G'day sparker
Edit: The clearance was way too much so I just did them up randomly and it's easier to start now. The surging has gone too. But I feel the clearances will wander without locking nuts.
The rocker post nuts usually have a grub screw in the centre of the adjustment nut that locks the nut
to the rocker post.
A little difficult to see in your image but the centre looks star shaped or Allen key.
Cheers
Max.
