Re: how disable buddypress header menus from main site in wordpress network mode?
You mean the BP adminbar 
Here’s how to have adminbar only in site where BP is installed.
http://buddydev.com/buddypress/remove-buddypress-admin-bar-from-all-blog-except-the-main-buddypress-site/
P.S. don’t forget to add the opening `<?php` at the top of the code
