Add one or more category i.d's to this code which will exclude all posts assigned to that category from displaying in your RSS feed. http://wpsites.net/wordpress-tips/exclude-categories-rss-feed/

functions.php

function wpsites_exclude_category_feed($query) {
 if ($query->is_feed) {
   $query->set('cat','-007');
 }
return $query;
}
/**
 * @author    Brad Dalton
 * @example   http://wpsites.net/
 * @copyright 2014 WP Sites
 */
add_filter('pre_get_posts','wpsites_exclude_category_feed');