Tom,
A broken ring could account for the blue smoke, but wouldn't account for the noise. You wouldn't hear anything from broken rings. Based on your description of the exhaust sound, I wouldn't discount anything in the exhaust system. Mufflers have a way of losing internal parts, depending on the muffler, and changing their sound as a result. Check the spark plugs for oil. A spark plug wet with oil is a bad sign.
Harvester
