Casey Stoner blames the lack of an obvious Australian successor in MotoGP on the financial and legal threats facing motorcycling in his home country.

Stoner's retirement at the end of the season is set to leave a void not seen for nearly 30 years - no Australian rider seriously challenging for world 500cc or MotoGP success.

Australians have won eight premier class world titles since 1987 - Stoner winning two.

But Stoner believes having no current Australian to follow him, Mick Doohan and Wayne Gardner is down to lack of financial support for the sport's grassroots, and the need for people to put themselves in "cotton wool" because of what can happen if things go wrong.

"It's going well as far as motorsport visiting Australia, but unfortunately motorsport inside Australia doesn't have support," a frank Stoner said on Thursday ahead of the Australian Grand Prix at Phillip Island.

"There's nobody out there that's stepping up with sponsorship, or helping to find places for people to ride or start learning, or running Australian championships.

"There's a lot of tracks being closed down.

"Motorsport in general in Australia struggles to a certain degree.

"It's very disappointing. I think everybody wants to be wrapped up in cotton wool too much."

Like so many Australians aspiring to top-level world motorsport, Stoner had to leave Australia as a teenager - in his case at 14.

He was unable to race legally in Australian road races until he was 16.

So his family moved to England where he could, working through the classes to eventually become a two-time MotoGP world champion.

Stoner admits disappointment at the threat of litigation he believes is proving a deterrent to those organising the sport in Australia, and thereby stopping the prospect of unearthing more quality young talent.

"There's too many court cases pulled out because (there's) some young rider something happened to," he said.

"There's many instances like that I think are unnecessary.

"Everyone does things at their own risk, understands the risks. They should just be there to enjoy it.

"Motorcycling is a fantastic thing. It's what I grew up loving to do and will continue (socially) to do into the future, but it definitely needs a boost in Australia."

Two Spaniards - Jorge Lorenzo and Dani Pedrosa - are battling for the MotoGP crown on a grid set to become even more Euro-centric and almost certainly Australian-free with Stoner's retirement.

Practice for Sunday's Australian Grand Prix - Stoner's last as he attempts to win a sixth successive title at Phillip Island - begins on Friday.

Qualifying is scheduled for Saturday.