Remove logo, updates,comments, new content from admin bar.

add_action( 'admin_bar_menu', 'l7w_remove_wp_logo', 999 );
function l7w_remove_wp_logo( $wp_admin_bar ) {
    $wp_admin_bar->remove_node( 'wp-logo' );
    $wp_admin_bar->remove_node( 'updates' );
    $wp_admin_bar->remove_node( 'comments' );
    $wp_admin_bar->remove_node( 'new-content' );
}