around the tight corners in previous seasons, but hoped the carbon-fibre GP9 - and electronic changes - would help in that regard.

de Puniet - now riding with Elf in place of the former Playboy logos on his LCR Honda - nevertheless remained in the top three until the arrival of the rain, with the Frenchman's best lap a mere 0.157sec behind Dovizioso.

2007 Le Mans winner Chris Vermeulen was ranked fourth, 0.165sec from the top, for Rizla Suzuki, and the Australian will be a favourite to repeat his wet weather victory should similar conditions occur on Sunday.

The Suzukis are riding without Rizla logos this weekend, due to France's strict laws regarding the advertising of tobacco-related products.

Dani Pedrosa, joint third in the championship with Jorge Lorenzo after second place at Jerez, completed a top five covered by just 0.340sec.

Reigning world champion and 2009 world championship leader Valentino Rossi, chasing his 99th grand prix victory this weekend, had been hoping that a late set-up breakthrough at Jerez would carry over to Le Mans, but the results seemed to indicate otherwise.

At a circuit famously suited to Yamaha machinery, and where Rossi led an M1 one-two-three last season, The Doctor was only eighth at the half way stage, but snatched sixth from team-mate Lorenzo just before the rain arrived to at least be the fastest Yamaha.

Eighth behind the factory Yamahas was Marco Melandri, winner at Le Mans in 2006 and fresh from an excellent fifth place for Hayate at Jerez. Melandri, who exactly matched Lorenzo's lap time, could also spring a surprise in the wet, having finished second to Vermeulen in the wet 2007 event.

The top ten was completed by Loris Capirossi (Suzuki) and Colin Edwards, the Texan once again the leading Monster Yamaha Tech 3 rider at the start of the squad's home event, but this time only two places ahead of team-mate James Toseland.

Gresini Honda's Toni Elias was between the Tech 3 riders, with top rookie Mika Kallio just behind Toseland to once again be the second best Ducati rider after Stoner.

Another former Le Mans winner, Sete Gibernau, was 14th for Francisco Hernando Ducati, while Nicky Hayden's first track session with new crew chief Juan Martinez resulted in 15th place on the factory GP9.

Alex de Angelis (Gresini Honda), Yuki Takahashi (Scot Honda) and Niccolo Canepa (Pramac Ducati) completed the 18 rider field.

Rain had also soaked the circuit in the morning, to be followed by sunshine and the changeable weather conditions are expected to continue throughout the French GP weekend, with Saturday tipped to be the bleakest of all.

During the dry part of Friday's session, Bridgestone's softer compound tyres were marked with a white line on the side of the tyre.

Friday practice:

1. Dovizioso
2. Stoner
3. de Puniet
4. Vermeulen
5. Pedrosa
6. Rossi
7. Lorenzo
8. Melandri
9. Capirossi
10. Edwards
11. Elias
12. Toseland
13. Kallio
14. Gibernau
15. Hayden
16. de Angelis
17. Takahashi
18. Canepa