remove main site from wp admin bar

I am a super admin, when someone creates a site on the network they are automatically added to the main site and i need it to be this way.

however when that user logs in to their site the wp admin bar is on top that has a link to "my sites" with in the my sites drop down there is a link to the main site - i dont want this. i just want the user to see their sites.

the main site also shows up in wp-admin/my-sites.php

summarize... i want all new blog owners to be a user on the main site but i dont want the main site to show when they go to see all their sites.