After a late start, new six time MotoGP world champion Valentino Rossi experienced an early version of Yamaha's 2009 YZR-M1 - and the new single-tyre spec Bridgestones - during Monday's opening day of testing at Valencia.

Despite completing the least laps of any rider present, 40, the Italian was third fastest with a time of 1min 32.921secs. That time was 0.154sec quicker than his best lap in Sunday's race but 0.457sec behind Monday's pace setter - and Sunday's race winner - Casey Stoner.

Rossi began with two runs of six laps each with his 2008 M1 in order to check some settings and also get a feel for the new tyres. The Italian, sporting a special testing helmet, then made five runs and a total of 28 laps on the new prototype, setting his best time on the second run.

"Today we began work on 2009 and I was able to try the new bike for the first time. It is only the first prototype but my impression of it is very good and it seems they have done a good job," declared Rossi.

"We are working on the engine in order to have more acceleration on the exit from the corner and there is a small change, not enough yet but in the right direction so this is important. We worked on the setting and the weight distribution and I was faster with the new bike so this is good!

"We need more time to understand the bike and more laps but this is only the first day and it is very positive."

Rossi and some other riders had previously expressed concern that Bridgestone's plans to allow only 20 tyres per rider at each race weekend next season - and only two different compounds - would cause problems, but he was pleasantly surprised by the new 'one size fits all' rubber.

"The other 'big' thing today of course is the new tyres and I am really happily surprised," he admitted. "This is not the best track to try them at as we don't have so much data for here but anyway they feel very good. I was expecting less grip but we had a lot and everyone was fast today.

"The track conditions are a lot better today than they have been during the weekend so this makes a difference, but anyway we can already see that they are quite good. I think Bridgestone have done a good job but of course it will be hard to know for sure until we have been to some different tracks.

"We have to wait and see. For me they feel good even in comparison with my Bridgestone tyres from all of the season so I am happy so far.

"I have a special 'world champion' helmet now which I like a lot and which I will use throughout the winter testing. As for the number one... I will keep my 46 of course but I will put the number one on my back as I did in the past," he revealed.

Rossi's Fiat Yamaha team-mate Jorge Lorenzo was seventh fastest in a time of 1min 33.550sec after his first day with Bridgestone tyres.