Upvote:5
Chinese Customs operate both at harbours and airports. Should there be a restriction on bicycles, and I don't believe there is, it would apply at all ports of entry.
The reason I don't believe there are restrictions on (temporary) importation of bicycles for personal use is that I see it done every time I go to Shenzhen from HK. Cyclists, all decked in bright gear, taking their bicycles to Shenzhen to ride.