Scott Redding felt no ill effects from his wrist injury as the British prospect chalked up 48 laps on the Go&Fun Gresini Honda RCV1000R at the Sepang MotoGP test.
Redding suffered a broken wrist following a heavy spill during qualifying for the Australian MotoGP in October, but the series rookie felt back to full strength as he returned to pre-season action in Malaysia.
His fastest lap of 2m 04.431s left him in 21st position and Redding is now looking forward to the second day of the shakedown.
America's Nicky Hayden was the leading rider on Honda's new production racer, lapping in 2m 03.319s to end the opening day in 17th place.
However, it was Aleix Espargaro who set the 'Open' class alight on the NGM Mobile Forward Racing FTR-M1, lapping in 2m 01.419s to post the seventh fastest lap.
Redding said: “This first day of testing was good, I was really happy to ride again at full strength, without physical problems, although it was hard for me to ride all day because of the weather conditions.
“The bike was working well, I like riding it, but we need to improve on the electronic and braking. Tomorrow we will focus on set-up, in order to make the bike turn better.”
Redding's team-mate, Alvaro Bautista, was fifth fastest on the factory RC213V.