Yamaha’s Jorge Lorenzo is determined to reassert his MotoGP world championship authority this weekend after a summer spent watching his lead get eaten away by in-form Honda rival, and fellow Spaniard, Dani Pedrosa.

Three races ago, Lorenzo had a 23-point lead at the top of the standings but Pedrosa’s successive wins at Indianapolis and then a last-corner triumph at Brno have cut his advantage to 13 points.

Lorenzo will be buoyed, however, by having won with a dominant performance at the San Marino track 12 months ago while Pedrosa admits that the Misano circuit is not one of Honda’s favourites.

“This year we’ve been very consistent, always in the first two positions. The last three races we couldn’t win, but were very close,” said Lorenzo.

“Now we arrive at this track, which for us has been pretty good for the last four years I think. I was in second the first three years, and last year I could finally get the victory.”

Pedrosa knows that the San Marino circuit will provide Honda with a different challenge to recent races.

“Misano is a tricky track, quite bumpy, with a lot of braking and acceleration. The grip level is always a challenge, because it changes a lot from the morning sessions to the afternoon,” said Pedrosa.

Pedrosa, the winner on this track in 2010, will have a new teammate with Northern Ireland’s Jonathan Rea, who currently races in the World Superbike Championship, replacing world champion Casey Stoner, who is recovering from surgery on his broken ankle.

Rea won in San Marino in Superbikes in 2009.

Nine-time champion Valentino Rossi, meanwhile, who will end his unhappy stay with Ducati at the end of the season and return to Yamaha as Lorenzo’s teammate for 2013, admitted on Thursday his time with the Italian team had been “difficult”.

“This experience, this adventure with Ducati was very difficult already from the start. And unfortunately we were not able to fix our problem during this year and a half, and I was never competitive with this bike,” Rossi told www.motogp.com.