How to set the default values of "Included Export Components" for a Drupal Webform
I remember having to do that once, and though I looked at how the values were initially set, I still ended up using hook_form_alter to change them.
I don't remember why exactly, but presumably due to fact I couldn't reach them as easily.

Just use a hook_form_alter in a custom module to get to the form, and unset the defaults you don't want.

This should pretty much do it in a hook_form_alter or hook_form_ID_alter ( example is for hook_form_alter ) :

if ($form_id == 'webform_results_download_form') {
  /**
  * default ( and named ) components are :
  * - serial: Submission nr
  * - sid: Submission ID
  * - time: Time
  * - draft: Draft
  * - ip_address: IP Address
  * - uid: User ID
  * - username: User Name
  */
  $excludes = array('serial', 'sid');

  foreach ($form['components']['#default_value'] as $cid =&gt; $component) {
    if (in_array($component, $excludes)) {
      unset($form['components']['#default_value'][$cid]);
    }
  }
}


This will uncheck both the Submission Nr &amp; Submission ID checkbox. Adjust the $excludes array accordingly to your needs