Stoner tested a new fairing - believed to offer more agility - and was fastest on both qualifying and race tyres, before rain put an early end to the test at 4:00 pm. The Australian was a fraction shy of his pole position pace on the soft rubber, but beat his best lap on race tyres.

"Today was reasonably busy - we didn't do a lot of laps but it was a very important test with some new equipment," said Stoner, after his 50 circulations. "We had a new fairing which went very well. We had good results with it and this is a positive thing for the rest of the season. We had also a lot of tyres to test and there were a couple of rears we were very happy with.

"We tested the new fairing in the afternoon and we didn't have new tyres so we used old ones: we were doing consistently 1min 58.7, 1min 58.9 already with 17 laps on the tyres so it was working quite well: we were happy with it and with everything we tested today. We are not sure exactly when we will use the new fairing at a race because I think we have to find a little bit more information but it's the right direction. I did a 1min 56.901 with a qualifying tyre, which is not so bad, so I'm pretty happy with the job I'm doing with my team," Casey concluded.

John Hopkins, second to Stoner on Sunday, was the only other rider to try a qualifying tyre but lapped some 0.64secs slower than the 21-year-old.

However, things were closer on race rubber with Repsol Honda's Nicky Hayden, third in the GP, just 0.17secs behind Stoner at the end of day one.

Testing concludes on Tuesday.