Steering head bearings - question

[schnowz]

There a wrench in the GPZ toolkit under the seat for adjusting the steering  bearings. You're supposed to remove the 12mm hex cap nut and loosen the bottom triple clamp. If theres enough room and there usually is you can loosen the top triple tree instead of the bottom as it's easier to get at. 
  I doubt if the knock you're hearing is the steering bearings - could be the calipers as you suggested. If the steering bearings are loose you can feel them on a bumpy road. 
 As Bill mentioned the factory didn't grease the bearing too well and generally the bottom one will rust if you don't get in there and add grease at some point.
 
  Pete S