Aprilia's Marco Melandri encountered chassis set-up issues with the RSV4 as the Italian returned to action for the first time since the winter break in Portugal.
Melandri completed three days of testing at Portimao, working alongside Aprilia's test rider Alex Hoffman as Sylvain Guintoli recovers from a second operation on his right shoulder, which the Frenchman injured last season.
Rain and low temperatures on the first two days of the test stifled Melandri's progress, but the ex-MotoGP rider took advantage of better conditions on the final day on Monday.
Aprilia's new signing made good headway with the electronics, but faced some challenges with the RSV4's chassis, setting a fastest lap revealed by Aprilia of 1m 43.1s with Hoffman managing a time of 1m 45.0s.
Melandri said: “Considering the difficult weather conditions, the first two days were a bit wasted. We made a lot of progress with the electronics but we had a few problems with the chassis set-up.
“The track improved little by little and the settings had trouble coping. Toward the end of the test we began to figure out which direction to go for my riding style, but it's a shame that we lost the last half hour [due to oil on the track] where we could have tried to put in a fast lap,” he added.
“I'm disappointed about that but the good thing is that we have a clearer idea now. I hope we can get back onto the track for some more testing before the first round at Phillip Island.”
Aprilia expects Guintoli, meanwhile, to return in time for the opening race of the 2014 season at Phillip Island in Australia on February 23 after a period of physiotherapy.