Take the belt off, run it and watch the RPM that the clutch starts to close. If your careful you should see it start to move at the same rpm every time. The belt may bring that rpm down from the drag of it, but if it is stock, I would say it shoud engage at about 3600-3800. Normally a worn belt will engage at a higher rpm as the clutch has to come in farther to grab it. If the spring is getting sacked out, the rpm will drop for engagement, as the spring becomes easier to overcome. If the clutch seems to jump and grab the belt suddenly, I would suspect a grooved flyweight in the clutch. It should be a smooth engagement. And yes, the belt shoud sit level in the secondary, although there is adjustment in the sheaves (the three bolts on the outside with the sliding ring) Make sure it is adjusted for the new belt, if its too tight, it will drag, squeal, and possibly try to move at idle.