Seven-time MotoGP champion Valentino Rossi is delighted to have the chance to make his 400th grand prix start at Phillip Island.

Rossi is set to become the first rider in history to reach the milestone at this weekend's Australian Grand Prix and the Monster Energy Yamaha star was in a reflective mood.

The Italian, who has claimed nine titles across all classes, has taken part in 42.5 per cent of all motorcycle grand prix events since the start of the world championship in 1949, scoring points in 353 of his 399 starts.

"It's been a long, long time," said Rossi. "It's something you don't expect, especially when I was young, but in my career I've never had a clear idea of what will happen or how long I have to race.

"When I was 17 you see a guy that is 25 years old and it felt like your grandfather! Now I am 40, imagine!

"It's a good achievement because I didn't know what to expect when I started my career.

"It is good to make the 400 here in Phillip Island as it is an iconic place for MotoGP and all the riders love the circuit because it is something special compared to the rest. It is one of the best places."

While the riders got to enjoy the sun around media activities on Thursday, rain is forecast for when they take to the track across the weekend.

"We pray, everybody prays, for the weekend weather to be like this with the blue sky and fantastic temperature," said Rossi.

"Unfortunately, the good weather has arrived a little bit too much in anticipation of the weekend so we will have to fight with difficult conditions at Phillip Island. Anyway, it is always a pleasure."