The 34-year-old works Honda rider has won the world championship for the past five years in succession, but there has been growing speculation that this could be his last season in road racing.
"I'm enjoying it at the moment and that's really what's keeping me in it," he said. "Every year it gets harder. When you get to the top of anything it's hard to stay there. You've got to kind of explore different ways of trying to keep yourself there and at the moment that's what I'm doing."
The New Zealander, Aaron Slight, is ready to step up the pace in front of what he calls his "home fans" in the World Superbikes' championship at Phillip Island track in Australia, also on Sunday.
Slight, often a runner-up in the past, came in third and second in South Africa three weeks ago. "I've made my best start and so I need to follow that with a win in Australia," the Honda works rider said yesterday. "It's really the home round for me and I know there will be a lot of people wanting to see me win."
The former world champion Troy Corser, from Australia, is determined to make up for what he saw as a disappointing start at Kyalami when he took a second and third in the two races.
The Australian won the title at Phillip Island in 1996 and also won there in 1995. He did much of his pre-season testing on the track in Victoria but expects the surface to have worn since then and for temperatures to be considerably cooler this weekend.
Carl Fogarty, the three-times world champion from Blackburn, leads the standings with a maximum 50 points and boasted: "It was easy at Kyalami. The other riders didn't know what had hit them."Reuse content