Do not disable the secure port. Rationale: The secure port is used to serve https with authentication and authorization. If you disable it, no https traffic is served and all traffic is served unencrypted. Impact: You need to set the API Server up with the right TLS certificates.
Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml on the master node and either remove the --secure-port parameter or set it to a different (non-zero) desired port. Default Value: By default, port 6443 is used as the secure port.