A router is not a wireless "repeater" or might not have a dedicated access point mode. You can try:
Reset the 625 back to factory defaults
Connect a cable from a LAN port of the 655 to the WAN port of 625
Connect a PC, by a cable, to the LAN ports of the 625
Log into the 625
Set LAN IP address of the 625 to an IP address on the same IP subnet of the 655 but outside of the 655 DHCP range. (SAVE but do not reboot.)
Turn off the DHCP service (SAVE but do not reboot.)
Make sure WAN port is set to DHCP.
Disconnect the cable from the WAN port.
Reboot the 625.
Connect the cable from the 655 to a LAN port
It should now be accessible on new IP address
ex:
655 --- 192.168.0.1
625 --- 192.168.0.2
You now should two routers, with one set up as an access point only. You would now need o configure the 628 wireless network. Do not use the same network SSID as the 655 one. Also, change the 625's wireless radio channel so as not to be on the same as the 655.