MotoGP title leader Jorge Lorenzo rode an all-black 2013 Yamaha M1 prototype during Monday's Brno test, but didn't find any improvement over his present machine.

The new bike featured a new chassis, fitted with the present engine, meaning it would be theoretically possible to race the machine this year without influencing the MotoGP engine-change restrictions.

However Lorenzo feels it needs further work.

"We tried the new chassis for next year. For the moment it is a prototype, not the final chassis," he said. "For the moment we didn't find any improvement, any positive things, so we still have some work to do."

Lorenzo is now just 13-points ahead of Honda's Dani Pedrosa, after suffering a last turn defeat in a thrilling conclusion to Sunday's race. Pedrosa has been racing a 2013 prototype since July's Laguna Seca round.

Meanwhile, Lorenzo and his crew were able to make improvements to the present M1 on Monday, with which he set his best lap time.

"We worked on braking which was where I struggled with Dani during yesterday's race. We found something a bit better which should help us gain some tenths of a second," said Lorenzo.

Lorenzo finished the test in third place, a few tenths behind Tech 3 Yamaha riders Cal Crutchlow and Andrea Dovizioso. Pedrosa was fourth.

Further upgrades for the 2013 M1 are expected to be made available for next week's Aragon test.

Lorenzo's team-mate Ben Spies, who will be replaced by Valentino Rossi for 2013, did not try the new bike.

""There was not so much for us to do today, we spent some time this morning working on the base set up of the bike which completed our test schedule," said Spies, who was seventh fastest.

"We'll go to Aragon next week to continue and see if it helps us for the next race in Misano."