Rossi rides alone as Yamaha seeks answers.

Valentino Rossi returned to Istanbul Park for testing on Monday, as he sought to understand the rear tyre problems that dropped him from second to tenth in Sunday's Turkish Grand Prix.

Rossi - whose team-mate Colin Edwards was forced to sit out the test to rest his swollen knee, injured when he was taken out on the first lap of the grand prix - completed 66 laps and spent the entire time working with Michelin, in order to gather information about Sunday's unexpected vibration problem and make sure it doesn't happen again in the Chinese Grand Prix on May 6.

Rossi's best lap was a 1min 54.0secs on race tyres, which put him 12th on the unofficial test times - but effectively matched his best lap during the grand prix, which was second only to Chris Vermeulen.

"We tried some things in order to gather information to help Michelin to understand what happened [in the race], and then tested many tyres in order to find a way forward for China," confirmed team director Davide Brivio. "We learnt a lot and we think we've found a good direction for the next race. Now Yamaha and Michelin will work on this information together and hopefully we can have a better race in Shanghai."

Brivio also confirmed that, although Edwards was absent on Monday, the American is expected to be fully fit for the fourth round of the championship.

"We decided it was better if Colin rested because he had some pain and a lot of swelling in his knee following [Sunday's] unlucky crash. It's not a serious injury but together we agreed it would be better for him to stay off the bike and save himself for China," explained Brivio. "As a result Valentino had a lot of work to do because he had to take on some of Colin's workload."