Bad Request when adding new post via ajax form

Finally found the problem. The action: save_post was missing from data in ajax call. This code works:

  <script>
    jQuery( document ).ready(function() {
        jQuery('input[type=button]').on('click', function() {
            var ajaxurl = "<?php echo admin_url('admin-ajax.php'); ?>";
            jQuery.ajax({
                type: "POST",
                data: {
                    data:jQuery('.event-form').serialize(),
                    action: 'save_post'
                },
                url: ajaxurl,
                success: function(result) {
                    console.log('data sent!');
                    console.log('sent to: ' + templateDir + loadUrl );
                },
                error: function(jqXHR, textStatus, errorThrown) {
                    console.log(jqXHR + " :: " + textStatus + " :: " + errorThrown);
                }
            });
        });
    });
   </script>