Valentino Rossi and Jorge Lorenzo, first and second in the 2009 MotoGP World Championship, were impressed by the latest prototype version of the 2010 YZR-M1 during testing at Valencia on Monday.

The Fiat Yamaha riders, second (Rossi) and third (Lorenzo) behind Honda's Dani Pedrosa in Sunday's season finale, evaluated the new machine alongside the 2009 bike - and felt clear benefits.

Lorenzo finished the day second fastest behind Ducati's Casey Stoner, with Rossi was just behind Lorenzo in third.

"I was really excited to try this new version of the M1 today and I had a lot of motivation to get back to work," said Lorenzo, who lapped just 0.025sec behind Stoner and 0.396sec under his best race lap.

"The feeling out of the corner is much better and we have more grip already in the rear so it's a big improvement for me. We still need to work on acceleration but I like what we have so far and I think we will continue to be competitive like this year.

"We have to wait and see the comparison between the old and new bike at a different track next year, but I am excited. I'm quite tired because this is already our fourth day riding here, but I am happy to have one more day of testing," he added.

Seven time MotoGP champion Rossi set a best lap time 0.166sec from Stoner and a few thousandths under his best race lap.

"It was quite hard work to get back on the bike today but it's a very important test for us," said the Italian, who was riding with a new helmet (pictured). "The new prototype we have already feels better than what we tried in Brno, so this is positive.

"I was faster than with the old bike straight away so we know we're working in the right way and hopefully we can improve some more tomorrow. Of course we still have a 2009 specification engine and we won't have an update until the next test in February, but the bike already feels more stable and has more rear grip.

"Tomorrow we have quite a lot to get through and it will be an important day before we can finally relax."