how do I fix my rototiller?

I have an older 8hp chain drive front tine tiller that does not want to dig anymore. It starts fine, but when I start to till, the tines will not keep turning. They turn fine in mid air. Could the belt be "glazed" so much that it is just slipping? Or could it be something with the chain? The tiller was sold by JC Penny. It has a "few" years on it, but the engine still runs strong