Australian world MotoGP champion Casey Stoner has clocked the fifth fastest time on the second day of testing at Sepang in Malaysia despite admitting he is not fully fit yet.

Ducati rider Stoner suffered a bad fall while doing post-season testing at Jerez in Spain, but has recovered sufficiently to demonstrate he will be a force on the circuit once again when the new season begins in March.

"When I think that I was still suffering from pain in my shoulder only a week ago, I have to be really happy with how things are going," said Stoner.

"I'm still not 100 per cent but I'm able to ride much better than I expected. Now I know that I can begin making the right preparations to be ready for the start of the season," he said.

Stoner clocked a time of 2:01.638 around the Sepang circuit to end up narrowly behind fastest tester Randy de Puniet from Honda (2:01.139), Yamaha's Colin Edwards (2:01.327) and the Fiat Yamaha pair of former world champ Valentino Rossi (2:01.437) and his rookie team-mate Jorge Lorenzo (2:01.583).

It was not all plain sailing for Stoner on day two, however, as his team was forced to deal with some minor technical issues on the new Desmosedici GP8 bike that Stoner hopes will take him to a second successive world championship.

"After lunch we started a long run and everything went great for the first ten laps," explained Stoner.

"I had a good pace together, inside lap record, but then we started to get a strange vibration from the rear that was upsetting the bike in a couple of braking areas."

"I preferred to stop to try and work out what it was and we found a small problem with the clutch."

"We went back out again on the same tyres but I started to get cramps in my left arm, so we decided it was better not to push it too much and to sit the rest of the day out," he said.

Meanwhile, after posting the third-best testing time on day one, Stoner's Australian compatriot Chris Vermeulen from Rizla Suzuki could only manage the 12th-fastest time on Wednesday, posting 2:02.371 as he narrowly edged out Kawasaki's Anthony West (2:02.579).

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