Cheng Cheuk-chun blew his rivals away to win the senior men's section in the Hong Kong Cycling Association Mountain Bike Race at Kam Tim.
The 15-year-old complained afterwards that he would not be competing in this year's Asian Mountain Bike Championships in Beijing because of his age.
Cheuk-chun won the 15-lap, 22-kilometre race - one of the qualifying events for Beijing - in one hour, 12 minutes, four seconds - three minutes, 22 seconds ahead of Chung Yuet-shan.
Third-fastest was John Prosser, a further 18 seconds behind.
'You have to be at least 18 to compete in the Asian championships,' Cheuk-chun said. 'I'm quite disappointed I won't be going even if I do qualify for it. I want to show people I'm a good rider.' Hong Kong team rider Alexandra Yeung, a bronze medallist at the World B Championships in Malaysia, opted to compete in the men's race, saying she needed the longer ride to show her best form. But the move backfired as she bowed out after seven laps with cramps.
In the downhill event, Howard Tsang Chi-kong took top honours with a time of 1:16.83.
