The second round of the Open is underway at The Australian GC with a thick blanket of smog still hovering over Sydney.

The overnight pacesetters, amateurs Chun-An Yu (through four holes) and Takumi Kanaya (12.10pm AEDT), are still tied atop the leaderboard on Friday at six under par.

But several players have already made early moves, including young Australian David Micheluzzi, who has picked up four strokes to race to five under.

He is tied with American Cameron Tringale and Australian veteran Rod Pampling.

England's Paul Casey, among the tournament favourites, has picked up a shot through five holes to move to four under.

Also at four under and due to tee off later in the morning is former Open winner Matt Jones, as well as Dimi Papadatos and Daniel Nisbet.

Speaking after Thursday's first round, Japanese sensation Kanaya refused to get ahead of himself despite upstaging the star-studded Open field.

"I have a little confidence but I have three more days so I will do my best tomorrow," Kanaya said.

As Open favourite Adam Scott floundered with a 75 on day one, Kanaya, the world's top-ranked amateur, carded a stylish 65.

A winner last month in his homeland, 21-year-old Kanaya's sizzling round comes four years after he signed for an 85 at The Australian while on his Open debut at the same venue.

Jones, a long-time member at The Australian GC, complained of burning eyes from the smoke blowing in from NSW's surrounding bushfires following his impressive start.

"It's awful," Jones said on Thursday.

"The smoke's not good at all. It's tough to see your golf ball when you're out there playing, where it finishes. Your eyes do burn up.

"I've got that cough like you've got something in your lungs, phlegm in your lungs or whatever, but yeah it's not fun.

"I hope my kids are inside in the hotel room."

Jones won the Open at The Australian in 2015 and also finished second in 2017.

Pre-tournament favourite Scott, whose 75 was his first start to an Open since 2010, hopes to avoid an embarrassing missed cut and has helped his quest by picking up three early birdies.

Scott is at one-over-par midway through his front nine on day two.

Scott's fellow big-name Australians Cameron Smith (68) and Marc Leishman (69) are both off at 11.50am.

Australian Associated Press