Yamaha's Jorge Lorenzo set the pace during the opening day of the Japanese MotoGP at Motegi.
The reigning champion, who looks set to lose his title to countryman Marc Marquez, improved from third in the morning session to finish just 0.053s clear of Ducati's Andrea Dovizioso in the afternoon.
"Very positive day," smiled Lorenzo. "We finished third in the morning and then in the afternoon we improved a lot the feeling with the bike. We improved the bike in most of the corners and finally with the soft tyre we made a quite good lap time.
"This afternoon the temperature dropped a lot and that's why some riders crashed, because it was quite tricky and you need to be very careful with the temperature of the tyre.
"Our bike is working quite well and I'm in good shape, so I'm very motivated to make a good race on Sunday."
Lorenzo's team-mate Valentino Rossi, currently 14 points ahead in the fight for second in the world championship, was seventh quickest.
Yamaha has not won a race since Catalunya.