[Hammarlund] HQ150 Bandspread dial problems

[na2x at yahoo.com]

I have a HQ150 I'm trying to get into working shape and I'm having problems where both the general coverage dial and the ham band bandspread dials are slipping.   As I turn either big knob, there's part of the rotation where the plastic dial slips

Is there an adjustment that I need to know about to correct this?  I notice there's a nut on the back of the flywheel. Does this have to be tightened a certain amount to apply the right pressure on the pulley that the plastic dial rides in so that it rotates smoothly as the knob is turned?

Thanks for any hints. HNY everyone,
Bob