I have already set "adminUI": "0.0.0.0:4985/_admin/" in my config. I still get 404 page not found when going to the endpoint (e.g. http://<host IP>:4985/_admin/).
This is the description of the config line adminUI from http://developer.couchbase.com/documentation/mobile/1.2/develop/guides/sync-gateway/configuring-sync-gateway/config-properties/index.html
URL of the Sync Gateway Admin Console HTML page. The default is the bundled Sync Gateway Admin Console at localhost:4985/_admin/.