If you have bought the property with your HRP and have paid all taxes on the sale you can just wire the funds out, no limits on the amount. However HK-Chinese citizens have to exchange it to HKD at the Chinese bank and wire it to HK. You need a copy of the contract, the tax receipts, a printout from the property records bureau showing the buyer as the new owner, a permit from the local tax bureau and a permit from SAFE (You get them in that order). Take all the document to the bank, jump a few hoops and voila. The SAFE permit has a QR code which the bank has to scan in order to proceed. Can't get around it.
Edit: You can only transfer the amount you have paid tax on. If you have used a second contract at the property office to pay lower taxes then you can only transfer the lower amount.