Marlboro Ducati's Valentino Rossi may switch back to the original Desmosedici GP11 MotoGP bike after a back-to-back test with the GP11 which the team plan to do after the Brno round.

Rossi is still mystified why he can't make the front of the GP11.1 work as well as it does with the 1000cc engine installed, admitting they don't understand the bike and saying it would be easier if Jerry Burgess was in the garage.

"This bike is very difficult to ride with the 800cc engine, it was better with the 1000cc. I did some good laptime in Mugello and Jerez and it is for this reason that we try to modify but with the 800 I can't load the front and I am very slow and we don't understand why," said Rossi.

"I think with the 1000cc we had less problem because you need to use the bike in another way so with the 1000 engine you make different lines but with the 800 you have to make better corner speed and we have more problem.

"For us it's very sad that all the fans of Valentino and Ducati are disappointed, we have to try also for them. We will speak tomorrow after the race about the GP11 and for sure make a comparison test on the Monday after Brno. I don't know if it is possible before, we don't decide yet."