Yamaha's reigning MotoGP world champion Jorge Lorenzo couldn't hide his delight after finishing a close second fastest during his first 28 laps on a 1000cc MotoGP bike.

Lorenzo, who has only raced 800cc MotoGP machines, got to within 0.085sec of Honda's Casey Stoner at Monday's Brno test, which marked the public debut of the 2012 Yamaha.

For Stoner, it was his third day on the Honda RC213V and the Australian rode exclusively with next year's machine, clocking up 57 laps.

Lorenzo meanwhile switched between the 800cc and 1000cc M1s, as he also tested engine and electronics upgrades - plus different chassis and fairing parts - to try and help close the 32 point gap to Stoner in this year's championship.

Lorenzo completed 58 laps on the 800cc bike, and was fastest of the 2011 machines, by almost half a second from team-mate Ben Spies.

However Spies was much closer to Lorenzo on the 1000cc bike, lapping just 0.053sec slower to make it two 2012 Yamahas in the top three.

"Today has been an exciting and busy day because it has been the first day riding the 1000cc bike, but also because we have made a small step with the engine upgrades for the 800cc bike," said Lorenzo.

"We rode many laps non-stop from nine this morning to five this afternoon!

"I realized the 1000cc bike was incredible when I saw the power on the straight.

"I like this bike a lot and I wanted to have more laps but I have to still think about this season! I have been just one hour with our future bike!

"I can say that the next MotoGP season will be amazing, much more power, you go out of the corners sliding; I can't wait!"

Of the 17 full-time 2011 MotoGP riders, nine raced in the previous 990cc era (2002-2006).

They are Valentino Rossi, Nicky Hayden, Loris Capirossi, Dani Pedrosa, Casey Stoner, Randy de Puniet, Colin Edwards and Toni Elias.