STEADY drizzle prevented 14-year-old Jason Sankey from completing a four-title grand slam in the Hong Kong Hardcourt Junior Championships at Victoria Park yesterday. Sankey, a Hong Kong-born Island School student, had already won the boys' 18 and under and 14 and under singles titles and the boys' 14 and under doubles title when play was halted in the boys' 18 and under doubles final because of a slippery centre court. Sankey and his fellow finalists will have to return to Victoria Park to resume their match on Thursday afternoon. On his way to the three titles yesterday, Sankey became the first player since Kelvin Ng in 1977 to win the boys' 18 years and under title when he was still qualified to play in the 14 and under age group. And Sankey's efforts yesterday made up for lost time as he missed last season's event because of a broken arm, suffered playing rugby. ''The injury happened in November 1992,'' said Sankey. ''I was running with the ball and tried to pass it when I was tackled. Then another player fell with his knees on my left arm. I couldn't play here last year because of the injury but this has made upfor it.'' Following the break, a plate and five pins were inserted in his left forearm in an operation which required 50 stitches up each side of the arm. The plate comes out in May and he will have a short break before heading for a European tour in July with his coach, Michael Walker. One of the spin-offs of the injury has been a re-modelled back-hand, doing away with the double-fisted style because of his injured left arm to the more classic single-handed backhand. Sankey, who turned 14 in February, was the favourite in the 14 and under singles and justified his top seeding by beating Wayne Wong, the second seed, 6-4, 6-4. In the 18 and under championship, Sankey was seeded third behind top seed Bill Young and Yu Kwok-ming. Young withdrew because of injury and Sankey disposed of the second seed, Yu, 6-1, 6-2 in the semi-finals to set up a final against unseeded Australian qualifier Mark Hiscoke. Sankey had to work hard for his 7-5, 6-3 success. In the boys' 14 and under doubles, Sankey teamed up with Wayne Wong and beat Karlson Wong and Desmond Chen 6-3, 6-1. In the girls' events, Jacklyn Fu, the top seed, beat fifth seed Rebecca Hawkes 6-3, 6-3 in the 18 and under final. Fu and Alexandra Kleffel won the 18 and under doubles final 7-5, 7-6 (7-5) against Lorraine Ng and Yan Sin-man. In the girls' 14 and under singles final, second seed Tong Ka-po beat Jackie Hawkes, the fourth seed, 6-2, 6-2. Tong teamed up with Natalie Banday to beat Lam Po-kuen and Chan Wai-yan 6-2, 6-2 in the final of the girls' 14 and under doubles competition.