Remove site name from title post

Check your theme (header.php). If it uses something like this :

<title><?php wp_title( '|', true, 'right' ); ?></title>

You can use this filter :

add_filter( 'wp_title', 'wpse104667_wp_title' );
function wpse104667_wp_title( $title ) {

    global $post;
    if(
       is_singular() 
       && !is_front_page() 
       && !is_home() 
       && !is_404() 
       && !is_tag()
     )
    $new_title = get_the_title($post->ID) ;
    return $new_title;
}

EDIT: add conditional tags to avoid bad conflicts