Actually, not usually! Slack cable will be full advance if the cable enters the magneto housing on the left hand (engine) side looking from the contact breaker end. This is the norm on A series bikes not equipped with an automatic timing device.
The point about checking the CAMring is free to move is good though, they can sometimes get jammed.
The engine note will change considerably according to the position of the lever on the 'bars if all is working as it should. It'll run faster advanced, and slower and flat-sounding at full retard.
In normal running, most people leave the lever fully advanced 99% of the time, using retardation to start, to avoid kickbacks. With a chair on, a bit of retard on hills under heavy load might be helpful though!
