MOTORCYCLE thefts have rocketed by almost two-thirds this year with gangs cashing in by holding owners to ransom and charging up to $20,000 for a bike's return. Thefts in the territory shot up by 62 per cent in the first nine months of this year compared with the same period last year, with more machines being stolen than in the whole of 1992. Police said a large market had opened up Southeast Asia and China, despite machines above 125 cc being illegal across the border, sparking calls from owners for a new police recovery campaign. Some locally based gangs are holding owners to ransom, giving them a costly chance to prevent their pride and joy being smuggled from Hong Kong. One owner of a $150,000 Harley-Davidson had to pay thieves $20,000 to retrieve his 1,340 cc machine, stolen in the New Territories. Owners want the police to step up their liaison with the Chinese authorities in the hope of recovering more bikes smuggled across the border. The chairman of Hong Kong's Motorcycle Cruisers' Club, Alnwick Chan Chi-hing, said everyone praised police efforts to retrieve stolen cars. ''But we would hope one day that stolen Harley-Davidsons, Yamahas and Kawasakis will be returned to the territory,'' he said. In the first nine months of this year, 1,077 motorcycles were reported stolen, compared with 664 for the same period last year, and 1,070 for the whole of last year. Mr Chan said despite each of the 110 club members going to great expense to install locks and chains, motorcycles would always be vulnerable. ''Three bikes have been stolen from our members in the past two weeks,'' he said. ''They are being stolen to order and when they get to China the authorities are turning a blind eye. ''Bikes over 125 cc are illegal in China but there are lots in Guangzhou and the Pearl River delta.'' Thieves are able to deal with most locks on the market today as well as immobilisers, Mr Chan said. ''We want the police to watch out for the thieves and make better arrangements with the Chinese side. ''We know it may take some time but we want them to remember that we are victims as well as car owners.'' Mr Chan said victims would phone their contacts in the biking world and through friends of friends receive a ransom demand. Money would change hands and the owner would be told of the bike's whereabouts. He said owners were prepared to take the risk of paying ransom money rather than take out costly comprehensive insurance which covers theft. Many policies were weighted so high that few owners considered anything but third party cover. Senior Superintendent Albert Kwok Cho-kuen, of the Organised Crime and Triad Bureau, said the police were liaising through Interpol with China and Southeast Asian countries. ''We are keeping a close eye on this issue but there are a lot more difficulties with motorcycles than with cars,'' he said. ''They are easily broken down into parts for shipment and easily modified.''