The belt is probably worn out for starter, Put the rear axle on jack stands to see if the clutchs are working correctly. The front should close up at the same time as the rear opens up to change gear ratios. If you have to put a new belt on, get the shorter performance belt as it will give the old girl alittle more power and pickup. See here:
http://www.mfgsupply.com/m/c/HP3004.html. Then get back to us.