After three sessions led by Parkalgar Honda's impressive rookie Sam Lowes, newly announced 'official' Yamaha WSS riders Luca Scassa and Chaz Davies floated to the top in Thursday's wet afternoon session.
Lowes and fellow Briton James Ellison, of the sister Bogdanka PTR team, were first and second in Thursday morning's wet outing. Lowes then improved fractionally in the afternoon, while Ellison went slower, allowing three riders to move ahead of them.
Leading the way was former World Superbike rider Scassa, whose lap time of 1min 57.074sec held off team-mate Chaz Davies by exactly 0.4sec. This week's Portimao test marks the BE1 team's debut with 'refreshed' 2009 title-winning factory R6 machinery.
Third place and top Honda went to Gino Rea of the Step Racing Team, who was also the final rider under the 1min 58sec mark. Then came reigning BSS champion Lowes and former MotoGP rider Ellison, whose team-mate Pawel Szkopek was just behind him in sixth.
Kawasaki's Broc Parkes was sandwiched in the middle of eight Hondas in seventh, as Bastien Chesaux, Miguel Praia and Florian Marino completed the top ten.
The lone Triumph of Marko Jerman was twelfth.
Testing at Portimao concludes on Friday evening.