By Peter McLaren

Valentino Rossi had a simple explanation for his scorching day one pace at Sepang; his bike is better than at the last test - and so is he!

With Fiat Yamaha not attending the Phillip Island outing, Rossi's only previous track appearance of 2008 was also at Sepang - at the end of January - when he had been just sixth fastest, over one-second behind Nicky Hayden when both were on qualifying tyres.

But Rossi - sharing the track with just eight other riders - ramped up the pace quickly on his February return, setting an impressive 2mins 1.444secs on race tyres before punching out a stunning 2mins 0.300secs - the best lap seen at Sepang this winter and 1.5secs under Dani Pedrosa's 2007 pole time - with a late qualifying tyre attack.

Although Rossi's best race-tyre lap was also significantly faster than he'd recorded at the January test, he still needs to find a further 0.48secs to reach the best race-tyre lap of the winter, a 2mins 0.964secs set by world champion Casey Stoner.

With Stoner's Ducati team sitting out this week's test, and Pedrosa - the 2007 world championship runner-up - sidelined by injury, Rossi will never know what two of his closest rivals would have been capable of.

Nevertheless, Rossi revealed that Tuesday marked the first time he'd starting adjusting the M1 around his new-for-2008 Bridgestone tyres - and that he was also riding better than at the first test.

"Today was a good day of work," declared Rossi, whose best race-tyre lap was half a second clear of Hayden. "We started well this morning and made a good step this afternoon. The biggest improvement was found by working on the front tyre. We fixed a lot of vibration which had given me a problem at the first test, so we were able to go very fast on the race tyre.

"Last time we were here we worked just on the tyres. We did a base setting then worked on the tyre, because it was the beginning. Now we have clear ideas so we've started working on the bike. We've modified the balance, the setting, the stiffness - more up, more down - and we have some positive feeling.

"I am also better than last time we were here," confirmed the former five-times MotoGP world champion. "I had to stop training for a month [due to his fractured hand, sustained at the Valencia season finale] so I was not at the maximum before. This time I am in a better shape, because I have been able to train."

But one thing that hasn't changed is his M1's pneumatic-valve engine, which Rossi says is the same as at the first 2008 test.

"The [pneumatic] engine is the same spec as last time," he confirmed. "It is already a little bit faster than last year's engine and we are waiting for some new parts to arrive in time for the first race. The pneumatic-valve engine also helps in acceleration; it is a little bit easier to ride. It has a lot of potential."

Testing at Sepang will continue on Wednesday and conclude on Thursday.