Junk-food eating Ryan Bayley has come from behind to win the Olympic gold medal in the men's sprint to continue Australia's cycling bonanza in Athens.

Bayley beat Dutch world champion Theo Bos 2-1 in the best of three final to take Australia's cycling tally to four gold medals with a day to go.

After being hauled in to lose the first race by a tyre, the West Australian reversed the roles in the second, giving up a three bike length lead to snatch the win by an even smaller margin to set up the decider.

In the third race, Bos went out hard as he did in the previous rides, but Bayley didn't let him get too far ahead and caught him on the home turn to win easily.

In the first race, Bos forced Bayley to sprint early and the 22-year-old went for it with 250m to go, stretching out to two lengths ahead, but the Dutchman steadily reeled him in and caught him on the line.

The 2002 world keirin champion at the age of 19, Bayley went into semi in sensational form.

He set the fastest time in qualifiers and in the team sprint on Saturday recorded what was believed to be the fastest flying lap in history, all fuelled on a diet of KFC and Coke.

German Rene Wolff won the bronze when he beat Frenchman Laurent Gane in two races.

Bayley beat Gane 2-0 in the semi-final, coming from three bike lengths behind with 200m to go to win the second race by an airborne wheel.

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