(CNN) -- Motorcycling star Casey Stoner may have announced his attention to retire from the sport on Thursday, but his apparent lack of motivation to continue racing was not apparent 24 hours later as he topped practice for this weekend's Le Mans Grand Prix.
The two-time MotoGP world champion says he has grown tired of the discipline after five years competing in the elite division, and will bow out at the end of this season -- which still has 15 of the 18 races remaining
"I will be finishing my career at the end of this season in MotoGP, and go forward in different things in my life," the 26-year-old Australian told a pre-practice news conference.
"After so many years of doing this sport which I love, and which myself and my family made so many sacrifices for, after so many years of trying to get to where we have gotten to at this point, this sport has changed a lot and it has changed to the point where I am not enjoying it.
"There are a lot of things that have disappointed me, and also a lot of things I have loved about this sport, but unfortunately the balance has gone in the wrong direction."
The Honda rider leads the 2012 world championship after two wins from three races.
"It would be nice if I could say I would stay one more year," he said. "But then where does it stop? So we decided to finish everything as we are now."
Stoner set a time of one minute 33.74 seconds around the French circuit on Friday, over two-tenths of a second quicker than Spanish teammate Dani Pedrosa.
Pedrosa's compatriot and 2010 world champion Jorge Lorenzo, who is one point behind Stoner in the standings, was almost four-tenths of a second adrift in third position for Yamaha.
Seven-time world champion Valentino Rossi was well down the order in ninth, having struggled for form since switching from Yamaha to Ducati for the 2011 season.
But despite his recent poor form, the legendary Italian dismissed rumors he was considering retirement and said he wanted to continue in the sport for at least another two seasons.
"For me it's very difficult to understand where the news starts because I never speak about my retirement," the 33-year-old said. "I want to race in MotoGP for the next two years for sure."