Hello from upstate New York. Continuing the rebuild this YGS-1 and I have maybe a silly question about the clutch. I am not sure if I should be tightening the 6 bolts on the pressure plate all the way down or if I should be tightening to some measured gap.

Yes tighten fully. The spring stubs move through when clutch is operated. It's all a bit back to front compared to the usual clutch on bigger yamahas. Cheers.

I'd say "snug fully" like with a screwdriver.  They don't need to be very tight and tend to break off when tightened too much.  Don't ask me how I know. 

Yep! That did it. Thanks folks.