it could be loose steering head bearings
put the bike on a stand so the front wheel is off the ground
then grab the front wheel and pull forwards and backwards, get someone too look or feel if there is movement at the top or bottom of the steering head bearings.
you are looking for differential movement between the steering front tube (frame) and the triple clamps.
tighten the bearings and replace them if they are notchy.
never overtighten steering head bearings, you want the wheel to move freely from side to side with just a slight tension.
some mechanics see if the wheel will just fall from centre to lockon its own, that is usually enough.
jkwobble brisbane
October 2008