LE MANS, France - Struggling bike superstar Valentino Rossi heads into Sunday's French MotoGP insisting he has no intention of following world champion Casey Stoner through the MotoGP exit door.The nine-times World champion is in the worst slump of his 17-year career, having failed to register a point in this season's three races while having already endured a first-ever winless season in 2011.Defending champion Stoner stunned the paddock on Thursday by revealing he will quit at the end of the season, admitting he has lost his passion for the sport.NO THANKS TO RETIREMENTRossi, 33, insists, however, he will not join the Australian in retirement. "For me it's very difficult to understand where the news starts," he said, "because I never speak about my retirement and I want to race in MotoGP for the next two years for sure."Rossi returns to the French track where in 2011 he enjoyed his only podium spot. The Italian rider is desperate to kick-start his campaign on his under-performing Ducati."I like the track but you always have to fight with the weather," he said. "We will try to improve our performance to get closer to the guys in front of us. Last year (2011) was our best result with the Ducati here so we will see. We are optimistic."PASSION HAS GONEAll eyes will be on Stoner who said his decision to walk away from the sport was for "family reasons". The 26-year-old has won 35 MotoGP's and is leading the 2012 standings by a point after winning two of the season's three rounds.The Honda rider said: "After so many years taking part in this sport that I love, and with all the sacrifices that I have had to make, I no longer have the passion to continue and I think that it is best to stop."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 a lot of things I have loved about this sport but unfortunately the balance has gone in the wrong direction. So, basically, we won't be continuing."It would be nice if I could say I would stay one more year, but then where does it stop? So we decided to finish everything as we are now."Stoner, who also won the 2007 World title, became a father for the first time in February when his wife Adrianna gave birth to a daughter.CHANGES UNDERMINE CHAMPIONSHIPDespite his blistering start to the season Stoner has been critical of a series of technical changes to the sport that he claimed were undermining the championship. The 2012 MotoGP bikes are 1000cc as opposed to the 800cc of the previous year while manufacturers such as Kawasaki and Suzuki no longer field factory teams, leaving just Honda, Ducati and Yamaha with official squads.He has also been battling cramps in his arms that prove particularly painful under braking. Those problems came to the fore in the season-opener in Qatar, where he finished third before going on to win in Spain and Portugal.Yamaha rider Jorge Lorenzo, who won the Qatar opener and is a point behind Stoner in the standings, is keen to make the most of the Australian's waning interest in the sport. He said: "We arrive in good shape, having always been in the first two positions in the three races of the year so far. I want to keep this going in Le Mans."Last year we struggled, especially in acceleration, but I feel this year is going to be a little different. It's a good track for my riding style so we will try to fight for the win again but always thinking about the championship."