Yamaha duo Valentino Rossi and Jorge Lorenzo fear the loss of mileage in tonight's rain-affected Qatar test could prove costly for them.
Few ventured out early in the session as strong winds had brought a great deal of dust onto the circuit, and then a rainstorm prevented any further meaningful running until the closing stages.
Although some riders managed to set quicker times late in the evening, the Yamaha team chose to stay in their garages.
Rossi said the weather had been a particular blow given that he had struggled for pace in Qatar in 2008.
"Five minutes of rain really gave us a lot of problems today," said the world champion.
"First we waited and then finally we decided to abandon it. I hope tomorrow it's back to normal because this was our worst race last year and we need the time to see where we are and continue to improve with our new package."
His teammate Jorge Lorenzo had also been desperate for the Losail track time, having had difficulty with the 2009 Yamaha in the previous test in Malaysia.
"I went out and on the third lap it started to rain - I couldn't believe it," said Lorenzo.
"It seems strange to have rain in the desert and it's been a nightmare for the team because we have lost a whole day.
"I hope it's better tomorrow because I really want to try the new electronic system and also I need to keep working to improve with the Bridgestone tyres."