Australians Sam Willoughby and Khalen Young have qualified for tomorrow's BMX semi-finals with strong performances today - particularly in the crucial fourth run.

The other Australian in the field, Brian Kirkham, 26 from Adelaide, fell in each of his first two runs, and failed to make up the points required in the last three runs to make the semi-finals.

Willoughby was forced into two extra rides after missing on a countback with his first three qualifying runs.

The 20 year-old, ran fourth, first and third in his three runs over the 450m circuit at the open-air Olympic Park venue to amass eight points, the same as Latvia's Maris Strombergs, gold medallist at the Beijing Olympics.

But Strombergs won through ahead of Willoughby because he had a second, fifth and first placing in his three runs. The top points earner of Willoughby's heat was Twan van Gendt of the Netherlands, who had seven points.

Another Dutchman, Raymon van der Biezen, the fastest qualifier on Wednesday, won all three runs in the opening heat to qualify ahead of Latvian, Edzus Treimanis.

Young, 27, from Perth, fell in his first run, but recovered well to finish second and third in his next two attempts, to miss qualifying automatically by only one point. He, too, had to qualify via the two extra rides.

But after brilliant fourth runs both riders conserved energy by just going through the motions in their fifth qualifying ride, knowing they had secured enough points to get through.

However, Kirkham was eliminated from the semi-finals, despite winning his fourth run and finishing second in his fifth.

Those efforts gave him a combined total of 25 points, four points behind fourth qualifier Zabala Oquendo of Colombia.

Willoughby confirmed he had merely gone through the motions in his fifth ride, having already accumulated enough points (16) to secure third spot in his heat.

"I tried to conserve energy for tomorrow," he said. "It was a learning curve for me and I'm looking forward to tomorrow."

Young, who qualified with 19 points in the first heat, was sore after the quarterfinals and will spend time in recovery tonight, according to coach Wade Bootes.

Bootes said the falls suffered by Kirkham were part and parcel of BMX racing, and over which he had no control.

"It was a typical BMX day and some days things don't go your way," Bootes said.

"We definitely had the hard way through today. We got two people through, and they're going back to recover for four full laps tomorrow now.

"It's war out there and we're just going to take each race as a battle to get to the end out there, and whoever wants it more is going to get to the end and win.

"For Brian, it was not even his fault. People were crashing in front of him and taking him down.

"At least he showed the world he's fast enough and capable of doing things, but this sport is brutal, and you've just got to try to be aggressive out there, keep clean, and get a good lap to the finish."

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