And one I've not seen mentioned so far- the battery. Had a clunk in mine for months on bumps, bought all the steering head bearing tools but found nothing wrong nor any improvement after resetting. Checked all the rest of the suggestions here to no avail.
Recently installed some electric gear requiring me to finally access the battery and lo and behold the 2 piece battery clamp was very loose allowing the battery to bounce around on impacts. No more clunk after tighting it up.