Australian Casey Stoner sealed the MotoGP title on his 26th birthday after his only title rival, Jorge Lorenzo, crashed in morning warm up at the weekend’s Australian Grand Prix.

The out-going champion severed part of his left ring-finger in the crash and was ruled unable to race at Phillip Island, the 16th round of the series.

It was the Aussie’s fifth-straight win on the Island, and Honda’s only title in the 800cc MotoGP era before the series changes to 1000cc in 2012.

Stoner is both the first and last 800cc world champion, sealing both titles in his debut year with a new team. In 2007 it was Ducati and 2011 Honda, making him just the fifth rider to achieve championships with two different manufacturers.

Neither factory Yamaha started the race after Ben Spies suffered a concussion in a 270kmh crash during qualifying on Saturday.

Stoner’s fellow Aussie Damian Cudlin was also unable to start in his first MotoGP race on home soil after he also suffered a nasty high-side during the blustery morning warm up.

Wind played its part in the crash-riddled qualifying and warm up sessions but it wasn’t a factor in seven-time champion Valentino Rossi’s crash on lap 14.

The Italian superstar lowsided his Ducati as he crested Lukey Heights and was unable to rejoin.

The remaining two Repsol Honda riders were locked in a battle for the final podium spot for much of the race, but with just three laps to rain began to fall and Andrea Dovioso left his soon-to-be ex-team-mate Dani Pedrosa in his wake.

Marco Simoncelli looked set for a comfortable second place but with rain falling Dovisoso overhauled the satellite Honda rider for second.

That ignited a tense battle for second as Stoner checked out to claim a historic win.

Simoncelli recovered second from Dovisoso, who will join Yamaha Tech 3 in 2012, with Pedrosa fourth.

CHAMPIONSHIP STANDINGS:

1       Casey Stoner, Repsol Honda Team, 325

2       Jorge Lorenzo, Yamaha Factory Racing, 260

3       Andrea Dovizioso, Repsol Honda Team, 212

4       Dani Pedrosa, Repsol Honda Team, 208

5       Ben Spies, Yamaha Factory Racing, 156

6       Valentino Rossi, Ducati Marlboro Team, 139

=      Marco Simoncelli, San Carlo Honda Gresini, 139

8       Nicky Hayden, Ducati Marlboro Team, 132

9       Colin Edwards, Monster Yamaha Tech 3, 109

10     Hiroshi Aoyama, San Carlo Honda Gresini, 94

11     Héctor Barberá, Mapfre Aspar Team, 77

12     Álvaro Bautista, Rizla Suzuki MotoGP, 67

13     Cal Crutchlow, Monster Yamaha Tech 3, 57

14     Karel Abraham, Cardion AB Motoracing, 56

15     Toni Elías, LCR Honda MotoGP, 55

16     Randy de Puniet, Pramac Racing Team, 49

17     Loris Capirossi, Pramac Racing Team, 36

18     Kousuke Akiyoshi, San Carlo Honda Gresini/LCR Honda, 7

19     John Hopkins, Rizla Suzuki MotoGP, 6

20     Shinichi Ito, Honda Racing Team, 3