Dani Pedrosa and Casey Stoner were forced to miss the second day of MotoGP testing in Malaysia due to engine and weather problems.
Pedrosa's Honda RC213V bike developed a problem on Monday and his engines were sent to Japan for analysis.
The engines arrived back on Tuesday, when the Sepang circuit was drenched by heavy rain, meaning that Pedrosa and Stoner were unable to ride.
The Yamahas of Ben Spies and Jorge Lorenzo ended the day fastest.
Pedrosa and Stoner are due to return to the track on Thursday for the final day of testing.
Stoner, the defending MotoGP champion, had topped the timesheets on a weather-affected first day of pre-season testing.
Lorenzo, the 2010 champion, was pleased with the progress he had made in the wet conditions.
He said: "We were able to try the 1000cc bike on the wet for the first time and we went very fast so it's been a positive day and we are very motivated to improve the bike more."
A further test is scheduled for Jerez in Spain (23-25 March), ahead of the first race of the 2012 season in Qatar on 8 April.