Ben Spies made a promising start to his factory Yamaha career by setting the third fastest lap time during testing at Valencia on Tuesday.
The 2010 Rookie of the Year spent the majority of the day riding a prototype version of next year's YZR-M1.
The American rider and his crew used their inaugural session to focus on the chassis settings of the new bike, delivering consistent fast laps to end day one 0.866sec behind team-mate and world champion Jorge Lorenzo, but just 0.103sec behind new Honda rider Casey Stoner.
Spies beat his best lap time in Sunday's Valencia Grand Prix by 0.416sdec.
"For the first day of testing I'm super happy with the team, a lot of things are new including obviously riding the prototype bike," said Spies. "There are a lot of subtle changes from last year so I spent some time getting used to it along with working with a new Japanese engineer who is very, very good.
"I had a couple of new mechanics who were learning the ropes as well so it was a lot of learning today. I'm really happy, I can feel the potential of the bike and I think there's quite a bit more to come."
Tuesday was also the first day of track action for new team manager Massimo Meregalli.
"As a first day, I think Ben's crew worked really well," said the Italian, who guided Spies to 2009 WSBK title success. "He was very satisfied with the new 2011 prototype YZR-M1 bike which is a good sign.
"We didn't make many changes to the setup in the session so it's clear that we have a good base to work with. Tomorrow we will start to test the 2011 tyres as today Ben used the same ones as he ran for Sunday's race."