I think the grubscrews are there but hidden under the knob. Now that you have unscrewed the lower collar, grip the threaded part firmly but without damaging threads and unscrew the knob from the threaded part. That should then expose the grubscrews in the threaded portion as the knob is unscrewed upwards.


Doug
2011 Plus 4 in Rich Maroon

1972 750 “ComDom” sprinter
1958 Triton 650
1992 Triumph Trophy 900